JP2007058191A - Element, device, and method for wavelength conversion - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that a wavelength converting element which has high conversion efficiency and is suitable as a high-power light source can not be obtained though a great deal of effort is put for improvement of a wavelength converting element itself, since there are many problems such that a bulk type wavelength converting element has low conversion efficiency, a waveguide type having high conversion efficiency has problems when having high power and also has difficult constitution conditions when an element length is made long to increase conversion efficiency, and a resonator type need to have its resonator length adjusted according to a wavelength. <P>SOLUTION: In addition to improvement of the wavelength converting element itself, light convergence conditions of a way of converging incident light by a light convergence optical system which has not been taken into account so much are managed so that the light may be converged on an intermediate point of an optical path and the volume of the incident signal light beam may be minimized. Consequently, the wavelength conversion efficiency is made higher to provide a light source which has a simple structure and is usable even as a high-power light source at a low price. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In the present invention, the wavelength is different from the first wavelength λ1 from light having a first wavelength λ1 (including light other than visible light such as infrared light, etc., which is incident below) incident on a wavelength conversion element body described later. An element itself capable of performing wavelength conversion to light of the second wavelength λ2 is also referred to as a wavelength conversion element body, and an optical system or the like disposed in the wavelength conversion element body or the wavelength conversion element body as a case or the like. The mounted one is also called a wavelength conversion element. Moreover, although the apparatus which has a wavelength conversion element is called wavelength conversion apparatus, a wavelength conversion apparatus may be substantially the same as a wavelength conversion element depending on the mode of a structure.

  The present invention is a wavelength converter capable of causing light having a first wavelength λ1 to enter the wavelength conversion element body and outputting light having a second wavelength λ2 different from the first wavelength λ1 from the wavelength conversion element body. The present invention relates to a wavelength conversion element having an element body, a wavelength conversion device using the same, and a wavelength conversion method.

  Coherent light sources are indispensable not only in the optical communication field, but also in the medical field and the measurement field such as a microscope. As for the wavelength of the coherent light, for example, in the medical field, various wavelengths are used depending on the purpose, and are being used more widely.

  Various types of laser oscillators including semiconductor lasers are known as light sources for coherent light. However, some light sources cannot be obtained directly from a laser oscillator depending on the wavelength. In that case, for example, nonlinear wavelength conversion is used in order to obtain a necessary wavelength.

  For example, wavelength conversion based on quasi-phase matching of polarization inversion elements such as PPLN (Periodically Poled LiNbO3) and PPKTP (Periodically Poled KTiOPO4) has a relatively high wavelength conversion efficiency, and an SHG wavelength from a 1 μm band to a visible light band near 500 nm. Widely used in conversion and so on.

  Many proposals have been made on wavelength conversion methods and wavelength conversion elements for obtaining short-wavelength coherent light.

  FIG. 12, FIG. 20, FIG. 24 of Japanese Patent Laid-Open No. 2002-99009 (hereinafter also referred to as Patent Document 1), FIG. 12, FIG. 20, FIG. 24 of Japanese Patent Laid-Open No. 2002-250950 (hereinafter also referred to as Patent Document 2) In FIGS. 12, 20, and 24 of 2003-295242 (hereinafter also referred to as Patent Document 3), light from a laser light source is collected by a lens and incident on a wavelength conversion element to perform wavelength conversion. Are listed.

  Patent Documents 1 to 3 are applications by the same applicant and have many common parts, both of which are priority applications of Japanese Patent Application Nos. 6-206748 and 6-307410.

  FIG. 9 is a wavelength conversion element described in FIG. 20 of Patent Document 1. Reference numeral 1100 denotes a wavelength conversion element, 209 denotes a domain-inverted region formed on a LiTaO 3 substrate having a thickness of 0.2 mm doped with MgO or the like. Is a groove formed by etching the substrate 100 nm (described as being effective in forming a uniform domain inversion region), 219 is an antireflection film, 221 is a laser, 222 is a condensing optical system, and 223 is The fundamental wave, 224 is the second harmonic, 225 is the entrance surface, and 226 is the exit surface.

  In paragraph 0289 of Patent Document 1, the fundamental wave 223 emitted from the laser 221 in FIG. 9 is condensed and incident on the incident surface 225 of the wavelength conversion element 1100 by the condensing optical system 222, and the inside of the wavelength conversion element 1100 is entered. It is described that the wavelength conversion is performed by propagating and the light is emitted from the emission surface 226 as the second harmonic 224 having a half wavelength of the fundamental wave 223.

  FIG. 10 shows the wavelength conversion element described in FIG. 12 of Patent Document 1, and the light (fundamental wave) 223 of the semiconductor laser 221 is obtained by using the periodic domain-inverted region 209 formed in the substrate 201 as it is in the bulk state. Is incident through the condensing optical system 222, and is subjected to multiple reflection by the reflection films 214 on both end faces of the substrate 201 (the reflection film 214 reflects 90% or more of the fundamental wave having a wavelength of 800 nm) to resonate inside the substrate 201. It is described that it is converted into the second harmonic 224 with high efficiency and output.

  In both the cases of FIG. 9 and FIG. 10, the details of the condensing of incident light by the condensing optical system 222 do not seem to be particularly important and are not described in the text. Each is a figure that can be received as if it is focused on the incident surface.

  FIG. 1 of Japanese Patent Laid-Open No. 2004-280019 (hereinafter also referred to as Patent Document 4) describes an optical parametric oscillator shown as FIG. 11 in the specification of the present invention. In FIG. 11, the pumping light pulse train from the pumping light source resonator 101 is focused into the nonlinear crystal 106 by the lens 104, and signal light and idler light are generated by the nonlinear crystal 106. The idler light passes through the condenser mirror 107. The light is taken out of the resonator, and the signal light is reflected by the condensing mirror 107 to be approximately parallel light, passes through the end mirror 108, reaches the output coupling mirror 109, and a part thereof is output as the output coupling mirror 109. The remaining extracted signal light reaches the condensing mirror 105, and then the resonator of the condensing mirror 105-the nonlinear crystal 106-the condensing mirror 107-the end face mirror 108-the output coupling mirror 109-the condensing mirror 105-. Keep going around. During this circulation, as described above, when the signal light reaches the output coupling mirror 109, a part thereof is taken out as an output. When the signal light makes 3/2 rounds of the resonator, the next excitation light pulse enters the nonlinear crystal 106, and as a result, another signal light is generated in the resonator.

  The polarization inversion wavelength conversion element includes a bulk type and a waveguide type.

  In the bulk type, as in Patent Documents 1 to 3, input light (incident light) is collected by a lens and input to an element, and wavelength conversion is performed under a condition of light density corresponding to the beam propagation profile. .

  In the waveguide type, the input light is coupled to the waveguide of the element by a lens or the like, and wavelength conversion is performed under a condition of light density corresponding to the waveguide mode diameter.

  In both types, as the element length increases, the interaction length with the input light increases and the conversion efficiency increases. However, the optical density of the waveguide type is constant regardless of the element length, whereas the bulk type As the element length increases, the optimum light collection diameter increases and the light density decreases. For this reason, basically, the waveguide type has a higher conversion efficiency in proportion to the square of the element length, whereas the bulk type has a higher conversion efficiency in proportion to the first power of the element length. .

  The waveguide type has higher conversion efficiency, but if the input / output power is at the watt (W) level, the light density becomes too high, which may cause problems such as damage to the device, resulting in high output. Many of the bulk types are also used in applications.

  In the wavelength conversion using the quasi-phase matching of a bulk type polarization inversion element that is conventionally used, as shown in FIG. 12, the incident light is incident on the polarization inversion element 211 in which the polarization inversion region of the wavelength conversion element 200 is formed. 204 is incident from the input end where the antireflection film 202 is disposed, and the incident light 205 is passed through the polarization inversion element 211 to perform wavelength conversion, and from the output end where the antireflection film 203 of the polarization inversion element 211 is disposed. The output light 206 after wavelength conversion is emitted.

  Even in the case of SHG wavelength conversion using a polarization inversion element such as PPLN or PPKTP, if the input light in the 1 μm band is continuous light (CW light) of ˜1 W level, the conversion efficiency to the 500 nm band is several percent, and most of the input Light passes through the polarization inverting element without being converted.

  In order to increase the conversion efficiency, a waveguide-type polarization inversion element that can increase the light density in the element may be used. However, there is a problem that the beam quality of the output light deteriorates, or the input as described above. However, at high power of ˜1 W level, there is a problem that the light density becomes too high and damages the device.

A method for increasing the conversion efficiency by increasing the element length has also been proposed, but the wavelength efficiency of the conversion efficiency has a wavelength characteristic. As the element length increases, the allowable wavelength range becomes narrower, so that the wavelength condition of the input light becomes severe.
Between the allowable wavelength range Δλ and the element length L, there is a relationship Δλ × L = constant. In addition, when the element length is increased, it is difficult to form a uniform domain-inverted structure over the entire element.

  Japanese Patent Laid-Open No. 10-260438 (hereinafter also referred to as Patent Document 5) performs wavelength conversion by turning back the signal light that has reached the end of the element and re-entering the element while keeping the dimensions of the element small. It has also been proposed to increase the effective length of the device, but it seems that it was not considered to be so good, and the details for practical use were not stuffed.

  A method is also used in which a resonator is configured so that the input light is confined in it, and the conversion efficiency is effectively increased. The conversion efficiency may be several tens of times that of a normal configuration. However, it is necessary to control the resonance frequency of the resonator in accordance with the wavelength of the input light, and it is necessary to detect the detuning component and to perform feedback control thereof.

  Concerning a condensing method when incident light is incident on the wavelength conversion element, in the case of a waveguide type wavelength conversion element, the incident light is condensed and incident. In the case of a bulk type wavelength conversion element, as described in Patent Documents 1 to 3, it is described that incident light is condensed on the incident surface of the element by a condensing optical system. Is not considered to be a particularly important problem, or there is no further detailed description.

JP 2002-99009 JP2002-250950 JP 2003-295242 A JP2004-280019A JP-A-10-260438

  As described above, in each application field, it is strongly desired to realize a wavelength conversion device and a wavelength conversion method that have a simple structure, high conversion efficiency, high light output, and low cost. Wavelength conversion by the bulk type wavelength conversion element possessed has low conversion efficiency, and wavelength conversion by a waveguide type having a relatively high conversion efficiency has a problem in achieving high power. If the element length is increased in order to increase the conversion efficiency, the configuration condition becomes difficult, and the resonator type must be adjusted in accordance with the wavelength.

  Although various attempts have been made to improve the wavelength conversion efficiency with respect to the wavelength conversion element, it is the present situation that a wavelength conversion element suitable for practical use cannot be obtained particularly in high power applications.

  For high power applications, increase the conversion efficiency by constructing a wavelength converter by connecting multiple bulk type wavelength conversion elements with polarization inversion regions in series along the optical path using a condensing optical system Can be considered.

  However, an inexpensive wavelength conversion device and wavelength conversion method have not yet been realized with a simple structure, high conversion efficiency and high light output.

  As described above, great attention has been paid to the improvement of the wavelength conversion element itself, but the condensing optical system in which the converted light is incident on the wavelength conversion element that performs wavelength conversion is not so important. The current situation.

  The present invention has been made in view of the above points, and one of the objects of the present invention is to improve the state of a condensing optical system that makes converted light incident on a wavelength conversion element, and to have a simple configuration. Accordingly, an object of the present invention is to provide a wavelength conversion device and a wavelength conversion method capable of further increasing the wavelength conversion efficiency and enabling high light output.

  The present invention has been made to solve the above problems.

  As a means for solving the above-mentioned problem, a special feature of the basic idea of the technology used in the present invention is that a condensing optical system when a signal light that has been wavelength-converted conventionally is incident on a wavelength conversion element, has a wavelength. In the present invention, the light that has been focused on the incident surface of the conversion element, or that portion was not strictly managed, is converted into a wavelength conversion element by a condensing optical system as described later. The method of condensing the incident light is managed in a particularly preferable state so that a high-quality, high-output wavelength converted light can be obtained.

  Hereinafter, the present invention made to solve the problems will be described more specifically.

  In the present invention, wavelength conversion is performed on light having a first wavelength λ1 included in incident light incident on a wavelength conversion element body, which will be described later, to light having a second wavelength λ2, which is a wavelength different from the first wavelength λ1. The element itself that can be used is called the wavelength conversion element body, the end of the wavelength conversion element body that makes incident light incident on the wavelength conversion element body is defined as the incident end, and the incident light enters the wavelength conversion element body. The wavelength converting element main body travels while undergoing wavelength conversion from the light having the first wavelength λ1 to the light having the second wavelength λ2, and includes light having the first wavelength λ1 and light having the second wavelength λ2. An end portion different from or near the end portion of the wavelength conversion element main body that reaches as light is defined as a reaching end portion of the wavelength conversion element main body, and the wavelength conversion is performed in the reaching end portion. The end that takes out the light that arrives and receives it as the outgoing light Defines the vicinity of the end as the exit end of the wavelength conversion element body, and the incident light including the light of the first wavelength λ1 before entering the wavelength conversion element body and the incident light enter the wavelength conversion element body The incident light including the light having the first wavelength λ1 and the light having the second wavelength λ2 that travels in the wavelength conversion element body while being subjected to wavelength conversion, and the incident light incident on the wavelength conversion element body are the wavelength conversion element. Each of the emitted light that travels through the body and is subjected to wavelength conversion and emitted from the wavelength conversion element main body, or these are collectively referred to as signal light, and an optical system or the like disposed in the wavelength conversion element main body or wavelength conversion A device in which an element body or the like is mounted on a case or the like is referred to as a wavelength conversion device, and is also referred to as a wavelength conversion device. Further, in the present invention, for the convenience of explanation, the expression that distinguishes the wavelength conversion element main body from the wavelength conversion element is taken. However, on the commercial side, a condensing optical system is provided outside the wavelength conversion element main body. Since it is obvious that the effect of the wavelength conversion element of the present invention can be exerted by using the arrangement, even in the case of only the wavelength conversion element main body, etc., with respect to the wavelength conversion element main body with a reflection film etc. These are included in the wavelength conversion element of the present invention.

  A wavelength conversion device according to a first invention (hereinafter also referred to as invention 1) as an example of the present invention is a wavelength conversion device using at least two wavelength conversion elements, and the wavelength conversion device is subjected to wavelength conversion. At least one wavelength conversion optical circuit unit having at least two wavelength conversion elements connected in series via a lens (hereinafter also referred to as a connecting lens) in the optical path of the signal light beam. At least one of the wavelength conversion optical circuit units of the device is one of the two wavelength conversion elements connected in series via the connection lens (hereinafter also referred to as a first wavelength conversion element). The optical path of the signal light beam including the optical path passing through the connection lens between the emission end of the light source and the incident end of the other wavelength conversion element (hereinafter also referred to as the second wavelength conversion element) is also referred to as a connection lens optical path. Accordingly, the signal light beam emitted from the first wavelength conversion element passes through the connection lens optical path and is condensed at a predetermined position of the second wavelength conversion element by the connection lens. It is comprised so that it may inject into a wavelength conversion element, The said predetermined position of a said 2nd wavelength conversion element is the incident end part and output end part of the wavelength conversion element main body which comprises the said 2nd wavelength conversion element During this period, the signal light beam that has reached the reaching end portion or the signal light beam that has exited from the reaching end portion is reflected by a reflector disposed at or near the reaching end portion, and is incident again on the same wavelength conversion element main body. In the case where a reflector is disposed but a condenser lens (hereinafter also referred to as a re-incident lens) is not disposed in the optical path between the reflector and the end of the second wavelength conversion element, the incident end And between the exit end A reflector and a re-incidence lens are arranged between the incident end and the exit end of the wavelength conversion element main body constituting the second wavelength conversion element at or near the position corresponding to the intermediate point of the optical path length. If not, the incident position of the wavelength converting element main body constituting the second wavelength converting element is at or near the position corresponding to the intermediate point of the total optical path length between the incident end and the emitting end. When a reflector and a re-incidence lens are arranged in the optical path between the end part and the exit end part, it corresponds to the intermediate point of the total optical path length between the incident end part and the arrival end part immediately before the re-incidence lens. The wavelength conversion device is characterized in that it is at or near the position to be operated.

  A wavelength conversion device according to a second invention (hereinafter also referred to as invention 2) in which the invention 1 of the present invention is developed is the wavelength conversion device according to the invention 1, wherein at least one of the wavelength conversion optical circuits of the wavelength conversion device is provided. An incident light beam incident on the first wavelength conversion element in the unit is configured to be incident on the first wavelength conversion element so as to be condensed at a predetermined position of the first wavelength conversion element. The predetermined position of the first wavelength conversion element is a signal that has reached the arrival end portion between the incident end portion and the emission end portion of the wavelength conversion element main body constituting the first wavelength conversion element. The reflector is arranged to reflect the light beam or the signal light beam emitted from the reaching end with a reflector arranged at or near the reaching end and re-enter the same wavelength conversion element body. Body and said When a re-incident lens is not disposed in the optical path between the end portions of the one wavelength conversion element, it is at or near the position corresponding to the midpoint of the total optical path length between the incident end portion and the exit end portion, In the case where neither the reflector nor the re-incidence lens is arranged between the incident end and the exit end of the wavelength conversion element main body constituting the first wavelength conversion element, the incident end and the exit end The reflector in the optical path between the incident end and the output end of the wavelength conversion element main body constituting the first wavelength conversion element, which is at or near the midpoint of the total optical path length between When the re-incident lens is disposed, the wavelength is a position corresponding to or near the intermediate point of the total optical path length between the incident end and the arrival end immediately before the re-incident lens. It is a conversion device.

  A wavelength conversion device according to a third invention (hereinafter also referred to as invention 3) in which the invention 1 and invention 2 of the present invention are developed, the wavelength conversion device according to the invention 1 or 2, wherein at least one wavelength conversion element is: A signal light beam that has at least one re-incidence lens and re-enters the wavelength conversion element through the re-incidence lens so as to be condensed at a predetermined position of the wavelength conversion element by the re-incidence lens; The wavelength conversion element is configured to re-enter the wavelength conversion element, and the predetermined position of the wavelength conversion element is determined by the re-incidence lens of the wavelength conversion element body constituting the wavelength conversion element and the wavelength conversion element body. The signal light beam reaching the arrival end or the signal light beam emitted from the arrival end is reflected between the emission ends by a reflector disposed at or near the arrival end. When a reflector that re-enters the wavelength conversion element body is disposed, but no other re-incidence lens is disposed in the optical path between the reflector and the wavelength conversion element body. Is a position corresponding to or near the midpoint of the total optical path length between the re-incidence end immediately after the re-incidence lens and the output end of the wavelength conversion element body, and constitutes the wavelength conversion element When neither a reflector nor another re-incident lens other than the re-incident lens is disposed between the re-incident lens of the wavelength conversion element main body and the exit end of the wavelength conversion element main body, the re-incident lens And the position corresponding to or near the midpoint of the total optical path length between the re-incidence end and the exit end immediately after the re-incidence lens of the wavelength conversion element body constituting the wavelength conversion element and the Output end of wavelength converter body When another re-incidence lens other than the reflector and the re-incident lens is arranged in the optical path between the re-incident end portion immediately after the re-incident lens and the re-incident lens immediately before the other re-incident lens A wavelength conversion device characterized in that it is at or near a position corresponding to an intermediate point of the total optical path length between reaching end portions.

  A wavelength conversion device according to a fourth invention (hereinafter also referred to as invention 4) in which the inventions 1 to 3 of the present invention are developed is the wavelength conversion device according to any one of the inventions 1 to 3, wherein at least one of the wavelength conversion devices is the above-mentioned. In the wavelength conversion optical circuit unit, the first wavelength conversion element is disposed on one side of the connection lens optical path with the connection lens as a center, and the second wavelength is on the other side of the connection lens optical path. A wavelength conversion element is disposed, and a signal light beam emitted from one of the first wavelength conversion element and the second wavelength conversion element passes through the connection lens and is connected to the other by the connection lens. It is configured to enter the other wavelength conversion element so as to be condensed at a predetermined position of the wavelength conversion element, and the predetermined position of the other wavelength conversion element constitutes the other wavelength conversion element. Have A reflector in which the signal light beam reaching the arrival end or the signal light beam emitted from the arrival end is disposed at or near the arrival end between the incident end and the emission end of the wavelength conversion element body. When the reflector for reflecting and re-entering the same wavelength conversion element main body is arranged, but no re-incident lens is arranged in the optical path between the reflector and the end of the other wavelength conversion element At or near the condensing position that minimizes the volume of the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between the incident end and the output end. Yes, if neither the reflector nor the re-incidence lens is arranged between the incident end and the exit end of the wavelength conversion element main body constituting the other wavelength conversion element, the entrance end and the exit end Between the signal light The incident end of the wavelength conversion element main body that constitutes the other wavelength conversion element that is at or near the condensing position that minimizes the volume of the signal light beam when viewed as the optical path length of the optical path through which the optical path passes. When the reflector and the re-incidence lens are arranged in the optical path between the light-emitting part and the light-exiting end part, the optical path of the optical path through which the signal light beam passes between the incident end part and the reaching end part immediately before the re-incident lens The wavelength conversion device is characterized by being at or near the condensing position that minimizes the volume of the signal light beam in the wavelength conversion element body when viewed as a length.

  A wavelength conversion device according to a fifth invention (hereinafter also referred to as invention 5), which is a development of the invention 4 of the present invention, is the wavelength conversion device according to the invention 4, wherein the incident light beam incident on the one wavelength conversion element is The one wavelength conversion element is configured to be incident on the one wavelength conversion element so as to be condensed at a predetermined position of the one wavelength conversion element, and the predetermined position of the one wavelength conversion element is the one wavelength conversion element The signal light beam reaching the arrival end or the signal light beam emitted from the arrival end between the incident end and the emission end of the wavelength conversion element main body constituting the element, or the vicinity thereof The reflector is arranged so that it is reflected by the reflector arranged at the same position and re-enters the same wavelength conversion element body, but a re-incident lens is arranged in the optical path between the reflector and the end of the one wavelength conversion element. Not In such a case, the light condensing position that minimizes the volume of the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between the incident end and the output end If the reflector and the re-incidence lens are not arranged between the incident end and the exit end of the wavelength conversion element body that is in the vicinity and constitutes the one wavelength conversion element, the entrance end and the exit A light converging position that minimizes the volume of the signal light beam when viewed as the optical path length of the optical path through which the signal light beam passes between the end portions, or the vicinity thereof, and constitutes the one wavelength conversion element. When the re-incident lens is disposed in the optical path between the incident end and the outgoing end of the wavelength conversion element body, the signal light beam is between the incident end and the arrival end immediately before the re-incident lens. As the optical path length of the optical path through It is a wavelength conversion device, wherein the volume of the signal light beam at a wavelength conversion element main body is condensed position or in the vicinity thereof so as to minimize the time.

  A wavelength conversion device according to a sixth invention (hereinafter also referred to as invention 6) in which the invention 4 or 5 of the present invention is developed is the wavelength conversion device according to the invention 4 or 5, wherein at least one wavelength conversion element is at least A signal light beam that passes through the re-incidence lens and re-enters the wavelength conversion element, and is collected by the re-incidence lens at a predetermined position of the wavelength conversion element. The wavelength conversion element is configured to re-enter the wavelength conversion element, and the predetermined position of the wavelength conversion element is determined by the re-incidence lens of the wavelength conversion element body constituting the wavelength conversion element and the emission of the wavelength conversion element body. Between the end portions, the signal light beam reaching the reaching end portion or the signal light beam emitted from the reaching end portion is reflected by a reflector disposed at or near the reaching end portion, and the same. When a reflector that re-enters the wavelength conversion element body is disposed, but no other re-incidence lens is disposed in the optical path between the reflector and the wavelength conversion element body. Is the optical path length of the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between the re-incidence end immediately after the re-incidence lens and the emission end of the wavelength conversion element body. A reflector is also located at or near the condensing position that minimizes the volume, and between the re-incidence lens of the wavelength conversion element body constituting the wavelength conversion element and the emission end of the wavelength conversion element body. When another re-incidence lens other than the re-incident lens is not arranged, the optical path length of the optical path through which the signal light beam passes between the re-incident end and the exit end immediately after the re-incident lens. When we saw The condensing position that minimizes the volume of the light beam or the vicinity thereof, and between the re-incidence lens of the wavelength conversion element body constituting the wavelength conversion element and the emission end of the wavelength conversion element body In the case where a reflector and another re-incidence lens other than the re-incident lens are arranged in the optical path, a re-incident end immediately after the re-incident lens and a reaching end immediately before the other re-incident lens A converging position at or near the condensing position that minimizes the volume of the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between the sections. This is a wavelength conversion device.

  A wavelength conversion device according to a seventh invention (hereinafter also referred to as invention 7) in which the inventions 1 to 6 of the present invention are developed is the wavelength conversion device according to any one of the inventions 1 to 6, wherein the incident end of the wavelength conversion element body The wavelength conversion device is characterized in that the surface to be a part and the surface on the opposite side are formed in parallel with each other with an opening angle within 1 minute.

  A wavelength conversion device according to an eighth invention (hereinafter also referred to as invention 8) in which the inventions 1 to 7 of the present invention are developed is the wavelength conversion device according to any one of the inventions 1 to 7, wherein the wavelength conversion element body is a domain-inverted region. It is a wavelength conversion device characterized by being a polarization reversal element having.

  A wavelength conversion device according to a ninth invention (hereinafter also referred to as invention 9) in which the invention 8 of the present invention is developed is the wavelength conversion device according to the invention 8, wherein the boundary between the surface of the wavelength conversion element body and the polarization inversion region The wavelength conversion device is characterized in that the surfaces are formed in parallel with each other with an opening angle within one minute.

  A wavelength conversion device according to a tenth invention (hereinafter also referred to as invention 10), in which the invention 8 or 9 of the present invention is developed, is the wavelength conversion device according to the invention 8 or 9, wherein a plurality of polarizations of the wavelength conversion element body are provided. The wavelength conversion device is characterized in that the boundary surfaces of the inversion regions are formed in parallel with each other with an opening angle within one minute.

  A wavelength conversion device according to an eleventh invention (hereinafter also referred to as invention 11) in which the inventions 8 to 10 of the present invention are developed is the wavelength conversion device according to the inventions 8 to 10, wherein the polarization inversion region of the wavelength conversion element body A width of at least 2 mm in a direction perpendicular to the optical path of incident light first incident on the wavelength conversion element body and in a plane including the optical path and the optical path of the next re-incident light It is a conversion device.

  A wavelength conversion device according to a twelfth aspect of the present invention (hereinafter also referred to as the invention twelfth) according to the eighth to eleventh aspects of the present invention is the wavelength conversion device according to any of the eighth to eleventh aspects, wherein the polarization inverting element is a PPLN (Periodically Poled). The wavelength conversion device is characterized by being LiNbO3), PPLT (Periodically Poled LiTaO3) or PPKTP (Perially Polly KTiOPO4).

  A wavelength conversion device according to a thirteenth invention (hereinafter also referred to as invention 13) in which the inventions 1 to 12 of the present invention are developed is the wavelength conversion device according to any one of inventions 1 to 12, wherein the reflector is light having a specific wavelength. A wavelength conversion device characterized in that it is a functional element that can transmit at least a part of the wavelength conversion device.

  A wavelength conversion device according to a fourteenth aspect of the present invention, which is the development of the thirteenth aspect of the present invention (hereinafter also referred to as the invention 14), is the wavelength conversion device according to the thirteenth aspect, wherein the light of the first wavelength λ1 of the reflector and The wavelength conversion device is characterized in that the reflectance with respect to one or both of the lights having the wavelength λ2 of 2 is 99.8% or more.

  A wavelength converter according to a fifteenth aspect (hereinafter also referred to as invention 15) of the inventions 8 to 14 according to the present invention is the wavelength converter according to any one of aspects 1 to 14, wherein there are a plurality of the connecting lenses. This is a characteristic wavelength converter.

  A wavelength conversion device according to a sixteenth invention (hereinafter also referred to as invention 16) in which the first to fifteenth aspects of the present invention are developed is the wavelength conversion apparatus according to the first to fifteenth aspects, wherein the connection on the optical path of the signal light beam A wavelength conversion device comprising means for changing at least one of a lens position and an angle with respect to the optical path.

  A wavelength conversion device according to a seventeenth invention (hereinafter also referred to as invention 17) in which the inventions 8 to 16 of the present invention are developed is the wavelength conversion device according to any one of the inventions 1 to 16, wherein at least two of the re-incident lenses are integrated. This is a wavelength conversion device that is configured as follows.

  A wavelength conversion device according to an eighteenth invention (hereinafter also referred to as invention 18) in which the inventions 1 to 17 of the present invention are developed is the wavelength conversion device according to the inventions 1 to 17, wherein the wavelength conversion device is arranged between two wavelength conversion elements. A wavelength converter having a plurality of connecting lenses.

  A wavelength conversion device according to a nineteenth invention (hereinafter also referred to as an invention 19) in which the inventions 1 to 18 of the present invention are developed is the wavelength conversion device according to the inventions 1 to 18, wherein at least one of the wavelength conversion devices is In the wavelength conversion optical circuit unit, the first wavelength conversion element and the second wavelength conversion element are arranged on one side of the connection lens constituting the wavelength conversion optical circuit unit, and the other side of the connection lens. A signal light optical path changing means such as a reflector capable of changing the optical path of the signal light beam traveling in the connecting lens optical path is provided on the side of the connecting lens, and at least a part of the signal light beam passing through the connecting lens is the When the optical path is changed by the signal light optical path changing means, the signal light beam emitted from one of the first wavelength conversion element and the second wavelength conversion element is the other. It is the wavelength conversion device according to claim which is folded so as to enter the wavelength conversion element. As the signal light optical path changing means, conventional optical elements such as an optical path changing prism, a corner cube, and a spread mirror can be widely used.

  A wavelength converter according to a twentieth invention (hereinafter also referred to as invention 20) as an example of the present invention is a wavelength converter using at least one wavelength converter, and an incident light beam incident on the wavelength converter is The wavelength conversion element is configured to be incident on the wavelength conversion element so as to be condensed at a predetermined position of the wavelength conversion element, and the predetermined position of the wavelength conversion element constitutes the wavelength conversion element. The signal light beam reaching the arrival end or the signal light beam emitted from the arrival end is reflected between the incident end and the emission end of the element body by a reflector disposed at or near the arrival end. The reflector that re-enters the same wavelength conversion element body is disposed, but a condensing lens (hereinafter also referred to as a re-incident lens) is disposed in the optical path between the reflector and the end of the wavelength conversion element. Have In this case, the position is equivalent to or in the vicinity of the intermediate point of the total optical path length between the incident end and the exit end, and the incident end and the exit end of the wavelength conversion element body constituting the wavelength conversion element In the case where neither the reflector nor the re-incidence lens is disposed between the portions, the wavelength conversion element is located at or near the midpoint of the total optical path length between the incident end and the exit end. In the case where the reflector and the re-incidence lens are arranged in the optical path between the incident end and the emission end of the wavelength conversion element main body, the incident end and the arrival end immediately before the re-incidence lens A wavelength conversion device characterized in that it is at or near the midpoint of the total optical path length.

  A wavelength conversion device according to a twenty-first invention (hereinafter also referred to as invention 21), in which the invention 20 of the present invention is developed, is the wavelength conversion device according to the invention 20, wherein at least one wavelength conversion element is at least one re-incidence. A signal light beam that has a lens and re-enters the wavelength conversion element through the re-incidence lens, is focused on the wavelength conversion element by the re-incidence lens at a predetermined position of the wavelength conversion element. The wavelength conversion element is configured to re-enter, and the predetermined position of the wavelength conversion element is between the re-incidence lens of the wavelength conversion element body constituting the wavelength conversion element and the emission end of the wavelength conversion element body. Then, the signal light beam reaching the reaching end or the signal light beam emitted from the reaching end is reflected by a reflector disposed at or near the reaching end to change the same wavelength. A reflector that re-enters the element main body is arranged, but when no other re-incident lens other than the re-incident lens is arranged in the optical path between the reflector and the wavelength conversion element main body, The wavelength conversion that constitutes the wavelength conversion element at or near the midpoint of the total optical path length between the re-incidence end immediately after the re-incidence lens and the output end of the wavelength conversion element body When neither a reflector nor another re-incidence lens other than the re-incidence lens is arranged between the re-incidence lens of the element main body and the emission end of the wavelength conversion element main body, the re-incidence lens and the emission The re-incident end immediately after the re-incident lens of the wavelength conversion element main body constituting the wavelength conversion element and the wavelength conversion corresponding to or near the midpoint of the total optical path length between the ends Between the output end of the element body When another re-incidence lens other than the reflector and the re-incident lens is disposed on the path, the re-incident end immediately after the re-incident lens and the reaching end immediately before the other re-incident lens A wavelength conversion device characterized in that it is at or near the midpoint of the total optical path length.

  A wavelength conversion device according to a twenty-second invention (hereinafter also referred to as invention 22) in which the invention 20 or 21 of the present invention is developed is the wavelength conversion device according to the invention 20 or 21, and is incident on the one wavelength conversion element. The incident light beam is configured to be incident on the one wavelength conversion element so as to be condensed at a predetermined position of the one wavelength conversion element, and the predetermined position of the one wavelength conversion element is A signal light beam that has reached the arrival end portion or a signal light beam that has exited from the arrival end portion is disposed between the incident end portion and the emission end portion of the wavelength conversion element body constituting one wavelength conversion element. The reflector is arranged so that it is reflected by a reflector arranged at or near the same portion and re-enters the same wavelength conversion element main body, but in the optical path between the reflector and the end of the one wavelength conversion element. When no incident lens is disposed, the volume of the signal light beam in the wavelength conversion element body is minimized when viewed as the optical path length of the optical path through which the signal light beam passes between the incident end and the exit end. When the reflector and the re-incident lens are not disposed between the incident end and the exit end of the wavelength conversion element main body constituting the one wavelength conversion element. Is the condensing position or its vicinity that minimizes the volume of the signal light beam when viewed as the optical path length of the optical path through which the signal light beam passes between the incident end and the output end, When a re-incident lens is arranged in the optical path between the incident end and the outgoing end of the wavelength conversion element main body constituting the wavelength conversion element, the incident end and the reaching end immediately before the re-incident lens The signal light between A wavelength converter which is a focusing position or in the vicinity thereof so as to minimize the volume of the signal light beam in the wavelength conversion element main body when seen in the optical path length of the optical path through which.

  A wavelength conversion device according to a twenty-third invention (hereinafter also referred to as invention 23) in which the inventions 20 to 22 of the present invention are developed is the wavelength conversion device according to the invention 20 to 22, wherein at least one wavelength conversion element is at least A signal light beam that passes through the re-incidence lens and re-enters the wavelength conversion element, and is collected by the re-incidence lens at a predetermined position of the wavelength conversion element. The wavelength conversion element is configured to re-enter the wavelength conversion element, and the predetermined position of the wavelength conversion element is determined by the re-incidence lens of the wavelength conversion element body constituting the wavelength conversion element and the emission of the wavelength conversion element body. Between the end portions, the signal light beam reaching the reaching end portion or the signal light beam emitted from the reaching end portion is reflected by a reflector disposed at or near the reaching end portion. When a reflector that re-enters the same wavelength conversion element body is disposed, but no other re-incidence lens is disposed in the optical path between the reflector and the wavelength conversion element body. The signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between the re-incidence end immediately after the re-incidence lens and the emission end of the wavelength conversion element body A reflector between the re-incidence lens of the wavelength conversion element main body and the output end of the wavelength conversion element main body, which is at or near the condensing position that minimizes the volume of the wavelength conversion element If no other re-incidence lens is arranged other than the re-incidence lens, the optical path length of the optical path through which the signal light beam passes between the re-incident end and the exit end immediately after the re-incident lens As seen The condensing position that minimizes the volume of the signal light beam or the vicinity thereof, the re-incidence lens of the wavelength conversion element body constituting the wavelength conversion element, and the exit end of the wavelength conversion element body In the case where a reflector and another re-incident lens other than the re-incident lens are arranged in the optical path between them, the re-incident end immediately after the re-incident lens and the arrival before the other re-incident lens A condensing position at or near the condensing position that minimizes the volume of the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between the ends. Is a wavelength conversion device.

  A wavelength conversion device according to a twenty-fourth invention (hereinafter also referred to as invention 24) in which the inventions 20 to 23 of the present invention are developed is the wavelength conversion device according to any one of the inventions 20 to 23, wherein the incident end of the wavelength conversion element main body is the same. The wavelength conversion device is characterized in that the surface to be a part and the surface on the opposite side are formed in parallel with each other with an opening angle within 1 minute.

  A wavelength conversion device according to a twenty-fifth invention (hereinafter also referred to as invention 25) in which the inventions 20 to 24 of the present invention are developed is the wavelength conversion device according to any one of the inventions 20 to 24, wherein the wavelength conversion element body is a domain-inverted region. It is a wavelength conversion device characterized by being a polarization reversal element having.

  A wavelength conversion device according to a twenty-sixth invention (hereinafter also referred to as invention 26) in which the invention 25 of the present invention is developed is the wavelength conversion device according to the invention 25, wherein the boundary between the surface of the wavelength conversion element body and the polarization inversion region. The wavelength conversion device is characterized in that the surfaces are formed in parallel with each other with an opening angle within one minute.

  A wavelength conversion device according to a twenty-seventh invention (hereinafter also referred to as invention 27), in which the invention 25 or 26 of the present invention is developed, is the wavelength conversion device according to the invention 25 or 26, wherein a plurality of polarizations of the wavelength conversion element body are provided. The wavelength conversion device is characterized in that the boundary surfaces of the inversion regions are formed in parallel with each other with an opening angle within one minute.

  A wavelength conversion device according to a twenty-eighth invention (hereinafter also referred to as invention 28) in which the inventions 25 to 27 of the present invention are developed is the wavelength conversion device according to the invention 25 to 27, wherein the polarization inversion region of the wavelength conversion element body is A width of at least 2 mm in a direction perpendicular to the optical path of incident light first incident on the wavelength conversion element body and in a plane including the optical path and the optical path of the next re-incident light It is a conversion device.

  A wavelength conversion device according to a twenty-ninth invention (hereinafter also referred to as invention 29), which is the development of the inventions 25 to 28 of the present invention, is the wavelength conversion device according to the invention 25 to 28, wherein the polarization inverting element is a PPLN (Periodically Poled). The wavelength conversion device is characterized by being LiNbO3), PPLT (Periodically Poled LiTaO3) or PPKTP (Perially Polly KTiOPO4).

  A wavelength conversion device according to a thirtieth invention (hereinafter also referred to as invention 30) in which the inventions 20 to 29 of the present invention are developed, the wavelength conversion device according to any one of inventions 20 to 29, wherein the reflector is The wavelength conversion device is a functional element capable of transmitting at least part of light of a specific wavelength.

  A wavelength conversion device according to a thirty-first invention (hereinafter also referred to as invention 31), in which the invention 30 of the present invention is developed, is the wavelength conversion device according to the invention 30, wherein the light having the first wavelength λ1 of the reflector and the wavelength conversion device are the same. The wavelength conversion device is characterized in that the reflectance with respect to one or both of the lights having the wavelength λ2 of 2 is 99.8% or more.

  A wavelength conversion device according to a thirty-second invention (hereinafter also referred to as invention 32) in which the inventions 20 to 31 of the present invention are developed is the wavelength conversion device according to the inventions 20 to 31, wherein at least two of the re-incident lenses are integrated. This is a wavelength conversion device that is configured as follows.

  A wavelength converter according to a thirty-third invention (hereinafter also referred to as invention 33) in which the inventions 20 to 32 of the present invention are developed is the wavelength converter according to the invention 20 to 32, wherein the connection on the optical path of the signal light beam A wavelength conversion device comprising means for changing at least one of a lens position and an angle with respect to the optical path.

  A wavelength converter according to a thirty-fourth invention (hereinafter also referred to as invention 34) as an example of the present invention is a wavelength converter using at least two wavelength conversion elements, and the wavelength converter is a signal subjected to wavelength conversion. At least one wavelength conversion optical circuit unit having at least two wavelength conversion elements connected in series via a lens (hereinafter also referred to as a connection lens) in the optical path of the light beam; At least one of the wavelength conversion optical circuit units emits one of the two wavelength conversion elements connected in series via the connection lens (hereinafter also referred to as a first wavelength conversion element). The optical path of the signal light beam including the optical path passing through the connection lens between the end and the incident end of the other wavelength conversion element (hereinafter also referred to as the second wavelength conversion element) is also referred to as a connection lens optical path. Then, the signal light beam emitted from the first wavelength conversion element passes through the connection lens optical path and is condensed at a predetermined position of the second wavelength conversion element by the connection lens. It is comprised so that it may inject into a wavelength conversion element, The said predetermined position of a said 2nd wavelength conversion element is the incident end part and output end part of the wavelength conversion element main body which comprises the said 2nd wavelength conversion element During this period, the signal light beam that has reached the reaching end portion or the signal light beam that has exited from the reaching end portion is reflected by a reflector disposed at or near the reaching end portion, and is incident again on the same wavelength conversion element main body. The incident end when the reflector is disposed but a condensing lens (hereinafter also referred to as a re-incident lens) is not disposed in the optical path between the reflector and the end of the second wavelength conversion element. Between the head and the output end The second wavelength conversion element is configured at or near the condensing position that minimizes the volume of the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes. The optical path through which the signal light beam passes between the incident end and the exit end when neither the reflector nor the re-incidence lens is disposed between the incident end and the exit end of the wavelength conversion element body. The wavelength conversion element body constituting the second wavelength conversion element at or near the condensing position that minimizes the volume of the signal light beam in the wavelength conversion element body when viewed as the optical path length When a re-incident lens is disposed in the optical path between the incident end and the outgoing end of the optical path, the optical path of the optical path through which the signal light beam passes between the incident end and the arrival end immediately before the re-incident lens As long as The wavelength conversion device is characterized by being at or near the condensing position that minimizes the volume of the signal light beam in the wavelength conversion element body.

  A wavelength conversion device according to a thirty-fifth aspect of the present invention (hereinafter also referred to as the thirty-fifth aspect), in which the thirty-fourth aspect of the present invention is developed, is the wavelength conversion device according to the thirty-fourth aspect, wherein the incident light beam is incident on the first wavelength conversion element. Is configured to be incident on the one wavelength conversion element so as to be condensed at a predetermined position of the one wavelength conversion element, and the predetermined position of the one wavelength conversion element is the one wavelength A signal light beam reaching the arrival end or a signal light beam emitted from the arrival end between the incident end and the emission end of the wavelength conversion element body constituting the conversion element is the arrival end or its end The reflector that is reflected by a reflector disposed in the vicinity and re-enters the same wavelength conversion element main body is disposed, but a re-incident lens is disposed in the optical path between the reflector and the end of the one wavelength conversion element. Arranged If not, the condensing position that minimizes the volume of the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between the incident end and the output end Alternatively, if the reflector and the re-incidence lens are not disposed between the incident end and the emission end of the wavelength conversion element main body constituting the one wavelength conversion element, the incident end The light converging position or the vicinity thereof that minimizes the volume of the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between When a re-incident lens is disposed in the optical path between the incident end and the outgoing end of the wavelength conversion element main body constituting the wavelength conversion element, the incident end and the arrival end immediately before the re-incidence lens The signal between parts Is a wavelength conversion device, characterized in that the volume of the signal light beam in the wavelength conversion element main body is condensed position or in the vicinity thereof so as to minimize when viewed as a optical path length of the optical path which the beam passes.

  A wavelength converter according to a thirty-sixth aspect of the present invention (hereinafter also referred to as the thirty-sixth aspect) according to the thirty-fourth aspect of the present invention is the wavelength converter according to the thirty-fourth aspect of the present invention, wherein at least one wavelength conversion element is at least A signal light beam that passes through the re-incidence lens and re-enters the wavelength conversion element, and is collected by the re-incidence lens at a predetermined position of the wavelength conversion element. The wavelength conversion element is configured to re-enter the wavelength conversion element, and the predetermined position of the wavelength conversion element is the re-incidence lens of the wavelength conversion element body constituting the wavelength conversion element and the emission of the wavelength conversion element body. A reflector in which the signal light beam reaching the reaching end portion or the signal light beam emitted from the reaching end portion is arranged between the end portions or in the vicinity thereof. A reflector that is incident on the same wavelength conversion element main body is disposed, but another re-incidence lens is disposed on the optical path between the reflector and the wavelength conversion element main body. If not, the wavelength conversion element body in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between the re-incidence end part immediately after the re-incidence lens and the emission end part of the wavelength conversion element body A condensing position that minimizes the volume of the signal light beam or its vicinity, and between the re-incident lens of the wavelength conversion element body constituting the wavelength conversion element and the emission end of the wavelength conversion element body In the case where neither the reflector nor another re-incidence lens other than the re-incident lens is arranged, the optical path through which the signal light beam passes between the re-incident end and the exit end immediately after the re-incident lens As the optical path length of The re-incident lens and the wavelength of the wavelength conversion element body constituting the wavelength conversion element at or near the condensing position that minimizes the volume of the signal light beam in the wavelength conversion element body When another re-incidence lens other than the reflector and the re-incidence lens is arranged in the optical path between the output end of the conversion element body, the re-incidence end immediately after the re-incidence lens and the other A condensing position that minimizes the volume of the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between the arrival ends immediately before the re-incidence lens Alternatively, it is a wavelength converter characterized by being in the vicinity thereof.

  A wavelength conversion device according to a thirty-seventh invention (hereinafter also referred to as invention 37), in which the inventions 34 to 36 of the present invention are developed, is the wavelength conversion device according to the inventions 34 to 36, wherein the incident end of the wavelength conversion element main body. The wavelength conversion device is characterized in that the surface to be a part and the surface on the opposite side are formed in parallel with each other with an opening angle within 1 minute.

  A wavelength converter according to a thirty-eighth aspect (hereinafter also referred to as invention 38) of the present inventions 34 to 37 according to the present invention is the wavelength converter according to any of the thirty-fourth to thirty-seventh aspects, wherein the wavelength conversion element body is a domain-inverted region. It is a wavelength conversion device characterized by being a polarization reversal element having.

  A wavelength converter according to a thirty-ninth aspect of the present invention (hereinafter also referred to as the thirty-ninth aspect) is a wavelength conversion apparatus according to the thirty-eighth aspect, wherein the boundary between the surface of the wavelength conversion element body and the domain-inverted region is provided. The wavelength conversion device is characterized in that the surfaces are formed in parallel with each other with an opening angle within one minute.

  A wavelength conversion device according to a 40th aspect (hereinafter also referred to as invention 40) of the invention 38 or 39 according to the invention is the wavelength conversion device according to aspect 38 or 39, wherein a plurality of polarizations of the wavelength conversion element body are provided. The wavelength conversion device is characterized in that the boundary surfaces of the inversion regions are formed in parallel with each other with an opening angle within one minute.

  A wavelength conversion device according to a forty-first invention (hereinafter also referred to as invention 41) in which the inventions 38 to 40 of the present invention are developed is the wavelength conversion device according to the invention 38 to 40, wherein the polarization inversion region of the wavelength conversion element body is A width of at least 2 mm in a direction perpendicular to the optical path of incident light first incident on the wavelength conversion element body and in a plane including the optical path and the optical path of the next re-incident light It is a conversion device.

  A wavelength converter according to a forty-second invention (hereinafter also referred to as invention 42) in which the inventions 38 to 41 of the present invention are developed is the wavelength converter according to the invention 38 to 41, wherein the polarization inverting element is PPLN (Periodically Poled). The wavelength conversion device is characterized by being LiNbO3), PPLT (Periodically Poled LiTaO3) or PPKTP (Perially Polly KTiOPO4).

  A wavelength conversion device according to a forty-third invention (hereinafter also referred to as invention 43) in which the inventions 34 to 42 of the present invention are developed is the wavelength conversion device according to any of the inventions 34 to 42, wherein the reflector is light having a specific wavelength. A wavelength conversion device characterized in that it is a functional element that can transmit at least a part of the wavelength conversion device.

  A wavelength conversion device according to a forty-fourth invention (hereinafter also referred to as invention 44), which is a development of the invention 43 of the present invention, is the wavelength conversion device according to the invention 43, wherein the light of the first wavelength λ1 of the reflector and the wavelength conversion device are the same. The wavelength conversion device is characterized in that the reflectance with respect to one or both of the lights having the wavelength λ2 of 2 is 99.8% or more.

  A wavelength converter according to a forty-fifth aspect (hereinafter also referred to as "invention 45") of the inventions 34 to 44 according to the present invention is the wavelength converter according to the invention 34 to 44, wherein at least two of the re-incident lenses are integrated. This is a wavelength conversion device that is configured as follows.

  A wavelength converter according to a forty-sixth invention (hereinafter also referred to as invention 46), in which the inventions 34 to 45 of the present invention are developed, is the wavelength converter according to the invention 34 to 45, wherein the wavelength converter is provided between two wavelength conversion elements. A wavelength converter having a plurality of connecting lenses.

  A wavelength converter according to a forty-seventh aspect (hereinafter also referred to as invention 47) of the inventions 34 to 46 according to the present invention is the wavelength converter according to any one of aspects 34 to 46, wherein the connection on the optical path of the signal light beam. A wavelength conversion device comprising means for changing at least one of a lens position and an angle with respect to the optical path.

  A wavelength conversion device according to a forty-eighth invention (hereinafter also referred to as invention 48), in which the inventions 34 to 47 of the present invention are developed, is the wavelength conversion device according to the invention 34 to 47, in which at least one of the wavelength conversion devices is In the wavelength conversion optical circuit unit, the first wavelength conversion element and the second wavelength conversion element are arranged on one side of the connection lens constituting the wavelength conversion optical circuit unit, and the other side of the connection lens. A signal light optical path changing means such as a reflector capable of changing the optical path of the signal light beam traveling in the connecting lens optical path is provided on the side of the connecting lens, and at least a part of the signal light beam passing through the connecting lens is the A signal light beam whose optical path is folded by the signal light optical path changing means and whose optical path is emitted from one of the first wavelength conversion element and the second wavelength conversion element. It is the wavelength conversion device according to claim which is folded so as to enter the other of the wavelength conversion element.

  A wavelength conversion device according to a 49th invention (hereinafter also referred to as invention 49) as an example of the present invention is a wavelength conversion device using at least one wavelength conversion element, and an incident light beam incident on the wavelength conversion element is: The wavelength conversion element is configured to be incident on the wavelength conversion element so as to be condensed at a predetermined position of the wavelength conversion element, and the predetermined position of the wavelength conversion element constitutes the wavelength conversion element The signal light beam reaching the arrival end or the signal light beam emitted from the arrival end is reflected between the incident end and the emission end of the main body by a reflector disposed at or near the arrival end. The reflector that re-enters the same wavelength conversion element body is disposed, but a condenser lens (hereinafter also referred to as a re-incidence lens) is disposed in the optical path between the reflector and the end of the wavelength conversion element. Na In such a case, the light condensing position that minimizes the volume of the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between the incident end and the output end When the reflector and the re-incidence lens are not disposed between the incident end and the exit end of the wavelength conversion element main body that is in the vicinity and constitutes the wavelength conversion element, the entrance end and the exit end The wavelength conversion element is at or near the condensing position that minimizes the volume of the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes. When a re-incident lens is disposed in the optical path between the incident end and the outgoing end of the wavelength conversion element body, the signal is between the incident end and the arrival end immediately before the re-incident lens. Of the light path through which the light beam passes A wavelength converter which is a focusing position or in the vicinity thereof so as to minimize the volume of the signal light beam in the wavelength conversion element main body when viewed as a path length.

  A wavelength conversion device according to a 50th aspect (hereinafter also referred to as invention 50) of the present invention 49, which is the development of the present invention 49, is the wavelength conversion device according to aspect 49, wherein at least one wavelength conversion element is at least one re-incidence. A signal light beam that has a lens and re-enters the wavelength conversion element through the re-incidence lens, is focused on the wavelength conversion element by the re-incidence lens at a predetermined position of the wavelength conversion element. The wavelength conversion element is configured to re-enter, and the predetermined position of the wavelength conversion element is between the re-incidence lens of the wavelength conversion element body constituting the wavelength conversion element and the emission end of the wavelength conversion element body. Then, the signal light beam reaching the reaching end or the signal light beam emitted from the reaching end is reflected by a reflector disposed at or near the reaching end to change the same wavelength. In the case where a reflector that re-enters the element body is disposed, but no other re-incident lens other than the re-incident lens is disposed in the optical path between the reflector and the wavelength conversion element body, the incident end A condensing position or the vicinity thereof that minimizes the volume of the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between the light emitting portion and the emission end, Between the re-incident end immediately after the re-incidence lens of the wavelength conversion element main body constituting the wavelength conversion element and the output end of the wavelength conversion element main body, the reflector is another re-entrance different from the re-incident lens. When the incident lens is not arranged, the signal in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between the re-incidence end and the exit end immediately after the re-incidence lens The volume of the light beam It is a condensing position to make it small or its vicinity, and a reflector is provided in the optical path between the re-incidence lens of the wavelength conversion element body constituting the wavelength conversion element and the emission end of the wavelength conversion element body. When another re-incidence lens other than the re-incident lens is arranged, the signal between the re-incident end immediately after the re-incident lens and the reaching end immediately before the other re-incident lens. A wavelength conversion device characterized by being at or near a condensing position that minimizes the volume of the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the light beam passes .

  A wavelength conversion device according to a fifty-first invention (hereinafter also referred to as invention 51) in which the invention 49 or 50 of the present invention is developed is the wavelength conversion device according to the invention 49 or 50, in which the incident end of the wavelength conversion element body is the incident end. The wavelength conversion device is characterized in that the surface to be a part and the surface on the opposite side are formed in parallel with each other with an opening angle within 1 minute.

  A wavelength converter according to a fifty-second invention (hereinafter also referred to as invention 52), in which the inventions 49 to 51 of the present invention are developed, is the wavelength converter according to any of the inventions 49 to 51, wherein the wavelength conversion element body is The wavelength conversion device is a polarization reversal element having a polarization reversal region.

  A wavelength converter according to a fifty-third invention (hereinafter also referred to as invention 53) in which the invention 52 of the present invention is developed is the wavelength converter according to the invention 52, wherein the boundary between the surface of the wavelength conversion element body and the domain-inverted region. The wavelength conversion device is characterized in that the surfaces are formed in parallel with each other with an opening angle within one minute.

  A wavelength converter according to a fifty-fourth invention (hereinafter also referred to as invention 54) obtained by developing the invention 52 or 53 according to the present invention is the wavelength converter according to the invention 52 or 53, wherein a plurality of polarizations of the wavelength conversion element body are provided. The wavelength conversion device is characterized in that the boundary surfaces of the inversion regions are formed in parallel with each other with an opening angle within one minute.

  A wavelength converter according to a fifty-fifth invention (hereinafter also referred to as invention 55) obtained by developing the inventions 52 to 54 of the present invention is the wavelength converter according to the invention 52 to 54, wherein the domain-inverted region of the wavelength converter element body is the same. A width of at least 2 mm in a direction perpendicular to the optical path of incident light first incident on the wavelength conversion element body and in a plane including the optical path and the optical path of the next re-incident light It is a conversion device.

  A wavelength converter according to a fifty-sixth invention (hereinafter also referred to as invention 56) in which the inventions 52 to 55 of the present invention are developed, in the wavelength converter according to the invention 52 to 55, the polarization inversion element is PPLN (Periodically Poled). The wavelength conversion device is characterized by being LiNbO3), PPLT (Periodically Poled LiTaO3) or PPKTP (Perially Polly KTiOPO4).

  A wavelength converter according to a 57th aspect (hereinafter also referred to as invention 57) of the inventions 49 to 56 according to the present invention is the wavelength converter according to aspects 49 to 56, wherein at least two of the re-incident lenses are integrated. This is a wavelength conversion device that is configured as follows.

  A wavelength converter according to a 58th invention (hereinafter also referred to as invention 58), in which the inventions 49 to 57 of the present invention are developed, is the wavelength converter according to the invention 49 to 57, wherein the connection on the optical path of the signal light beam A wavelength conversion device comprising means for changing at least one of a lens position and an angle with respect to the optical path.

  A wavelength conversion method according to a 59th invention (hereinafter also referred to as invention 59) as an example of the present invention is a wavelength conversion method for converting the wavelength of signal light by using at least two wavelength conversion elements, and the wavelength conversion method includes: , Using at least two wavelength conversion elements connected in series via a lens (hereinafter also referred to as a connection lens) in the optical path of the signal light beam subjected to wavelength conversion, and connected in series via the connection lens The output end of one of the two wavelength conversion elements connected (hereinafter also referred to as a first wavelength conversion element) and the other wavelength conversion element (hereinafter also referred to as a second wavelength conversion element). The optical path of the signal light beam including the optical path passing through the connecting lens between the incident end portions is also referred to as a connecting lens optical path, and one of the connecting lens optical paths is sandwiched between the intermediate points of the connecting lens optical paths. The first wavelength conversion element is disposed on the side of the connection lens, the second wavelength conversion element is disposed on the other side of the connection lens optical path, and the signal light beam emitted from the first wavelength conversion element is The second wavelength conversion element is configured to be incident on the second wavelength conversion element so as to pass through a connection lens and be condensed at a predetermined position of the second wavelength conversion element by the connection lens. The signal light beam that has reached the arrival end or the signal light that has exited from the arrival end between the incident end and the emission end of the wavelength conversion element main body constituting the second wavelength conversion element The reflector for reflecting the beam by the reflector disposed at or near the reaching end and re-entering the same wavelength conversion element main body is disposed, but the end of the reflector and the second wavelength conversion element is disposed. Condensing lens in the optical path between If the re-incidence lens is not arranged, the wavelength of the signal light is converted so that it is at or near the midpoint of the total optical path length between the incident end and the exit end. In the case where neither the reflector nor the re-incidence lens is arranged between the incident end and the exit end of the wavelength conversion element main body constituting the second wavelength conversion element, the entrance end and the exit end The wavelength conversion element body constituting the second wavelength conversion element by converting the wavelength of the signal light so as to be at or near the position corresponding to the intermediate point of the total optical path length between the sections When the reflector and the re-incidence lens are arranged in the optical path between the incident end and the exit end, it corresponds to the intermediate point of the total optical path length between the entrance end and the arrival end immediately before the re-incidence lens. Convert the wavelength of signal light so that it is at or near the position The wavelength conversion method characterized by the above.

  A wavelength conversion method according to a sixty-second invention (hereinafter also referred to as the invention 60) in which the invention 59 of the present invention is developed is the wavelength conversion method according to the invention 59, wherein at least one wavelength conversion element has at least one re-incidence. A signal light beam that has a lens and re-enters the wavelength conversion element through the re-incidence lens, is focused on the wavelength conversion element by the re-incidence lens at a predetermined position of the wavelength conversion element. The wavelength conversion element is configured to re-enter, and the predetermined position of the wavelength conversion element is between the re-incidence lens of the wavelength conversion element main body and the emission end of the wavelength conversion element main body constituting the wavelength conversion element. Then, the signal light beam reaching the reaching end or the signal light beam emitted from the reaching end is reflected by a reflector disposed at or near the reaching end to change the same wavelength. A reflector that re-enters the element main body is arranged, but when no other re-incident lens other than the re-incident lens is arranged in the optical path between the reflector and the wavelength conversion element main body, Convert the wavelength of the signal light so that it is at or near the midpoint of the total optical path length between the re-incidence end immediately after the re-incidence lens and the output end of the wavelength conversion element body, Between the re-incident lens of the wavelength conversion element main body constituting the wavelength conversion element and the exit end of the wavelength conversion element main body, a reflector and another re-incident lens other than the re-incident lens are also arranged. If not, convert the wavelength of the signal light so that it is at or near the midpoint of the total optical path length between the re-incidence end and the exit end immediately after the re-incidence lens. Wavelength conversion element constituting conversion element When another re-incidence lens other than the reflector and the re-incidence lens is arranged in the optical path between the re-incidence lens of the body and the exit end of the wavelength conversion element main body, The wavelength of the signal light is converted so that it is at or near the position corresponding to the midpoint of the total optical path length between the re-incidence end immediately after and the arrival end just before the other re-incidence lens. This is a wavelength conversion method.

  A wavelength conversion method according to a 61st invention (hereinafter also referred to as invention 61) obtained by developing the invention 59 or 60 of the present invention is the wavelength conversion method according to the invention 59 or 60, wherein a polarization inversion region is provided in the wavelength conversion element body. A wavelength conversion method characterized by using a polarization inversion element having

  A wavelength conversion method according to a 62nd invention (hereinafter also referred to as invention 62) as an example of the present invention is a wavelength conversion method that converts the wavelength of signal light using at least two wavelength conversion elements, and the wavelength conversion method is , Using at least two wavelength conversion elements connected in series via a lens (hereinafter also referred to as a connection lens) in the optical path of the signal light beam subjected to wavelength conversion, and connected in series via the connection lens The output end of one of the two wavelength conversion elements connected (hereinafter also referred to as a first wavelength conversion element) and the other wavelength conversion element (hereinafter also referred to as a second wavelength conversion element). The optical path of the signal light beam including the optical path passing through the connecting lens between the incident end portions is also referred to as a connecting lens optical path, and one of the connecting lens optical paths is sandwiched between the intermediate points of the connecting lens optical paths. The first wavelength conversion element is disposed on the side of the connection lens, the second wavelength conversion element is disposed on the other side of the connection lens optical path, and the signal light beam emitted from the first wavelength conversion element is The light is incident on the second wavelength conversion element so as to be condensed at a predetermined position of the second wavelength conversion element by the connection lens through the connection lens, and the predetermined position of the second wavelength conversion element is The signal light beam reaching the arrival end or the signal light beam emitted from the arrival end is reached between the incident end and the emission end of the wavelength conversion element main body constituting the second wavelength conversion element. An optical path between the reflector and the end of the second wavelength conversion element is disposed where the reflector that is reflected by the reflector disposed at or near the end and re-enters the same wavelength conversion element main body is disposed. Condensing lens (hereinafter re-entry) If the lens is not disposed, the volume of the signal light beam in the wavelength conversion element body is minimized when viewed as the optical path length of the optical path through which the signal light beam passes between the incident end and the output end. The wavelength of the signal light is converted so as to be at or near the condensing position, and between the incident end and the output end of the wavelength conversion element body constituting the second wavelength conversion element When neither the reflector nor the re-incidence lens is arranged, the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between the incident end and the exit end. The wavelength conversion element main body constituting the second wavelength conversion element converts the wavelength of the signal light so as to be at or near the condensing position that minimizes the volume, and enters and exits the wavelength conversion element body. Re-incident level in the optical path between The signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between the incident end and the arrival end immediately before the re-incidence lens. The wavelength conversion method is characterized in that the wavelength of the signal light is converted so as to be at or near the condensing position where the volume of the light is minimized.

  A wavelength conversion method according to a 63rd invention (hereinafter also referred to as an invention 63) in which the invention 62 of the present invention is developed is the wavelength conversion method according to the invention 62, wherein at least one wavelength conversion element is at least one re-incident. A signal light beam that has a lens and re-enters the wavelength conversion element through the re-incidence lens, is focused on the wavelength conversion element by the re-incidence lens at a predetermined position of the wavelength conversion element. The wavelength conversion element is configured to re-enter, and the predetermined position of the wavelength conversion element is between the re-incidence lens of the wavelength conversion element main body and the emission end of the wavelength conversion element main body constituting the wavelength conversion element. Then, the signal light beam reaching the reaching end or the signal light beam emitted from the reaching end is reflected by a reflector disposed at or near the reaching end to change the same wavelength. A reflector that re-enters the element main body is arranged, but when no other re-incident lens other than the re-incident lens is arranged in the optical path between the reflector and the wavelength conversion element main body, The volume of the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between the re-incidence end immediately after the re-incidence lens and the emission end of the wavelength conversion element body The wavelength of the signal light is converted so as to be at or near the condensing position to be minimized, and the re-incident lens of the wavelength conversion element body constituting the wavelength conversion element and the emission of the wavelength conversion element body When neither a reflector nor another re-incidence lens other than the re-incidence lens is disposed between the end portions, the signal light is transmitted between the re-incidence end portion immediately after the re-incident lens and the emission end portion. The optical path of the optical path through which the beam passes The wavelength conversion element is configured to convert the wavelength of the signal light so that the volume of the signal light beam in the wavelength conversion element body is minimized or at the vicinity of the condensing position. When another re-incidence lens other than the reflector and the re-incident lens is arranged in the optical path between the re-incident lens of the wavelength conversion element main body and the emission end of the wavelength conversion element main body, The signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between the re-incidence end immediately after the incident lens and the arrival end immediately before the other re-incidence lens The wavelength conversion method is characterized in that the wavelength of the signal light is converted so as to be at or near the condensing position that minimizes the volume of the optical system.

  A wavelength conversion method according to a sixty-fourth invention (hereinafter also referred to as invention 64) obtained by developing the invention 62 or 63 of the present invention is the wavelength conversion method according to the invention 62 or 63, wherein the polarization inversion region is provided in the wavelength conversion element body. It is a wavelength conversion method characterized by being a polarization reversal element having.

  In the 65th invention as an example of the present invention (hereinafter also referred to as the invention 65), the light having the first wavelength λ1 included in the incident light is converted into the second wavelength λ2 having a wavelength different from the first wavelength λ1. The element itself that can convert the wavelength of the light into the wavelength conversion element is referred to as the wavelength conversion element, and the end of the wavelength conversion element that makes the incident light incident on the wavelength conversion element is defined as the incident end, and the incident light becomes the wavelength conversion element. The light enters the wavelength conversion element and undergoes wavelength conversion from the light of the first wavelength λ1 to the light of the second wavelength λ2, and travels the light of the first wavelength λ1 and the light of the second wavelength λ2. An end portion that is different from the incident end portion of the wavelength conversion element that reaches as contained light or the vicinity of the end portion is defined as a reaching end portion of the wavelength conversion element, and the wavelength conversion is performed in the reaching end portion. The end which takes out the received light as outgoing light or the end The vicinity is defined as the output end of the wavelength conversion element, and the incident light including the light having the first wavelength λ1 before being incident on the wavelength conversion element and the incident light are incident on the wavelength conversion element and subjected to wavelength conversion. The incident light including the light of the first wavelength λ1 and the light of the second wavelength λ2 traveling in the wavelength conversion element and the incident light incident on the wavelength conversion element travel in the wavelength conversion element and perform wavelength conversion. Each of the emitted light emitted from the wavelength conversion element or collectively referred to as signal light, and the wavelength conversion element of the invention 65 has at least one arrival end portion different from the incident end portion and the emission end portion. And at least the light having the first wavelength λ1 as the signal light reaching the reflection end portion or the vicinity thereof is reflected to the light having the second wavelength λ2 in the wavelength conversion element. To proceed while undergoing wavelength conversion The wavelength conversion element is a polarization reversal element having a polarization reversal region, and condition 1 is 1 minute between the incident surface of the wavelength conversion element and the boundary surface of the polarization reversal region. The condition 2 is that the output surface of the wavelength conversion element and the boundary surface of the domain-inverted region are formed parallel to each other with an opening angle of less than 1 minute. And condition 3 is that the boundary surfaces of the plurality of domain-inverted regions are formed in parallel with each other with an opening angle within 1 minute, and condition 4 is that the width of the domain-inverted region is the wavelength conversion It is assumed that there is at least 2 mm in the width in the plane perpendicular to the optical path of the incident light first incident on the element and including the optical path and the optical path of the next re-incident light, and Condition 5 is the incident end of the wavelength conversion element. Part surface and it The wavelength, wherein the wavelength conversion element satisfies at least two of the above conditions 1 to 5 by being formed in parallel with each other at an opening angle of less than 1 minute with the opposite surface It is a conversion element.

  In the above, examples of the present invention have been described as means for solving the problems. However, the present invention is not limited to these, and many variations are possible. It is obvious that the present invention can be configured, and as described later, the basic technology of the present invention can be developed to configure many inventions.

  As described above, the wavelength conversion method and the wavelength conversion apparatus according to the present invention can make incident light incident so that the wavelength can be converted effectively, and can further increase the wavelength conversion efficiency. Therefore, it is possible to provide a wavelength conversion element and a wavelength conversion device that are small in size, have high wavelength conversion efficiency, and have high output at low cost, and that a coherent light source using them can be provided at low cost. There is an effect.

  Embodiments of the present invention will be described below with reference to the drawings. The drawings used for the description schematically show the dimensions, shapes, arrangement relationships, and the like of each component to the extent that an example of the present invention can be understood. For convenience of explanation of the present invention, there may be cases where the enlargement ratio is partially changed for illustration, and the drawings used for explanation of the examples of the present invention may not necessarily be similar to the actual objects and descriptions of the embodiments. Moreover, in each figure, about the same component, it attaches and shows the same number, The overlapping description may be abbreviate | omitted.

  As mentioned above, the remarkable feature of the basic idea of the technology used in the present invention is that the condensing optical system when the signal light to be subjected to wavelength conversion is made incident on the wavelength conversion element is conventionally used for the wavelength conversion element. In the present invention, the incident light to the wavelength conversion element by the condensing optical system is used in the present invention as described in the following. The method of condensing light is managed in a particularly preferable state so that high-quality, high-output wavelength-converted light can be obtained with high wavelength conversion efficiency. Furthermore, in the present invention, the qualitative improvement of the wavelength conversion in the wavelength conversion element body is aimed at, and the wavelength conversion element body is markedly improved.

  The exemplary embodiment of the present invention has several features. The present invention can be implemented as a wavelength conversion method and a wavelength conversion device that pay attention to each of the respective characteristics, and can also be implemented by combining several characteristics.

  In addition, the explanation of the technical idea of the wavelength conversion device and the wavelength conversion method of the present invention can be easily understood from the following explanation. Therefore, in order to avoid duplication, the explanation of the wavelength conversion method of the present invention is also used as the explanation of the wavelength conversion method of the present invention, or the technical idea of the wavelength conversion method of the present invention is used in the range where no major omission occurs and no misunderstanding occurs. The description of the wavelength conversion method may also serve as an explanation of the technical idea of the wavelength conversion device of the present invention.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  Before explaining the configuration of the present invention, the wavelength conversion element constituting the present invention and wavelength conversion using the same will be described.

  FIG. 1 and FIG. 2 are diagrams for explaining examples of the wavelength conversion element of the present invention, which are explained using a cross section including an optical path of light subjected to wavelength conversion. FIG. 1 is a diagram showing a domain-inverted region (not shown) shown below, and FIG. 2 is a diagram showing examples of domain-inverted regions.

  1 and 2, reference numeral 20a denotes a wavelength conversion element, 21 denotes an incident light beam (incident light) incident on the wavelength conversion element 20a with coherent light having a wavelength λ1 from a laser light source (not shown). 22 is a polarization inversion nonlinear wavelength conversion element body as a wavelength conversion element body constituting the wavelength conversion element 20a, 33 is a polarization inversion region of the wavelength conversion element body 22, 71a to 71c are optical paths, and 11a is a wavelength. The incident end portions 12a to 12c at which the incident light beam 21 is incident on the conversion element main body 22 are incident on the wavelength conversion element main body 22. The advancing end portion 13a that has reached the end portion (surface) of the wavelength conversion element main body while undergoing wavelength conversion in the wavelength conversion element main body, and 13a converts the wavelength of the optical path 71c. An exit end 711 from which the signal light traveling while being received exits, 711 indicates a position corresponding to an intermediate point (also referred to as a central point) of all the optical path lengths of the optical paths 71a to 71c from the entrance end 11a to the exit end 13a. Reference numerals 23 and 26 are antireflection films, 24 and 25 are reflection films as reflectors, and 27 is an outgoing light beam.

  As the antireflection films 23 and 26, an antireflection film used in a conventional optical element can be used.

  As the reflection films 24 and 25, a multilayer film having reflection characteristics in which the reflectance for light having a wavelength of λ1 and the reflectance for light having a wavelength of λ2 are both 90% or more can be used. The reflectance is particularly preferably 99% or more, particularly 99.8% or more, and a particularly preferable effect can be exhibited by using a multilayer film having a reflectance of 99.9% or more.

  In FIG. 1 and FIG. 2, the incident light, that is, the signal light beam incident on the wavelength conversion element body 22 from the incident end 11a undergoes wavelength conversion from the first wavelength λ1 to the second wavelength λ2 in the polarization inversion region 33. The light travels while reaching the reaching end 12a of the wavelength conversion element body 22 as a reaching light beam.

  The incident light beam 21 whose wavelength is the first wavelength λ1 is incident on the wavelength conversion element body 22 from the incident end 11a and travels on the optical path 71a. As the reaching light beam converted into the light having the wavelength λ2, the unconverted portion reaches the reaching end 12a as the reaching light beam having the first wavelength λ1 without being subjected to wavelength conversion.

  That is, the reaching light beam that has reached the reaching end 12a (the first reaching end) remains unconverted with the light of the second wavelength λ2 as a result of the wavelength conversion. The light of the wavelength λ1 is mixed.

  The reaching light beam that has reached the first reaching end 12a is reflected by the reflecting film 24 made of a multilayer film having a reflectivity of 99.8% or more, and what is the optical path 71a of the polarization inversion region 33 in accordance with the reflection law? The light is incident again on the wavelength conversion element main body 22 so as to travel on a different optical path 71b, and reaches the second reaching end 12b as a reaching light beam.

  Of the light reflected by the reflective film 24 and re-entering the wavelength conversion element main body 22, a part of the light having the wavelength λ1 travels along the optical path 71b to become the light having the wavelength λ2 as described above. The wavelength is converted, and the unconverted portion is not wavelength-converted and reaches the end 12b as light having the first wavelength λ1.

  That is, the light having the second wavelength λ2 as a result of the wavelength conversion and the light having the first wavelength λ1 remaining unconverted as a result of the wavelength conversion in the reaching light beam reaching the second reaching end 12b However, the ratio of the light of the second wavelength λ2 to the total amount of light is increased as compared with the reaching light beam that has reached the first reaching end 12a.

  The reaching light beam that has reached the second reaching end 12b is reflected by the reflective film 25 made of a multilayer film, and travels through the optical path 71c different from the optical path 71b of the domain-inverted region 33 to the wavelength conversion element main body 22. The light is incident again and reaches the third reaching end 12c as a reaching light beam.

  Of the light reflected by the reflective film 25 and re-entering the wavelength conversion element body 22, a part of the light having a wavelength of λ1 travels through the optical path 71c to become light having a wavelength of λ2 as described above. The wavelength is converted, the unconverted portion is not wavelength-converted and reaches the third reaching end 12c as light having the first wavelength λ1, and the emitting end 13a (as shown in the figure) is the reaching end 12c. The reaching end portion 12c and the emitting end portion 13a are the same end portion), pass through the antireflection film 26, and are output as the outgoing light beam 27 to the outside of the wavelength conversion element body 22.

  That is, the light having the second wavelength λ2 resulting from the wavelength conversion and the light having the first wavelength λ1 remaining unconverted as a result of the wavelength conversion in the reaching light beam that has reached the third reaching end 12c. However, the ratio of the light having the second wavelength λ2 to the total amount of light is increased as compared with the reaching light beam that has reached the second reaching end 12b.

  In this way, an antireflection film is formed in place of the reflection film 24 at the first arrival end 12a, and an incident light beam is incident on the wavelength conversion element body 22 from the incidence end 11a. Light of wavelength λ2 when light including light of wavelength λ2 is extracted from the first reaching end 12a out of the wavelength conversion element body 22 as an outgoing light beam without reflecting the reaching light beam that has reached the end 12a As described above, the light including the light having the wavelength λ2 passes through the antireflection film 26 from the reaching end 12c of the wavelength conversion element 20a described with reference to FIGS. 1 and 2 as described above. When the light is output to the outside of the wavelength conversion element body 22 as 27, the amount of light of the wavelength λ2 is approximately three times.

  In the present invention, such improvement in wavelength conversion efficiency can be further improved.

  As can be seen from FIGS. 1 and 2, in FIG. 1 and FIG. 2, the signal light beam reaching the reaching end is reflected by the reflecting films 24 and 25 as reflectors disposed there and re-entered the same wavelength conversion element body. In this example, the signal light beam reflected between the reflector and the reaching end portion and reflected by the reflector and the reflector again enters the wavelength conversion element body again. A condensing lens (re-incident lens) is disposed in the optical path between the re-incident end (which is apparent from the above description, in which case the re-incident end is the same as the reaching end). It is an example when it is not.

  As described above, a part of the signal light beam that enters the wavelength conversion element body 22 from the incident end 11a and travels along the optical paths 71a to 71c undergoes wavelength conversion from light having the wavelength λ1 to light having the wavelength λ2. Then, the light is output from the reaching end 12c (outgoing end 13a) through the antireflection film 26 to the outside of the wavelength conversion element body 22 as the outgoing light beam 27. According to this, the amount of light having the wavelength λ2 in the outgoing light beam 27 largely depends on how the condensing optical system condenses when the incident light beam is incident on the wavelength conversion element body 22 from the incident end 11a. It has been obtained that results.

  In the example of the method for increasing the wavelength conversion efficiency according to the technical idea of the present invention, as shown in FIGS. 1 and 2, in all the optical paths 71a to 71c from the entrance end 11a to the exit end 13a, the light is reflected on the arrival end. In the example where the body is disposed but the re-incident lens is not disposed as described above, the condensing optical system condenses light when the incident light beam is incident on the wavelength conversion element body 22 from the incident end 11a. As a method, the condensing optical system condenses so that the focal point of the condensing optical system is at or near the intermediate point 711 of the total optical path lengths of the optical paths 71a to 71c from the incident end 11a to the output end 13a. A method of making the light incident on the wavelength conversion element main body 22 can be used. As a result of experiments by the inventors of the present invention, it has been found that the wavelength conversion efficiency can be effectively increased by doing so.

  Although not shown, the emitted light beam 27 can be incident on a wavelength selection filter and selectively output light of wavelength λ2, for use in a purpose such as a light source for a microscope.

  Note that a multilayer filter that transmits light of wavelength λ2 and reflects light of wavelength λ1 is formed on the emission end portion 13a in place of or in place of the antireflection film 26, and the light of wavelength λ2 and wavelength λ1 are formed. By separating the light, the light having the wavelength λ2 is emitted from the emission end portion 13a, and the light having the wavelength λ1 is emitted from the other end portion, thereby forming a small light source. This configuration can also be applied to the following examples.

  The wavelength conversion element described with reference to FIGS. 1 and 2 substantially has an optical path length for performing wavelength conversion of incident light by reflecting the reaching light beam by the reflector and re-entering the wavelength conversion element body. It is an example of the wavelength conversion method of lengthening.

  Examples of the wavelength of the incident light and the wavelength of the output light as a result of wavelength conversion include a wavelength conversion element having a first wavelength λ1 of 1120 nm and a second wavelength λ2 of 560 nm, and a second wavelength λ1 of 1160 nm and a second wavelength λ1. For each wavelength conversion element having a wavelength λ2 of 580 nm, each wavelength conversion element in which the reflection film having a high reflectance with respect to each wavelength λ1 and λ2 in each wavelength conversion element is formed. The wavelength conversion element which has was able to be obtained.

  In addition to the above, in order to obtain a wavelength conversion element having good wavelength conversion efficiency, a more remarkable effect can be brought about by various measures. Examples of the device include increasing the parallelism of the element surface at each reaching end, the parallelism between the boundary of the domain-inverted region and the element surface, and the like.

  As one preferred method, it is possible to increase the parallelism between the element surfaces in the relationship where the incident end portion, the arrival end portion, and the emission end portion of the wavelength conversion element main body are located opposite to each other. .

  As a preferred example, in FIGS. 1 and 2, the dimension of the wavelength conversion element body 22 that is effective in the wavelength conversion of the wavelength conversion element body 22 in the vertical direction is referred to as the element length of the wavelength conversion element body 22. When the thickness is 30 mm, the parallelism of the surface including the incident end portion 11a and the reaching end portion 12b of the wavelength conversion element body 22 and the surface including the reaching end portion 12a and the emitting end portion 13a (the reaching end portion 12c) is approximately. By configuring within 1 minute, and configuring the parallelism between the boundary surfaces of the domain-inverted regions within approximately 1 minute, a wavelength conversion element having even better wavelength conversion efficiency can be obtained.

  FIGS. 3 and 4 are diagrams for explaining the wavelength conversion element of the present invention in more detail. FIG. 3 shows the opposing surfaces on which the reflectors of the element are disposed when a parallel plate element is used as the wavelength conversion element body. FIG. 4 is a cross-sectional view for explaining the parallelism between the boundary of the domain-inverted region of the wavelength conversion element body of FIG. 3 and the element surface.

  3 and 4, reference numeral 34 a is a line extending from the surface including the incident end 11 a and the arrival end 12 b of the wavelength conversion element body 22, and 34 b is the arrival end 12 a and the emission end of the wavelength conversion element body 22. A line extending the surface including the reaching end 12c to be 13a, 35a1 and 35b1 are lines extending the boundary surface of the domain-inverted region, 34 is a symbol indicating the parallelism between the lines 34a and 34b, and 35a is a line 34a. Reference numeral 35 represents a parallelism of the line 35a1, reference numeral 35b represents a parallelism of the lines 35b1 and 34b, and reference numeral 39 represents a width of the domain-inverted region.

  The wavelength conversion element body 22 described with reference to FIGS. 3 and 4 is a plane in which a surface 34a including the incident end portion 11a and the reaching end portion 12b and a surface 34b including the reaching end portion 12a and the incident end portion 13a are parallel to each other. Is formed.

  3 and 4, the dimension of the domain-inverted region 33 perpendicular to the normal line intersecting both surfaces 34a and 34b and in the vertical direction in the figure is called the width of the domain-inverted region. The dimension of the wavelength conversion element body 22 in the normal direction intersecting both surfaces of 34b is referred to as the element length of the wavelength conversion element body 22. When the element length is set to 30 mm, it is preferable for the above reason that the parallelism indicated by reference numeral 34, reference numeral 35a, and reference numeral 35b is set within approximately one minute.

  The width in the plane including the optical path of the domain-inverted region 33 indicated by the arrow with reference numeral 39 is the case where there is one reaching end where a reflector that reflects the reaching light and re-enters the wavelength conversion element body is disposed. In other words, when the return of the optical path (path) incident on the wavelength conversion element main body is one time (two paths), it is preferable to configure at least 2 mm. The example shown in FIGS. 3 and 4 is the case where the optical path is folded twice, and the width of the polarization inversion region 33 on the surface including the optical path is 3 mm or more. The width in the plane including the optical path of the domain-inverted region can also be expressed by approximating in the direction orthogonal to the optical path of the incident light first incident on the wavelength conversion element body in the plane.

  By adopting such a configuration, it was possible to realize the wavelength conversion element of the present invention that is small in size, has high wavelength conversion efficiency, and can be applied to high power.

  FIG. 5 is a diagram for explaining the wavelength conversion element of the present invention in more detail, and for explaining the parallelism between the boundary of the polarization inversion region of the wavelength conversion element body and the surface of the external reflecting mirror.

  In FIG. 5, reference numerals 37a and 37b denote lines obtained by extending the reflecting surface of the external reflecting mirror 29, and 36a and 36b denote the parallelism of the boundary between the reflecting surface of the external reflecting mirror 29 and the polarization inversion region.

  The wavelength conversion element body 22 described with reference to FIG. 5 has a surface including the incident end portion 11a and the reaching end portion 12e and a surface including the reaching end portion 12d and the incident end portion 13b formed in parallel planes. .

  In FIG. 5, it is preferable for the same reason as described above that the parallelism indicated by reference numerals 37a and 37b is set within approximately one minute.

  For the same reason as described above, the parallelism of the element surface in the vicinity of the incident end and the arrival end, and the parallelism of the boundary between the domain-inverted region and the surface of the element surface are preferably within one minute.

  In FIG. 5, the antireflection film 28 at the incident end 11a and the antireflection film 28 at the reaching end 12e are formed as a continuous integral antireflection film, and the antireflection at the reaching end 12d. The antireflection film 28 at the portion of the film 28 and the emission end portion 13b (the reaching end portion 12f) is also formed as a continuous integral antireflection film.

  According to the technical idea of the present invention, the preferable condition of the domain-inverted element having the domain-inverted region according to the present invention is that the condition 1 is that the incident surface or re-incident surface of the wavelength conversion element and the boundary surface between the domain-inverted region are 1 minute. In condition 2, the output surface of the wavelength conversion element or the surface of the arrival end and the boundary surface of the domain-inverted region are parallel to each other with an opening angle of less than 1 minute. And the condition 3 is that the boundary surfaces of the plurality of domain-inverted regions are formed in parallel with each other at an opening angle of 1 minute or less. The width is at least 2 mm in a direction perpendicular to the optical path of the incident light first incident on the wavelength conversion element and in the plane including the optical path and the optical path of the next re-incident light, and Condition 5 is the wavelength conversion The incident of the element It is preferable that the end surface and the opposite surface are formed in parallel with each other at an opening angle of 1 minute or less, and it is preferable that at least two conditions are satisfied, and it is particularly preferable that five conditions be satisfied.

  In the example of the method for increasing the wavelength conversion efficiency according to the technical idea of the present invention, as shown in FIGS. 1 and 2, in the optical paths 71a to 71c from the incident end 11a to the exit end 13a, a reflector is provided at the arrival end. Is an example in which a re-incidence lens is not disposed. As a method of condensing the condensing optical system when an incident light beam is incident on the wavelength conversion element body 22 from the incident end portion 11a, FIG. 1, although not shown in FIG. 2, the volume when viewed as the optical path length of the signal light beam in all the optical paths 71a to 71c from the incident end 11a to the exit end 13a is minimized or as close as possible to the minimum. It is possible to use a method in which the light is condensed so as to be in a state and an incident light beam is incident on the wavelength conversion element body 22. As a result of experiments by the inventor of the present invention, it has been confirmed that the wavelength conversion efficiency can be effectively increased in this way.

  By adopting such a configuration, a small wavelength conversion element with high wavelength conversion efficiency could be realized.

  FIG. 6 is a diagram for explaining an example of a wavelength conversion element according to the technical idea of the present invention, and is a different example of the condensing optical system from the examples of FIG. 1 and FIG. Description will be made using a cross section including an optical path of light subjected to wavelength conversion of the wavelength conversion element.

  In FIG. 6, reference numeral 20c is a wavelength conversion element used in the wavelength conversion device of the present invention, 12a1 and 12b1 are arrival end parts, 12a2 and 12b2 are re-incidence end parts, 28 is an antireflection film, and 29a and 29b are reflectors. External reflecting mirrors, 30a and 30b are lenses, 50a1, 50b1 and 50c1 are optical paths, and 50a to 50c are central points (also referred to as intermediate points) as optical path lengths of the optical paths. When the reaching end portion 12a1 and the re-incident end portion 12a2 are close to each other, they may be handled as the reaching end portion 12a similarly to FIG. 1, and also when the reaching end portion 12b1 and the re-incident end portion 12b2 are close to each other. 1 can be treated as the reaching end 12b. In each lens 30a, 30b, the signal light beam that has reached each reaching end of the illustrated wavelength conversion element body 22 passes through each lens 30a, 30b, as shown, and is reflected by each external reflecting mirror 29a, 29b. When the light passes through the lenses 30a and 30b again and reenters the wavelength conversion element body 22, it is a re-incident lens that is appropriately condensed and re-entered according to the technical concept of the present invention. The optical path 50a1 is an optical path between the incident end portion 11a and the reaching end portion 12a1, the center point 50a is a center point when viewed as the optical path length of the optical path 50a1, and the optical path 50b1 is between the re-incident end portion 12a2 and the reaching end portion 12b1. In the optical path, the center point 50b is the center point when viewed as the optical path length of the optical path 50b1, the optical path 50c1 is the optical path between the re-incidence end portion 12b2 and the reaching end portion 13a, and the center point 50c is viewed as the optical path length of the optical path 50c1. Is the center point.

  The focal points of the lenses 30a and 30b when the signal light beam is re-incident on the wavelength conversion element main body 22 in the example of the wavelength conversion apparatus using the wavelength conversion method for increasing the wavelength conversion efficiency using the present invention are respectively external reflection mirrors. The signal light beam reflected by 29a and 29b and re-entering the wavelength conversion element main body 22 is focused on the central points 50b1 and 50c1 as the optical path lengths of the respective optical paths indicated by reference numerals 50b and 50c. ing.

  More specifically, although not shown in FIG. 6, the condensing optical system arranged at the front stage of the incident end of the wavelength conversion element main body 22 is focused on the central point 50a of the optical path 50a1. The incident light beam 21 as a signal light beam is transmitted through the antireflection film 28 and is incident on the wavelength conversion element body 22 from the incident end 11a, so that the wavelength conversion element body 22 is advanced and high conversion is performed. Wavelength conversion is performed with efficiency, and the signal light beam that has reached the reaching end 12a1 is transmitted through the antireflection film 28, passes through the lens 30a, and reaches the external reflecting mirror 29a as a reflector, and is reflected by the external reflecting mirror 29a. The reflected light passes through the lens 30a again (the lens 30a functions as the re-incidence lens 30a), passes through the antireflection film 28, and passes through the re-incident end 12a2 to the wavelength conversion element body 2 To re-enter the. At this time, the re-incidence optical system is adjusted so that the focus of the re-incidence lens 30a is the center point 50b of the optical path 50b1.

  The signal light beam re-entered to the wavelength conversion element body 22 from the re-incident end 12a2 is converted with high conversion efficiency while traveling through the wavelength conversion element body 22, and the signal light beam reaching the reaching end 12b1 is converted. Then, the light passes through the antireflection film 28, reaches the external reflecting mirror 29b as a reflector through the lens 30b, is reflected by the external reflecting mirror 29b, and is again the lens 30b (the lens 30b functions as the re-incidence lens 30b). ) Through the antireflection film 28 and re-enter the wavelength conversion element body 22 from the re-incident end 12b2.

  The signal light beam re-incident on the wavelength conversion element body 22 from the re-incidence end portion 12b2 is subjected to wavelength conversion with high conversion efficiency while advancing the wavelength conversion element body 22, and the signal light beam reaching the arrival end portion 12c is The antireflection film 28 is transmitted from the reaching end portion 12 c serving as the emission end portion 13 a and emitted as the emission light beam 27.

  As described above, the condensing position of the incident light beam on the wavelength conversion element main body using the condensing optical system in the embodiment of the present invention is such that the focal point of the condensing optical system is the wavelength conversion element main body. The signal light beam reaching the arrival end or the signal light beam emitted from the arrival end is reflected by a reflector disposed at or near the arrival end between the incident end and the emission end of the same A reflector that re-enters the wavelength conversion element body is disposed, but is incident when a condenser lens as a re-incidence lens is not disposed in the optical path between the reflector and the end of the wavelength conversion element body. The position corresponding to or in the vicinity of the intermediate point of the total optical path length between the end and the exit end, and the reflector and the re-incident lens are arranged between the entrance end and the exit end of the wavelength conversion element body If not, enter and exit A position corresponding to or near the midpoint of the total optical path length between the end portions, and the reflector and the re-incident lens are disposed in the optical path between the incident end portion and the exit end portion of the wavelength conversion element body. It is understood that the characteristic is that it is at or near the midpoint of the total optical path length between the incident end and the arrival end immediately before the re-incidence lens.

  When the wavelength conversion element has at least one re-incidence lens, a signal light beam that passes through the re-incident lens and re-enters the wavelength conversion element main body is reflected by the re-incident lens on the wavelength conversion element main body. The wavelength conversion element body is configured to re-enter the wavelength conversion element body so as to be condensed at a predetermined position, and the wavelength conversion element body has the predetermined position corresponding to the re-incidence lens and the wavelength conversion of the wavelength conversion element body. The same wavelength conversion is performed by reflecting the signal light beam reaching the arrival end or the signal light beam emitted from the arrival end with a reflector disposed at or near the arrival end between the emission ends of the element body. A reflector that re-enters the element body is disposed, but another re-incident lens other than the re-incident lens is disposed in the optical path between the reflector and the wavelength conversion element body. If not, the wavelength conversion element body constituting the wavelength conversion element at or near the midpoint of the total optical path length between the re-incidence lens and the output end of the wavelength conversion element body In the case where neither a reflector nor another re-incidence lens other than the re-incidence lens is arranged between the re-incidence lens and the emission end of the wavelength conversion element body, the re-incidence lens and the emission end Between the re-incident lens of the wavelength conversion element body and the light path between the exit end of the wavelength conversion element body When another re-incidence lens other than the lens is arranged, the middle of the total optical path length between the re-incident end immediately after the re-incident lens and the arrival end immediately before the other re-incident lens At or near the point It can be seen that it is characterized in that.

  By using an apparatus with such a simple configuration, the adverse effect of the spread of the signal light beam incident on or re-incident on the wavelength conversion element body 22 is prevented, the wavelength conversion efficiency in the wavelength conversion element body 22 is increased, and the outgoing light This brings about a great effect that the quality of the beam 27 can be improved.

  An example of a wavelength conversion method for improving the wavelength conversion efficiency using the present invention will be further described. As a method for increasing the wavelength conversion efficiency in the wavelength conversion element body 22 from a different viewpoint, it is conceivable to appropriately increase the light density in the wavelength conversion element body 22 of the signal light beam subjected to wavelength conversion.

  As a preferable example of the present invention as a result of the study of the inventors of the present invention, although not shown in its entirety in FIG. 6, in FIG. 6, the wavelength conversion element main body between the incident end portion 11a and the outgoing end portion 13a. The volume of the signal light beam in the wavelength converter 22 can be reduced to increase the optical density of the signal light beam in the wavelength conversion element body 22 and the wavelength conversion efficiency can be increased.

  More specifically, in FIG. 6, an incident light beam 21 as a signal light beam to be subjected to wavelength conversion is incident on the wavelength conversion element main body 22 from the incident end 11a and the wavelength conversion element main body 22 is advanced to reach the arrival end. In order to reach 12a1, the incident light beam incident method by the condensing optical system arranged in front of the incident end of the wavelength conversion element main body 22 (not shown in FIG. 6) is changed from the incident end 11a to the wavelength conversion element. By making the volume of the signal light beam incident on the main body 22 between the incident end portion 11a and the reaching end portion 12a1 in the wavelength conversion element main body 22 be in a minimum or near minimum state, the wavelength conversion efficiency can be improved. Can be effectively increased.

  Then, the signal light beam that has reached the reaching end 12a1 is transmitted through the antireflection film 28, reaches the external reflecting mirror 29a as a reflector through the lens 30a, is reflected by the external reflecting mirror 29a, and is re-incidence lens 30a. Then, the light is transmitted through the antireflection film 28 and reentered to the wavelength conversion element body 22 from the re-incident end 12a2. At this time, the re-incident condensing optical system having the re-incident lens 30a has a re-incident end 12a2 in the wavelength conversion element main body 22 of the signal light beam re-incident on the wavelength conversion element main body 22 from the re-incident end 12a2. The wavelength conversion efficiency can be effectively increased by setting the volume between the reaching end portion 12b1, which is the reaching end portion immediately before the next re-incidence lens 30b, to a minimum or near minimum state.

  In this way, the signal light beam re-entered to the wavelength conversion element body 22 from the re-incidence end portion 12a2 is subjected to wavelength conversion with high conversion efficiency while traveling through the wavelength conversion element body 22, and reaches the reaching end portion 12b1. The signal light beam is transmitted through the antireflection film 28, passes through the lens 30b, reaches the external reflecting mirror 29b as a reflector, is reflected by the external reflecting mirror 29b, and passes again through the re-incidence lens 30b to be reflected. The light is transmitted through the prevention film 28 and reentered to the wavelength conversion element main body 22 from the re-incident end 12b2. At this time, the re-incident condensing optical system having the re-incident lens 30b has a re-incident end 12b2 in the wavelength conversion element main body 22 of the signal light beam re-incident on the wavelength conversion element main body 22 from the re-incident end 12b2. In addition, the wavelength conversion efficiency can be effectively increased by setting the volume between the reaching end portion 12c, that is, the next reaching end portion, that is, the emission end portion 13a, to a minimum or near minimum state.

  In this way, the signal light beam re-entered to the wavelength conversion element body 22 from the re-incidence end portion 12b2 is subjected to wavelength conversion with high conversion efficiency while traveling through the wavelength conversion element body 22, and reaches the reaching end portion 12c. The signal light beam is transmitted through the antireflection film 28 from the arrival end portion 12 c as the emission end portion 13 a and is emitted as the emission light beam 27.

  As described above, the condensing position of the incident light beam to the wavelength conversion element body using the condensing optical system in the embodiment of the present invention is the incident end portion and the emission end portion of the wavelength conversion element body. In the meantime, the signal light beam reaching the reaching end portion or the signal light beam emitted from the reaching end portion is reflected by a reflector disposed at or near the reaching end portion and re-enters the same wavelength conversion element main body. A signal light beam between the incident end and the exit end when no re-incidence lens is disposed in the optical path between the reflector and the re-incident end of the wavelength conversion element. Is the light condensing position or the vicinity thereof that minimizes the volume of the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path that passes through, the incident end and the emission end of the wavelength conversion element main body Reflection between parts In the case where neither the re-incidence lens nor the re-incidence lens is arranged, the volume of the signal light beam in the wavelength conversion element body is minimized when viewed as the optical path length of the optical path through which the signal light beam passes between the entrance end and the exit end. When the re-incident lens is disposed in the optical path between the incident end and the output end of the wavelength conversion element body, the incident end and the re-incident lens A condensing position that makes the volume of the signal light beam within the wavelength conversion element body minimum or close to the minimum when viewed as the optical path length of the optical path through which the signal light beam passes between the reaching ends immediately before Or it turns out that it is the feature in the vicinity.

  When the wavelength conversion element has at least one re-incidence lens, a signal light beam that passes through the re-incidence lens and re-enters the wavelength conversion element is moved to a predetermined position of the wavelength conversion element by the re-incidence lens. The wavelength conversion element is re-incident on the wavelength conversion element, and the predetermined position of the wavelength conversion element is the re-incidence lens of the wavelength conversion element main body constituting the wavelength conversion element. And the signal light beam that has reached the arrival end or the signal light beam that has exited from the arrival end is reflected by a reflector disposed at or near the arrival end. A reflector that re-enters the same wavelength conversion element body is disposed, but another re-incidence lens other than the re-incidence lens is disposed in the optical path between the reflector and the wavelength conversion element body. If not placed, the volume of the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between the re-incidence lens and the emission end of the wavelength conversion element body Is a condensing position at or near the condensing position, and the reflector is also different from the re-incidence lens between the re-incident lens of the wavelength conversion element body and the exit end of the wavelength conversion element body. If the re-incidence lens is not arranged, the volume of the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between the re-incidence lens and the emission end is The light condensing position or the vicinity thereof to be minimized, the reflector and the re-incidence lens in the optical path between the re-incidence lens of the wavelength conversion element body and the emission end of the wavelength conversion element body When another re-incidence lens is arranged, the optical path of the optical path through which the signal light beam passes between the re-incident end immediately after the re-incident lens and the arrival end immediately before the other re-incident lens It can be seen that it is characterized by being at or near the condensing position that minimizes the volume of the signal light beam in the wavelength conversion element body when viewed as a length.

  As described above, by using the technical idea of the present invention, it is possible to effectively improve the wavelength conversion efficiency and obtain a high-quality wavelength-converted outgoing light beam by using a small and simple device.

  In the above example, a functional element capable of reflecting a light beam having a specific wavelength as a reflector with a high reflectance of 99% or more and transmitting a light beam having a wavelength different from the specific wavelength is used. Thus, a light beam having a wavelength at the reflector can be extracted and used depending on the application.

  Further, in FIG. 6, the external reflecting mirrors 29a and 29b can be arranged close to the wavelength conversion element main body 22 without using the re-incidence lenses 30a and 30b, so that the same configuration as in FIGS.

  FIG. 7 is a diagram for explaining a main part of the wavelength conversion device as an embodiment of the present invention. In the wavelength conversion device using two wavelength conversion elements, the first wavelength conversion element is provided on one side of the connecting lens 30. This is an example in which a second wavelength conversion element is arranged on the other side of the connecting lens 30.

  In FIG. 7, reference numeral 20e is a wavelength conversion device as an embodiment of the present invention, 20e1 and 20e2 are wavelength conversion elements as embodiments of the present invention, 27c and 27d are outgoing light beams, 27c1 is an incident light beam, 30 Is a connecting lens.

  The wavelength conversion device 20e has a configuration in which a wavelength conversion element 20e1 and a wavelength conversion element 20e2 are connected in series via a lens in the main part, and although not shown in the drawing, the wavelength conversion device 20e has a wavelength in the optical path of the incident light beam 21. A laser light source and a condensing optical system for guiding incident light to the incident end shown in the figure are arranged upstream of the conversion element 20e1, and a wavelength selection filter made of, for example, a multilayer film is arranged downstream of the outgoing light beam 27d. In addition, with such a set of configurations, a plurality of outgoing lights having different wavelengths can be extracted.

  FIG. 7 shows that the signal light that has reached the arrival end or the arrival end is emitted between the incident end and the emission end of the wavelength conversion element main body 22 constituting the second wavelength conversion element 20e2. A reflector for reflecting the signal light with a reflector disposed at or near the reaching end and re-entering the same wavelength conversion element main body is disposed, but re-incidence of the reflector and the second wavelength conversion element is provided. This is an example in which a condensing lens as a re-incidence lens is not disposed in the optical path between the end portions.

  The focal point of the connecting lens 30 is an intermediate as the optical path length of the front optical path in the wavelength conversion element body 22 with the outgoing light beam 27c from the first wavelength conversion element 20e1 as the incident beam 27c1 to the second wavelength conversion element 20e2. The focal point is formed so that an image is formed at a point, that is, preferably at the central point 50d or in the vicinity thereof. Thereby, wavelength conversion efficiency can be improved effectively. The wavelength conversion efficiency is further increased by making the method of condensing the incident beam 21 on the first wavelength conversion element 20e1 the same as the method of condensing the incident beam 27c1 on the second wavelength conversion element 20e2. Can do.

  By configuring in this way, it is possible to provide a wavelength conversion device that is small, inexpensive, and capable of performing excellent wavelength conversion.

  When the configurations of the first wavelength conversion element 20e1 and the second wavelength conversion element 20e2 are variously changed, the respective light collection methods described with reference to FIGS. An optical method can be used, and a condensing method in which they are appropriately combined can be used.

  FIG. 8 is a diagram for explaining a main part of the wavelength conversion device as an embodiment of the present invention, in which the first wavelength conversion element and the second wavelength conversion element are arranged on one side of the reflector.

  In FIG. 8, reference numeral 250 denotes a wavelength conversion device, 251 and 252 denote wavelength conversion elements, 253 and 254 denote wavelength conversion element bodies, 255 denotes an incident light beam, 256 denotes an outgoing light beam, 257 to 260 denote antireflection films, and 261. 262 is an optical path in the wavelength conversion element main body, 261a is an intermediate point as an optical path length between the incident end 271 and the emission end 272 of the wavelength conversion element main body 253 in the optical path 261, and 262a is a wavelength conversion element main body in the optical path 262. An intermediate point as an optical path length between the entrance end 273 and the exit end 274 of 254, 263 and 264 are connection lenses, 265 is a prism as a reflector, and 280 is a connection lens optical path.

  As illustrated, the wavelength conversion device 250 has a configuration in which a first wavelength conversion element 253 and a second wavelength conversion element 254 are disposed on one side of the reflector 265.

  The lens optical path 280 is an optical path that passes through the connection lenses 263 and 264 from the emission end 272 of the first wavelength conversion element 253 to the incident end 273 of the second wavelength conversion element 254, and is optical by the prism 265 as a reflector. Is wrapped.

  The wavelength conversion device 250 is an example in which there are a plurality of connection lenses in the optical path between two wavelength conversion elements as shown in the figure, and includes a connection lens 263 and a connection lens 264.

  Although not shown, the incident light beam 255 to the wavelength conversion element main body 253 is collected by the condensing optical system for incident light so that the focal point of the condensing optical system is in the vicinity of the intermediate point 261a of the optical path 261. The light is incident on the wavelength conversion element body 253. The incident light beam that has passed through the connecting lens optical path 280 and enters the wavelength conversion element body 254 is collected by the connecting lens as the condensing optical system so that the focal point of the condensing optical system is in the vicinity of the intermediate point 262a of the optical path 262. The light is incident on the wavelength conversion element body 254.

  In this way, by configuring the wavelength conversion device 250 by managing the condensing optical system of the incident light to each wavelength conversion element body, the configuration is simple, compact, high in wavelength conversion efficiency, high quality, high quality A power coherent light source can be manufactured at low cost, and can be configured as a wavelength tunable light source according to the purpose of use.

  Further, in the wavelength converter 250 having the configuration shown in FIG. 8, each condensing optical system is connected from the incident end to the output end of the wavelength conversion element main bodies 253 and 254 in the same manner as in the above embodiment. By reducing the volume of the signal light beam in the wavelength conversion element body between the two, the optical density of the signal light beam in the wavelength conversion element body can be increased, and the wavelength conversion efficiency can be increased.

  More specifically, in FIG. 8, an incident light beam 255 as a signal light beam to be subjected to wavelength conversion is incident on the wavelength conversion element body 253 from the incident end 271 and travels through the wavelength conversion element body 253 while reaching the arrival end. In order to reach the portion 272, the incident light beam incident method by a condensing optical system (not shown in FIG. 8) is used as the wavelength conversion element body 253 of the signal light beam incident on the wavelength conversion element body 253 from the incident end 271. By managing the condensing optical system so that the volume between the incident end portion 271 and the arrival end portion 272 is minimized or close to the minimum, the wavelength conversion efficiency can be effectively increased.

  Further, incident light that is emitted from the wavelength conversion element 251 and enters the wavelength conversion element body 254 of the wavelength conversion element 252 through the connection lens optical path 280 is disposed between the emission end 272 and the incident end 273. The volume between the incident end 273 and the arrival end 274 in the wavelength conversion element main body 254 of the signal light beam incident on the wavelength conversion element main body 254 from the incident end 273 in the condensing optical system including the connecting lens 264 is as follows. By managing the condensing optical system so as to be in the minimum or near-minimum state, the wavelength conversion efficiency can be further effectively increased.

  In FIG. 8, the connection lens 263 and the connection lens 264 are used as the connection lens. However, instead of the two lenses of the connection lens 263 and the connection lens 264, one continuous lens can be used. In this way, further downsizing and cost reduction can be achieved. In particular, when the size of the wavelength conversion element in FIG.

  Although an example in which the prism 265 is used as the reflector is shown, various variations are possible for this reflector.

  The wavelength converter described with reference to FIG. 8 has a practically significant effect that the input / output can be provided on the same side of the wavelength converter in addition to the advantage as a small wavelength converter having a short length.

  Further, the wavelength conversion element main body as shown in FIG. 6, for example, as described with reference to FIG. 6 may be used for a part or all of the wavelength conversion elements constituting the wavelength conversion device illustrated in FIGS. In the case of using a wavelength conversion element having a re-incidence lens disposed between them, the above-described condensing technical concept described with reference to FIG. 6 is applied, and wavelength conversion efficiency is good, and wavelength-converted high power and good quality It can be easily understood from the above description that a light source can be provided.

  As described above, the present invention is simple in structure, small in size, high in wavelength conversion efficiency, can produce a high-quality, high-power coherent light source at low cost, and has the above-described characteristics according to the purpose of use. This brings about a great effect that the wavelength tunable light source can also be provided at low cost.

  As described above, the wavelength conversion device and the wavelength conversion method as the embodiment of the present invention have been described with reference to the drawings. However, the present invention is not limited to this, for example, configurations of various lenses, reflectors, and the like. Many variations are possible, such as the configuration.

  As described above, the present invention provides a light source that can be used in a wide range of fields such as an optical communication field, a medical field, a microscope, and a measurement field as a low-cost coherent light source that can be realized with high quality, small size, and high power. be able to.

It is a figure explaining the wavelength conversion element as an Example of this invention. It is a figure explaining the wavelength conversion element as an Example of this invention. It is a figure explaining the parallelism of the surface of the wavelength conversion element main body as an Example of this invention. It is a figure explaining the parallelism of the boundary of the polarization inversion area | region of the wavelength conversion element main body of FIG. 3, and an element surface. It is a figure explaining a wavelength conversion element in more detail, and is a figure explaining the parallelism of the boundary of the polarization inversion area | region of a wavelength conversion element main body, and the surface of an external reflective mirror. It is a figure explaining the example of the wavelength conversion element used for this invention. It is a figure explaining the principal part of the wavelength converter as an Example of this invention. It is a figure explaining the principal part of the wavelength converter as an Example of this invention. It is a figure explaining the conventional wavelength conversion element. It is a figure explaining the conventional wavelength conversion element. It is a figure explaining the conventional optical parametric oscillator. It is a figure explaining the conventional wavelength conversion element.

Explanation of symbols

11a: incident end portions 12a to 12c, 12a1, 12b1: reaching end portions 12a2, 12b2: re-incident end portions 13a: emitting end portions 20a, 20c, 20e1, 20e2, 200, 251, 252, 1100: wavelength conversion elements 20e, 250: Wavelength conversion device 21, 27c1, 204, 221, 255: Incident light beam 22,253, 254: Wavelength conversion element body 23, 26, 28, 202, 203, 205, 219, 257 to 260: Antireflection film 24 , 25: Reflective films as reflectors 27, 27c, 27d, 256: outgoing light beams 29a, 29b: external reflectors 30, 263, 264: connection lenses 30a, 30b: re-incident lenses 33, 209: polarization inversion regions 34 : Symbol representing the parallelism between the line 34a and the line 34b 34a: The incident end and the reaching end of the wavelength conversion element body are Line 34b extended from the included surface 34b: Line extended from the surface including the arrival end and the output end of the wavelength conversion element main body 35a: Symbols 35a1, 35b1: Denoting the parallelism of the line 34a and the line 35a1 Line 35b extended from the boundary surface: Symbols 36a, 36b representing the parallelism of the lines 35b1 and 34b: Symbols 37a, 37b explaining the parallelism of the boundary between the reflecting surface of the external reflector and the polarization inversion region 37a, 37b: External reflector 29 Line 39 obtained by extending the reflection surface of 39: Reference numeral 50a to 50d, 261a, 262a, 711 for explaining the width of the domain-inverted region: Intermediate point (center point) as the optical path length of the optical path
50a1, 50b1, 50c1, 71a-71c, 261, 262: optical path 106: nonlinear crystal 221: laser 222: condensing optical system 225: incident surface 226: exit surface 265: prism 280: connecting lens optical path

Claims (65)

  In the present invention, wavelength conversion is performed on light having a first wavelength λ1 included in incident light incident on a wavelength conversion element body, which will be described later, to light having a second wavelength λ2, which is a wavelength different from the first wavelength λ1. The element itself that can be used is called the wavelength conversion element body, the end of the wavelength conversion element body that makes incident light incident on the wavelength conversion element body is defined as the incident end, and the incident light enters the wavelength conversion element body. The wavelength converting element main body travels while undergoing wavelength conversion from the light having the first wavelength λ1 to the light having the second wavelength λ2, and includes light having the first wavelength λ1 and light having the second wavelength λ2. An end portion different from or near the end portion of the wavelength conversion element main body that reaches as light is defined as a reaching end portion of the wavelength conversion element main body, and the wavelength conversion is performed in the reaching end portion. The end that takes out the light that arrives and receives it as the outgoing light Defines the vicinity of the end as the exit end of the wavelength conversion element body, and the incident light including the light of the first wavelength λ1 before entering the wavelength conversion element body and the incident light enter the wavelength conversion element body The incident light including the light having the first wavelength λ1 and the light having the second wavelength λ2 that travels in the wavelength conversion element body while being subjected to wavelength conversion, and the incident light incident on the wavelength conversion element body are the wavelength conversion element. Each of the outgoing lights that have traveled through the body and have been subjected to wavelength conversion and emitted from the wavelength conversion element main body, or collectively referred to as signal light, an optical system or the like disposed in the wavelength conversion element main body, A wavelength conversion device in which a wavelength conversion device main body or the like is mounted in a case or the like is referred to as a wavelength conversion device, and in the wavelength conversion device using at least two of the wavelength conversion devices, the wavelength conversion device is a signal light beam subjected to wavelength conversion. In the light path And having at least one wavelength conversion optical circuit unit having at least two wavelength conversion elements connected in series via a lens (hereinafter also referred to as a connecting lens), and at least one of the wavelength conversion devices The wavelength conversion optical circuit section includes an emission end of one wavelength conversion element (hereinafter also referred to as a first wavelength conversion element) of two wavelength conversion elements connected in series via the connection lens. An optical path of a signal light beam including an optical path passing through the connection lens between incident ends of the other wavelength conversion element (hereinafter also referred to as a second wavelength conversion element) is also referred to as a connection lens optical path. The signal light beam emitted from the wavelength conversion element enters the second wavelength conversion element so that it passes through the connection lens optical path and is condensed by the connection lens at a predetermined position of the second wavelength conversion element. The predetermined position of the second wavelength conversion element reaches between the incident end and the emission end of the wavelength conversion element main body constituting the second wavelength conversion element. A reflector for reflecting the signal light beam reaching the end or the signal light beam emitted from the reaching end by a reflector disposed at or near the reaching end and re-entering the same wavelength conversion element body is disposed. However, when a condensing lens (hereinafter also referred to as a re-incidence lens) is not disposed in the optical path between the reflector and the end of the second wavelength conversion element, the incident end and the exit end The reflector is also re-incident between the incident end and the exit end of the wavelength conversion element main body constituting the second wavelength conversion element at or near the position corresponding to the intermediate point of the total optical path length between Input end if no lens is placed The optical path between the incident end and the exit end of the wavelength conversion element main body constituting the second wavelength conversion element, which is at or near the midpoint of the total optical path length between the exit ends. When the reflector and the re-incidence lens are arranged, the position is equivalent to or in the vicinity of the intermediate point of the total optical path length between the incident end and the arrival end immediately before the re-incidence lens. And a wavelength converter.   2. The wavelength conversion device according to claim 1, wherein an incident light beam incident on the first wavelength conversion element in at least one of the wavelength conversion optical circuit units of the wavelength conversion device is the wavelength of the first wavelength conversion element. The first wavelength conversion element is configured to enter the first wavelength conversion element so as to be condensed at a predetermined position, and the predetermined position of the first wavelength conversion element constitutes the first wavelength conversion element. A reflector in which the signal light beam reaching the arrival end or the signal light beam emitted from the arrival end is arranged at or near the arrival end between the incident end and the emission end of the wavelength conversion element main body In the case where the reflector that is reflected by the light source and re-enters the same wavelength conversion element main body is disposed, but no re-incidence lens is disposed in the optical path between the reflector and the end of the first wavelength conversion element. The incident end The position corresponding to or in the vicinity of the intermediate point of the total optical path length between the emission end portions, and between the incident end portion and the emission end portion of the wavelength conversion element main body constituting the first wavelength conversion element. When neither a reflector nor a re-incidence lens is arranged, it is at or near the position corresponding to the intermediate point of the total optical path length between the entrance end and the exit end, and constitutes the first wavelength conversion element. When the reflector and the re-incident lens are arranged in the optical path between the incident end and the outgoing end of the wavelength conversion element body, the distance between the incident end and the arrival end immediately before the re-incident lens A wavelength converter characterized by being located at or near the midpoint of the total optical path length.   3. The wavelength conversion device according to claim 1, wherein at least one wavelength conversion element has at least one re-incident lens, and the signal light beam passes through the re-incident lens and reenters the wavelength conversion element. Is re-incident on the wavelength conversion element so as to be condensed at a predetermined position of the wavelength conversion element by the re-incident lens, and the predetermined position of the wavelength conversion element is Between the re-incident lens of the wavelength conversion element main body and the emission end of the wavelength conversion element main body constituting the signal light beam reaching the arrival end or the signal light beam emitted from the arrival end A reflector that is reflected by a reflector disposed at or near the arrival end and re-enters the same wavelength conversion element main body is disposed, but the reflector and the wavelength conversion element main body If no other re-incidence lens other than the re-incidence lens is arranged in the optical path, the entire optical path between the re-incident end immediately after the re-incident lens and the output end of the wavelength conversion element body The reflector is also located between the re-incident lens of the wavelength conversion element main body constituting the wavelength conversion element and the exit end of the wavelength conversion element main body at or near the position corresponding to the middle point of the length. If another re-incidence lens other than the incident lens is not arranged, the position corresponding to the intermediate point of the total optical path length between the re-incidence end and the exit end immediately after the re-incidence lens or the vicinity thereof In the optical path between the re-incidence lens of the wavelength conversion element body constituting the wavelength conversion element and the exit end of the wavelength conversion element body, another reflector and the re-incidence lens are different from each other. If an incident lens is placed Wavelength converter, characterized in that the position or the vicinity thereof corresponding to the midpoint of the total optical path length between the arrival end of the previous re-entering end and the other re-entering lens immediately following the incident lens.   4. The wavelength conversion device according to claim 1, wherein at least one of the wavelength conversion optical circuit units of the wavelength conversion device is located on one side of the connection lens optical path around the connection lens. A first wavelength conversion element is disposed, the second wavelength conversion element is disposed on the other side of the connection lens optical path, and the first wavelength conversion element and the second wavelength conversion element The signal light beam emitted from one of the wavelength conversion elements is configured to be incident on the other wavelength conversion element so as to pass through the connection lens and be condensed at a predetermined position of the other wavelength conversion element by the connection lens. The predetermined position of the other wavelength conversion element is a signal that has reached the arrival end portion between the incident end portion and the emission end portion of the wavelength conversion element body constituting the other wavelength conversion element. Light beam Alternatively, the reflector is arranged so that the signal light beam emitted from the reaching end is reflected by a reflector disposed at or near the reaching end and re-enters the same wavelength conversion element body. And when the re-incidence lens is not disposed in the optical path between the end of the other wavelength conversion element, the optical path length of the optical path through which the signal light beam passes between the entrance end and the exit end An incident end and an exit end of the wavelength conversion element main body that is at or near the condensing position that minimizes the volume of the signal light beam in the wavelength conversion element main body and that constitutes the other wavelength conversion element When neither the reflector nor the re-incidence lens is disposed between the portions, the volume of the signal light beam when viewed as the optical path length of the optical path through which the signal light beam passes between the incident end and the exit end To minimize When a reflector and a re-incidence lens are disposed in the optical path between the incident end and the exit end of the wavelength conversion element main body constituting the other wavelength conversion element at or near the condensing position Is to minimize the volume of the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between the incident end and the arrival end immediately before the re-incidence lens. A wavelength conversion device characterized by being at or near a condensing position.   5. The wavelength conversion device according to claim 4, wherein an incident light beam incident on the one wavelength conversion element is incident on the one wavelength conversion element so as to be condensed at a predetermined position of the one wavelength conversion element. The predetermined position of the one wavelength conversion element is at the arrival end between the incident end and the emission end of the wavelength conversion element main body constituting the one wavelength conversion element. The reflector is arranged to reflect the signal light beam that has arrived or the signal light beam emitted from the arrival end by a reflector disposed at or near the arrival end and re-enter the same wavelength conversion element body. Is the optical path length of the optical path through which the signal light beam passes between the incident end and the exit end when no re-incidence lens is disposed in the optical path between the reflector and the end of the one wavelength converting element. When I looked at The incident end and the exit end of the wavelength conversion element body constituting the one wavelength conversion element at or near the condensing position that minimizes the volume of the signal light beam in the wavelength conversion element body When the reflector and the re-incidence lens are not disposed between the input end and the output end, the volume of the signal light beam when viewed as the optical path length of the optical path through which the signal light beam passes is minimized. When the re-incident lens is disposed in the optical path between the incident end and the exit end of the wavelength conversion element main body constituting the one wavelength conversion element, which is at or near the condensing position In order to minimize the volume of the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between the incident end and the arrival end immediately before the re-incidence lens. Focusing position Properly the wavelength converter, characterized in that the in the vicinity.   6. The wavelength conversion device according to claim 4, wherein at least one wavelength conversion element includes at least one re-incidence lens, and the signal light beam passes through the re-incident lens and re-enters the wavelength conversion element. Is re-incident on the wavelength conversion element so as to be condensed at a predetermined position of the wavelength conversion element by the re-incident lens, and the predetermined position of the wavelength conversion element is Between the re-incidence lens of the wavelength conversion element main body and the emission end of the wavelength conversion element main body, the signal light beam reaching the arrival end or the signal light beam emitted from the arrival end is A reflector that is reflected by a reflector disposed at or near the arrival end and re-enters the same wavelength conversion element main body is disposed, but the reflector and the wavelength conversion element main body When no other re-incidence lens other than the re-incidence lens is arranged in the optical path, the signal between the re-incident end immediately after the re-incident lens and the output end of the wavelength conversion element body The wavelength conversion that constitutes the wavelength conversion element at or near the condensing position that minimizes the volume of the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the light beam passes If neither a reflector nor another re-incidence lens other than the re-incident lens is disposed between the re-incident lens of the element body and the exit end of the wavelength conversion element main body, immediately after the re-incident lens The wavelength conversion is at or near the condensing position that minimizes the volume of the signal light beam when viewed as the optical path length of the optical path through which the signal light beam passes between the re-incident end and the output end. Configure element When a re-incident lens other than the reflector and the re-incident lens is arranged in the optical path between the re-incident lens of the wavelength converting element main body and the exit end of the wavelength converting element main body The signal light in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between the re-incident end immediately after the re-incident lens and the arrival end immediately before the other re-incident lens A wavelength conversion device characterized by being at or near a condensing position that minimizes the volume of the beam.   The wavelength conversion device according to any one of claims 1 to 6, wherein the surface of the wavelength conversion element main body that is the incident end and the opposite surface thereof are formed in parallel with each other with an opening angle within one minute. A wavelength converter characterized by comprising:   8. The wavelength conversion device according to claim 1, wherein the wavelength conversion element body is a polarization reversal element having a polarization reversal region.   9. The wavelength conversion device according to claim 8, wherein the surface of the wavelength conversion element main body and the boundary surface of the domain-inverted region are formed in parallel with each other with an opening angle within 1 minute.   10. The wavelength conversion device according to claim 8, wherein boundary surfaces of the plurality of polarization inversion regions of the wavelength conversion element body are formed in parallel with each other with an opening angle of less than 1 minute. apparatus.   The wavelength conversion device according to any one of claims 8 to 10, wherein the width of the domain-inverted region of the wavelength conversion element body is in a direction orthogonal to an optical path of incident light first incident on the wavelength conversion element body, and A wavelength conversion device having a width of at least 2 mm in a plane including an optical path and an optical path of the next re-incident light.   12. The wavelength conversion device according to claim 8, wherein the polarization inversion element is PPLN (Periodically Polinated LiNbO 3), PPLT (Periodically Poled LiTaO 3), or PPKTP (Periodically Poled KTiOPO 4). apparatus.   13. The wavelength converter according to claim 1, wherein the reflector is a functional element that can transmit at least part of light having a specific wavelength.   14. The wavelength converter according to claim 13, wherein the reflectance of the reflector with respect to one or both of light having the first wavelength λ1 and light having the second wavelength λ2 is 99.8% or more. And a wavelength converter.   The wavelength conversion device according to claim 1, wherein there are a plurality of the connecting lenses.   16. The wavelength conversion device according to claim 1, further comprising means for changing at least one of a position of the connection lens on the optical path of the signal light beam and an angle with respect to the optical path. Conversion device.   17. The wavelength conversion device according to claim 1, wherein at least two of the re-incidence lenses are integrally formed.   The wavelength conversion device according to any one of claims 1 to 17, wherein a plurality of the connecting lenses are provided between two wavelength conversion elements.   The wavelength conversion device according to any one of claims 1 to 18, wherein at least one of the wavelength conversion optical circuit units of the wavelength conversion device is provided on one side of the connection lens constituting the wavelength conversion optical circuit unit. A signal, such as a reflector, in which the first wavelength conversion element and the second wavelength conversion element are arranged, and which can change the optical path of the signal light beam traveling in the connection lens optical path on the other side of the connection lens. An optical light path changing means is provided, and at least a part of the signal light beam passing through the connecting lens is bent by the signal light optical path changing means, and the optical path is changed between the first wavelength conversion element and the first wavelength conversion element. A wavelength conversion device, wherein a signal light beam emitted from one of the two wavelength conversion elements is folded so as to enter the other wavelength conversion element.   In the present invention, wavelength conversion is performed on light having a first wavelength λ1 included in incident light incident on a wavelength conversion element body, which will be described later, to light having a second wavelength λ2, which is a wavelength different from the first wavelength λ1. The element itself that can be used is called the wavelength conversion element body, the end of the wavelength conversion element body that makes incident light incident on the wavelength conversion element body is defined as the incident end, and the incident light enters the wavelength conversion element body. The wavelength converting element main body travels while undergoing wavelength conversion from the light having the first wavelength λ1 to the light having the second wavelength λ2, and includes light having the first wavelength λ1 and light having the second wavelength λ2. An end portion different from or near the end portion of the wavelength conversion element main body that reaches as light is defined as a reaching end portion of the wavelength conversion element main body, and the wavelength conversion is performed in the reaching end portion. The end that takes out the light that arrives and receives it as the outgoing light Defines the vicinity of the end as the exit end of the wavelength conversion element body, and the incident light including the light of the first wavelength λ1 before entering the wavelength conversion element body and the incident light enter the wavelength conversion element body The incident light including the light having the first wavelength λ1 and the light having the second wavelength λ2 that travels in the wavelength conversion element body while being subjected to wavelength conversion, and the incident light incident on the wavelength conversion element body are the wavelength conversion element. Each of the outgoing lights that have traveled through the body and have been subjected to wavelength conversion and emitted from the wavelength conversion element main body, or collectively referred to as signal light, an optical system or the like disposed in the wavelength conversion element main body, A wavelength conversion element body or the like mounted in a case is referred to as a wavelength conversion element. In a wavelength conversion device using at least one wavelength conversion element, an incident light beam incident on the wavelength conversion element is the wavelength Transformation element It is configured to enter the wavelength conversion element so as to be condensed at a predetermined position of the child, and the predetermined position of the wavelength conversion element is incident on the wavelength conversion element main body constituting the wavelength conversion element The same wavelength conversion is performed by reflecting the signal light beam reaching the arrival end or the signal light beam emitted from the arrival end between the end and the emission end with a reflector disposed at or near the arrival end. When the reflector to be re-incident on the element body is disposed, but a condenser lens (hereinafter also referred to as a re-incident lens) is not disposed on the optical path between the reflector and the end of the wavelength conversion element. Is a position corresponding to or near the midpoint of the total optical path length between the incident end and the output end, and between the incident end and the output end of the wavelength conversion element body constituting the wavelength conversion element. The reflector is also a re-incident lens If not disposed, the incident end of the wavelength conversion element main body constituting the wavelength conversion element is located at or near the midpoint of the total optical path length between the incident end and the emission end. When the reflector and the re-incidence lens are arranged in the optical path between the incident end and the exit end, it corresponds to the intermediate point of the total optical path length between the entrance end and the arrival end immediately before the re-incidence lens. A wavelength converter characterized by being at or near a position.   The wavelength conversion device according to claim 20, wherein the at least one wavelength conversion element has at least one re-incidence lens, and the signal light beam that re-enters the wavelength conversion element through the re-incident lens, The wavelength conversion element is configured to be re-incident on the wavelength conversion element so as to be condensed at a predetermined position of the wavelength conversion element by the re-incident lens, and the wavelength conversion element constitutes the wavelength conversion element. Between the re-incident lens of the wavelength conversion element body and the emission end of the wavelength conversion element body, the signal light beam reaching the arrival end or the signal light beam emitted from the arrival end is the arrival end. The reflector between the reflector and the wavelength conversion element main body is arranged so as to be reflected by the reflector arranged at or near the same portion and re-enter the same wavelength conversion element main body. If there is no other re-incident lens other than the re-incident lens, the total optical path length between the re-incident end immediately after the re-incident lens and the output end of the wavelength conversion element body is The reflector is also the re-incident lens between the re-incident lens of the wavelength conversion element main body constituting the wavelength conversion element and the exit end of the wavelength conversion element main body, which is at or near the position corresponding to the intermediate point. If no other re-incidence lens is disposed, the wavelength conversion element is located at or near the midpoint of the total optical path length between the re-incidence lens and the exit end. Another re-incidence lens different from the reflector and the re-incident lens in the optical path between the re-incident end immediately after the re-incident lens of the wavelength conversion element main body and the output end of the wavelength conversion element main body The re-incident Wavelength converter, characterized in that the position or the vicinity thereof corresponding to the midpoint of the total optical path length between the immediately preceding arrival end of the re-incident end portion and the other re-entering lenses immediately following lens.   The wavelength conversion device according to claim 20 or 21, wherein an incident light beam incident on the one wavelength conversion element is focused on the one wavelength conversion element so as to be condensed at a predetermined position of the one wavelength conversion element. The predetermined position of the one wavelength conversion element is configured to be incident between the incident end and the emission end of the wavelength conversion element main body constituting the one wavelength conversion element. The reflector is arranged to reflect the signal light beam reaching the part or the signal light beam emitted from the arrival end by a reflector disposed at or near the arrival end and re-enter the same wavelength conversion element body. However, when a re-incident lens is not arranged in the optical path between the reflector and the end of the one wavelength conversion element, the optical path of the signal light beam passes between the incident end and the output end. With optical path length The wavelength conversion element main body forming the one wavelength conversion element at or near the condensing position that minimizes the volume of the signal light beam in the wavelength conversion element main body when viewed When the reflector and the re-incidence lens are not arranged between the incident end and the exit end, the signal light beam when viewed as the optical path length of the optical path through which the signal light beam passes between the entrance end and the exit end The re-incident lens is disposed in the optical path between the incident end and the output end of the wavelength conversion element main body that constitutes the one wavelength conversion element that is at or near the condensing position that minimizes the volume of The volume of the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between the incident end and the arrival end just before the re-incidence lens. I will minimize it Wavelength converter, characterized in that such a condensing position or the vicinity thereof.   23. The wavelength conversion device according to claim 20, wherein at least one wavelength conversion element has at least one re-incidence lens, and re-enters the wavelength conversion element through the re-incident lens. The signal light beam is configured to re-enter the wavelength conversion element so that the signal light beam is condensed at the predetermined position of the wavelength conversion element by the re-incidence lens, and the predetermined position of the wavelength conversion element is Between the re-incident lens of the wavelength conversion element main body constituting the wavelength conversion element and the emission end of the wavelength conversion element main body, the signal light beam reaching the arrival end or the signal light emitted from the arrival end A reflector that reflects the beam with a reflector disposed at or near the reaching end and re-enters the same wavelength conversion element main body is disposed. When another re-incident lens other than the re-incident lens is not disposed in the optical path between the child main bodies, the re-incident end immediately after the re-incident lens and the output end of the wavelength conversion element main body The wavelength conversion element is located at or near the condensing position that minimizes the volume of the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes. If neither a reflector nor another re-incidence lens other than the re-incidence lens is disposed between the re-incidence lens of the wavelength conversion element main body and the exit end of the wavelength conversion element main body, A condensing position at or near the condensing position that minimizes the volume of the signal light beam when viewed as the optical path length of the optical path through which the signal light beam passes between the re-incidence end and the exit end immediately after the incident lens. , The wavelength conversion Another re-incident lens other than the reflector and the re-incident lens is disposed in the optical path between the re-incident lens of the wavelength conversion element main body constituting the optical element and the emission end of the wavelength conversion element main body. In the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between the re-incident end immediately after the re-incident lens and the arrival end immediately before the other re-incident lens. A wavelength conversion device characterized by being at or near the light condensing position that minimizes the volume of the signal light beam.   The wavelength conversion device according to any one of claims 20 to 23, wherein a surface that becomes the incident end of the wavelength conversion element body and a surface opposite to the surface are formed in parallel with each other with an opening angle of within 1 minute. A wavelength converter characterized by comprising:   25. The wavelength conversion device according to claim 20, wherein the wavelength conversion element body is a polarization reversal element having a polarization reversal region.   26. The wavelength conversion device according to claim 25, wherein a surface of the wavelength conversion element body and a boundary surface of the domain-inverted region are formed in parallel with each other with an opening angle of 1 minute or less.   27. The wavelength conversion device according to claim 25, wherein boundary surfaces of a plurality of polarization inversion regions of the wavelength conversion element body are formed in parallel with each other with an opening angle of less than 1 minute. apparatus.   28. The wavelength conversion device according to claim 25, wherein a width of a polarization inversion region of the wavelength conversion element body is in a direction orthogonal to an optical path of incident light first incident on the wavelength conversion element body, and A wavelength conversion device having a width of at least 2 mm in a plane including an optical path and an optical path of the next re-incident light.   29. The wavelength conversion device according to claim 25, wherein the polarization inverting element is PPLN (Periodically Poled LiNbO3), PPLT (Periodically Poled LiTaO3), or PPKTP (Periodically Poled KTiOPO4). apparatus.   30. The wavelength converter according to any one of claims 20 to 29, wherein the reflector is a functional element capable of transmitting at least part of light having a specific wavelength.   31. The wavelength converter according to claim 30, wherein the reflectance of the reflector with respect to one or both of the light with the first wavelength λ1 and the light with the second wavelength λ2 is 99.8% or more. And a wavelength converter.   32. The wavelength conversion device according to claim 20, wherein at least two of the re-incidence lenses are integrally formed.   33. The wavelength conversion device according to claim 20, further comprising means for changing at least one of a position of the connection lens on the optical path of the signal light beam and an angle with respect to the optical path. Conversion device.   In the present invention, wavelength conversion is performed on light having a first wavelength λ1 included in incident light incident on a wavelength conversion element body, which will be described later, to light having a second wavelength λ2, which is a wavelength different from the first wavelength λ1. The element itself that can be used is called the wavelength conversion element body, the end of the wavelength conversion element body that makes incident light incident on the wavelength conversion element body is defined as the incident end, and the incident light enters the wavelength conversion element body. The wavelength converting element main body travels while undergoing wavelength conversion from the light having the first wavelength λ1 to the light having the second wavelength λ2, and includes light having the first wavelength λ1 and light having the second wavelength λ2. An end portion different from or near the end portion of the wavelength conversion element main body that reaches as light is defined as a reaching end portion of the wavelength conversion element main body, and the wavelength conversion is performed in the reaching end portion. The end that takes out the light that arrives and receives it as the outgoing light Defines the vicinity of the end as the exit end of the wavelength conversion element body, and the incident light including the light of the first wavelength λ1 before entering the wavelength conversion element body and the incident light enter the wavelength conversion element body The incident light including the light having the first wavelength λ1 and the light having the second wavelength λ2 that travels in the wavelength conversion element body while being subjected to wavelength conversion, and the incident light incident on the wavelength conversion element body are the wavelength conversion element. Each of the outgoing lights that have traveled through the body and have been subjected to wavelength conversion and emitted from the wavelength conversion element main body, or collectively referred to as signal light, an optical system or the like disposed in the wavelength conversion element main body, A wavelength conversion device in which a wavelength conversion device main body or the like is mounted in a case or the like is referred to as a wavelength conversion device, and in the wavelength conversion device using at least two of the wavelength conversion devices, the wavelength conversion device is a signal light beam subjected to wavelength conversion In the light path And having at least one wavelength conversion optical circuit unit having at least two wavelength conversion elements connected in series via a lens (hereinafter also referred to as a connecting lens), and at least one of the wavelength conversion devices The wavelength conversion optical circuit section includes an emission end of one wavelength conversion element (hereinafter also referred to as a first wavelength conversion element) of two wavelength conversion elements connected in series via the connection lens. An optical path of a signal light beam including an optical path passing through the connection lens between incident ends of the other wavelength conversion element (hereinafter also referred to as a second wavelength conversion element) is also referred to as a connection lens optical path. The signal light beam emitted from the wavelength conversion element enters the second wavelength conversion element so that it passes through the connection lens optical path and is condensed by the connection lens at a predetermined position of the second wavelength conversion element. The predetermined position of the second wavelength conversion element reaches between the incident end and the emission end of the wavelength conversion element main body constituting the second wavelength conversion element. The reflector is arranged to reflect the signal light beam reaching the end or the signal light beam emitted from the reaching end by a reflector disposed at or near the reaching end and re-enter the same wavelength conversion element body. However, when a condenser lens (hereinafter also referred to as a re-incident lens) is not disposed in the optical path between the reflector and the end of the second wavelength conversion element, the incident end and the exit end The second wavelength conversion is at or near the condensing position that minimizes the volume of the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes. Make up element When neither the reflector nor the re-incidence lens is arranged between the incident end and the exit end of the wavelength conversion element body, the optical path length of the optical path through which the signal light beam passes between the entrance end and the exit end The wavelength conversion element main body constituting the second wavelength conversion element at or near the condensing position that minimizes the volume of the signal light beam in the wavelength conversion element main body When the re-incident lens is disposed in the optical path between the light-emitting portion and the exit end portion, the optical path length of the optical path through which the signal light beam passes between the incident end portion and the arrival end portion immediately before the re-incident lens is viewed. A wavelength conversion device characterized by being at or near a condensing position that minimizes the volume of the signal light beam in the wavelength conversion element body.   35. The wavelength conversion device according to claim 34, wherein an incident light beam incident on the first wavelength conversion element is incident on the one wavelength conversion element so as to be condensed at a predetermined position of the one wavelength conversion element. The predetermined position of the one wavelength conversion element is between the incident end and the output end of the wavelength conversion element main body constituting the one wavelength conversion element, and the reaching end The reflector is arranged to reflect the signal light beam that has arrived at or the signal light beam emitted from the arrival end by a reflector disposed at or near the arrival end and re-enter the same wavelength conversion element body. However, when a re-incident lens is not disposed in the optical path between the reflector and the end of the one wavelength conversion element, the optical path of the optical path through which the signal light beam passes between the incident end and the output end As long as In the wavelength conversion element main body of the wavelength conversion element main body, which is at or near the condensing position that minimizes the volume of the signal light beam, and that constitutes the one wavelength conversion element, In the case where neither the reflector nor the re-incidence lens is arranged between the portions, the wavelength conversion element body in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between the entrance end and the exit end Re-enter the optical path between the incident end and the output end of the wavelength conversion element body that is at or near the condensing position that minimizes the volume of the signal light beam. When a lens is disposed, the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between the incident end and the arrival end immediately before the re-incidence lens Body of Wavelength converter, characterized in that the a focusing position or in the vicinity thereof so as to minimize.   36. The wavelength conversion device according to claim 34 or 35, wherein at least one wavelength conversion element has at least one re-incident lens, and passes through the re-incident lens and re-enters the wavelength conversion element. Is re-incident on the wavelength conversion element so as to be condensed at a predetermined position of the wavelength conversion element by the re-incident lens, and the predetermined position of the wavelength conversion element is Between the re-incident lens of the wavelength conversion element main body and the emission end of the wavelength conversion element main body constituting the signal light beam reaching the arrival end or the signal light beam emitted from the arrival end A reflector that is reflected by a reflector disposed at or near the arrival end and re-enters the same wavelength conversion element main body is disposed, but the reflector and the wavelength conversion element book If no other re-incidence lens other than the re-incidence lens is arranged in the optical path between the re-incident end immediately after the re-incident lens and the emission end of the wavelength conversion element body The wavelength conversion element constitutes the wavelength conversion element at or near the condensing position that minimizes the volume of the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes. When neither a reflector nor another re-incident lens other than the re-incident lens is disposed between the re-incident lens of the wavelength conversion element main body and the exit end of the wavelength conversion element main body, the re-incident lens Or a condensing position that minimizes the volume of the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between the re-incident end and the output end immediately after Its neighborhood Yes, another re-incidence of the reflector and the re-incidence lens in the optical path between the re-incidence lens of the wavelength conversion element body constituting the wavelength conversion element and the emission end of the wavelength conversion element body When the lens is arranged, the optical path length of the optical path through which the signal light beam passes between the re-incident end immediately after the re-incident lens and the arrival end immediately before the other re-incident lens A wavelength conversion device characterized by being at or near a condensing position that minimizes the volume of the signal light beam in the wavelength conversion element body.   37. The wavelength conversion device according to claim 34, wherein a surface serving as the incident end of the wavelength conversion element body and a surface opposite to the surface are formed in parallel with each other with an opening angle of within one minute. A wavelength converter characterized by comprising:   38. The wavelength conversion device according to claim 34, wherein the wavelength conversion element body is a polarization reversal element having a polarization reversal region.   39. The wavelength conversion device according to claim 38, wherein the surface of the wavelength conversion element main body and the boundary surface of the domain-inverted region are formed in parallel with each other with an opening angle of 1 minute or less.   40. The wavelength conversion device according to claim 38 or 39, wherein boundary surfaces of the plurality of polarization inversion regions of the wavelength conversion element body are formed in parallel with each other with an opening angle of 1 minute or less. apparatus.   41. The wavelength conversion device according to claim 38, wherein a width of a polarization inversion region of the wavelength conversion element body is in a direction orthogonal to an optical path of incident light first incident on the wavelength conversion element body, and A wavelength conversion device having a width of at least 2 mm in a plane including an optical path and an optical path of the next re-incident light.   The wavelength conversion device according to any one of claims 38 to 41, wherein the polarization inverting element is PPLN (Periodically Poled LiNbO3), PPLT (Periodically Poled LiTaO3), or PPKTP (Periodically Poled KTiOPO4). apparatus.   43. The wavelength converter according to claim 34, wherein the reflector is a functional element that can transmit at least part of light of a specific wavelength.   44. The wavelength conversion device according to claim 43, wherein the reflectance of the reflector with respect to one or both of light having the first wavelength λ1 and light having the second wavelength λ2 is 99.8% or more. And a wavelength converter.   45. The wavelength converter according to claim 34, wherein at least two of the re-incidence lenses are integrally formed.   46. The wavelength conversion device according to claim 34, wherein a plurality of the connecting lenses are provided between two wavelength conversion elements.   47. The wavelength conversion device according to claim 34, further comprising means for changing at least one of a position of the connection lens on the optical path of the signal light beam and an angle with respect to the optical path. Conversion device.   48. The wavelength conversion device according to claim 34, wherein at least one of the wavelength conversion optical circuit units of the wavelength conversion device is provided on one side of the connection lens constituting the wavelength conversion optical circuit unit. A signal, such as a reflector, in which the first wavelength conversion element and the second wavelength conversion element are arranged, and which can change the optical path of the signal light beam traveling in the connection lens optical path on the other side of the connection lens. An optical light path changing means is provided, and at least a part of the signal light beam passing through the connecting lens is bent by the signal light optical path changing means, and the optical path is changed between the first wavelength conversion element and the first wavelength conversion element. A wavelength conversion device, wherein a signal light beam emitted from one of the two wavelength conversion elements is folded so as to enter the other wavelength conversion element.   In the present invention, wavelength conversion is performed on light having a first wavelength λ1 included in incident light incident on a wavelength conversion element body, which will be described later, to light having a second wavelength λ2, which is a wavelength different from the first wavelength λ1. The element itself that can be used is called the wavelength conversion element body, the end of the wavelength conversion element body that makes incident light incident on the wavelength conversion element body is defined as the incident end, and the incident light enters the wavelength conversion element body. The wavelength converting element main body travels while undergoing wavelength conversion from the light having the first wavelength λ1 to the light having the second wavelength λ2, and includes light having the first wavelength λ1 and light having the second wavelength λ2. An end portion different from or near the end portion of the wavelength conversion element main body that reaches as light is defined as a reaching end portion of the wavelength conversion element main body, and the wavelength conversion is performed in the reaching end portion. The end that takes out the light that arrives and receives it as the outgoing light Defines the vicinity of the end as the exit end of the wavelength conversion element body, and the incident light including the light of the first wavelength λ1 before entering the wavelength conversion element body and the incident light enter the wavelength conversion element body The incident light including the light having the first wavelength λ1 and the light having the second wavelength λ2 that travels in the wavelength conversion element body while being subjected to wavelength conversion, and the incident light incident on the wavelength conversion element body are the wavelength conversion element. Each of the outgoing lights that have traveled through the body and have been subjected to wavelength conversion and emitted from the wavelength conversion element main body, or collectively referred to as signal light, an optical system or the like disposed in the wavelength conversion element main body, A wavelength conversion element body or the like mounted in a case is referred to as a wavelength conversion element. In a wavelength conversion device using at least one wavelength conversion element, an incident light beam incident on the wavelength conversion element is the wavelength Transformation element It is configured to enter the wavelength conversion element so as to be condensed at a predetermined position of the child, and the predetermined position of the wavelength conversion element is incident on the wavelength conversion element main body constituting the wavelength conversion element The same wavelength conversion is performed by reflecting the signal light beam reaching the arrival end or the signal light beam emitted from the arrival end between the end and the emission end with a reflector disposed at or near the arrival end. When the reflector to be re-incident on the element body is disposed, but a condenser lens (hereinafter also referred to as a re-incident lens) is not disposed on the optical path between the reflector and the end of the wavelength conversion element. Is at or near the condensing position that minimizes the volume of the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between the input end and the output end. Yes, before When neither the reflector nor the re-incidence lens is disposed between the incident end and the exit end of the wavelength conversion element main body constituting the wavelength conversion element, the signal is transmitted between the entrance end and the exit end. The wavelength conversion that constitutes the wavelength conversion element at or near the condensing position that minimizes the volume of the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the light beam passes When a re-incident lens is disposed in the optical path between the incident end and the outgoing end of the element body, the optical path through which the signal light beam passes between the incident end and the arrival end immediately before the re-incident lens A wavelength conversion device characterized in that it is at or near the condensing position that minimizes the volume of the signal light beam in the wavelength conversion element main body when viewed as the optical path length.   The wavelength conversion device according to claim 49, wherein at least one wavelength conversion element has at least one re-incidence lens, and the signal light beam that re-enters the wavelength conversion element through the re-incident lens, The wavelength conversion element is configured to be re-incident on the wavelength conversion element so as to be condensed at a predetermined position of the wavelength conversion element by the re-incident lens, and the wavelength conversion element constitutes the wavelength conversion element. Between the re-incident lens of the wavelength conversion element body and the emission end of the wavelength conversion element body, the signal light beam reaching the arrival end or the signal light beam emitted from the arrival end is the arrival end. The reflector between the reflector and the wavelength conversion element main body is arranged so as to be reflected by the reflector arranged at or near the same portion and re-enter the same wavelength conversion element main body. If no other re-incidence lens is disposed on the wavelength conversion element body, the optical path length of the optical path through which the signal light beam passes between the incident end and the exit end is determined. A re-incidence end immediately after the re-incidence lens of the wavelength conversion element main body constituting the wavelength conversion element and the wavelength thereof at or near the condensing position that minimizes the volume of the signal light beam at When neither a reflector nor another re-incidence lens other than the re-incidence lens is arranged between the exit end of the conversion element body, it is between the re-incidence end immediately after the re-incident lens and the exit end. In the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes, it is at or near the condensing position that minimizes the volume of the signal light beam, and constitutes the wavelength conversion element. Wavelength conversion element When another re-incident lens other than the reflector and the re-incident lens is disposed in the optical path between the re-incident lens of the main body and the emission end of the wavelength conversion element main body, The volume of the signal light beam in the wavelength conversion element body is minimized when viewed as the optical path length of the optical path through which the signal light beam passes between the re-incident end immediately after and the arrival end immediately before the other re-incidence lens. A wavelength conversion device characterized by being at or near the condensing position.   The wavelength conversion device according to claim 49 or 50, wherein the surface that becomes the incident end of the wavelength conversion element body and the surface on the opposite side thereof are formed in parallel with each other with an opening angle of within one minute. A featured wavelength converter.   52. The wavelength conversion device according to claim 49, wherein the wavelength conversion element body is a polarization reversal element having a polarization reversal region.   53. The wavelength conversion device according to claim 52, wherein a surface of the wavelength conversion element body and a boundary surface of the domain-inverted region are formed in parallel with each other with an opening angle within 1 minute.   54. The wavelength conversion device according to claim 52, wherein boundary surfaces of a plurality of polarization inversion regions of the wavelength conversion element body are formed in parallel with each other with an opening angle of less than 1 minute. apparatus.   The wavelength conversion device according to any one of claims 52 to 54, wherein a width of a polarization inversion region of the wavelength conversion element main body is in a direction orthogonal to an optical path of incident light first incident on the wavelength conversion element main body, and A wavelength conversion device characterized in that the width in the plane including the optical path and the optical path of the next re-incident light is at least 2 mm.   The wavelength conversion device according to any one of claims 52 to 55, wherein the polarization inverting element is PPLN (Periodically Poled LiNbO3), PPLT (Periodically Poled LiTaO3) or PPKTP (Periodically Poled KTiOPO4). apparatus.   57. The wavelength conversion device according to claim 49, wherein at least two of the re-incidence lenses are integrally formed.   The wavelength converter according to any one of claims 49 to 57, further comprising means for changing at least one of a position of the connecting lens and an angle with respect to the optical path on the optical path of the signal light beam. Conversion device.   In the present invention, wavelength conversion is performed on light having a first wavelength λ1 included in incident light incident on a wavelength conversion element body, which will be described later, to light having a second wavelength λ2, which is a wavelength different from the first wavelength λ1. The element itself that can be used is called the wavelength conversion element body, the end of the wavelength conversion element body that makes incident light incident on the wavelength conversion element body is defined as the incident end, and the incident light enters the wavelength conversion element body. The wavelength converting element main body travels while undergoing wavelength conversion from the light having the first wavelength λ1 to the light having the second wavelength λ2, and includes light having the first wavelength λ1 and light having the second wavelength λ2. An end portion different from or near the end portion of the wavelength conversion element main body that reaches as light is defined as a reaching end portion of the wavelength conversion element main body, and the wavelength conversion is performed in the reaching end portion. The end that takes out the light that arrives and receives it as the outgoing light Defines the vicinity of the end as the exit end of the wavelength conversion element body, and the incident light including the light of the first wavelength λ1 before entering the wavelength conversion element body and the incident light enter the wavelength conversion element body The incident light including the light having the first wavelength λ1 and the light having the second wavelength λ2 that travels in the wavelength conversion element body while being subjected to wavelength conversion, and the incident light incident on the wavelength conversion element body are the wavelength conversion element. Each of the outgoing lights that have traveled through the body and have been subjected to wavelength conversion and emitted from the wavelength conversion element main body, or collectively referred to as signal light, an optical system or the like disposed in the wavelength conversion element main body, A wavelength conversion element in which a wavelength conversion element main body or the like is mounted in a case or the like is referred to as a wavelength conversion element, and the wavelength conversion method converts the wavelength of signal light using at least two of the wavelength conversion elements. Given At least two wavelength conversion elements connected in series via a lens (hereinafter also referred to as a connecting lens) in the optical path of the signal light beam, and the two connected in series via the connecting lens Of the wavelength conversion elements, one of the wavelength conversion elements (hereinafter also referred to as a first wavelength conversion element) and the other end of the wavelength conversion element (hereinafter also referred to as a second wavelength conversion element). The optical path of the signal light beam including the optical path passing through the connecting lens in between is also referred to as a connecting lens optical path, and the first wavelength is placed on one side of the connecting lens optical path across the intermediate point of the connecting lens optical path. A conversion element is disposed, the second wavelength conversion element is disposed on the other side of the connection lens optical path, and the signal light beam emitted from the first wavelength conversion element passes through the connection lens to the connection lens. The second wavelength conversion element is configured to be incident on the second wavelength conversion element so as to be condensed at a predetermined position of the second wavelength conversion element, and the predetermined position of the second wavelength conversion element is the second wavelength conversion element. The signal light beam reaching the arrival end or the signal light beam emitted from the arrival end between the incident end and the emission end of the wavelength conversion element body constituting the wavelength conversion element Alternatively, the reflector that is reflected by the reflector disposed in the vicinity thereof and re-enters the same wavelength conversion element main body is disposed, but is collected in the optical path between the reflector and the end of the second wavelength conversion element. When an optical lens (hereinafter also referred to as a re-incident lens) is not disposed, the signal light is positioned so as to be at or near the midpoint of the total optical path length between the entrance end and the exit end. Wavelength is converted, and the second wavelength conversion element is In the case where neither the reflector nor the re-incidence lens is arranged between the incident end and the exit end of the wavelength conversion element body formed, the intermediate point of the total optical path length between the entrance end and the exit end The wavelength of the signal light is converted so that the position corresponds to or near the position, and the optical path between the incident end and the output end of the wavelength conversion element body constituting the second wavelength conversion element When the reflector and the re-incidence lens are arranged, the signal is positioned so as to be at or near the midpoint of the total optical path length between the incident end and the arrival end immediately before the re-incidence lens. A wavelength conversion method characterized by converting the wavelength of light.   The wavelength conversion method according to claim 59, wherein the at least one wavelength conversion element has at least one re-incidence lens, and the signal light beam that re-enters the wavelength conversion element through the re-incidence lens, The wavelength conversion element is configured to be re-incident on the wavelength conversion element so that the light is focused on the wavelength conversion element at a predetermined position by the re-incident lens, and the wavelength conversion element constitutes the wavelength conversion element. Between the re-incident lens of the wavelength conversion element body and the emission end of the wavelength conversion element body, the signal light beam reaching the arrival end or the signal light beam emitted from the arrival end is the arrival end. The reflector between the reflector and the wavelength conversion element main body is arranged so as to be reflected by the reflector arranged at or near the same portion and re-enter the same wavelength conversion element main body. If there is no other re-incident lens other than the re-incident lens, the total optical path length between the re-incident end immediately after the re-incident lens and the output end of the wavelength conversion element body is The wavelength of the signal light is converted so as to be at or near the position corresponding to the intermediate point, and the re-incident lens of the wavelength conversion element body constituting the wavelength conversion element and the emission end of the wavelength conversion element body If no reflector or another re-incidence lens other than the re-incidence lens is disposed between the re-incidence lens and the re-incidence end portion immediately after the re-incidence lens, the middle of the total optical path length between the exit end portion The wavelength of the signal light is converted so that it is at or near the position corresponding to the point, and the re-incidence lens of the wavelength conversion element body constituting the wavelength conversion element and the emission end of the wavelength conversion element body Reflector and the re-incident lens in the optical path between In the case where another re-incidence lens is arranged, the intermediate point of the total optical path length between the re-incident end immediately after the re-incident lens and the arrival end immediately before the other re-incident lens A wavelength conversion method characterized by converting the wavelength of the signal light so as to be in a position corresponding to or near the position.   61. The wavelength conversion method according to claim 59, wherein a polarization reversal element having a polarization reversal region is used in the wavelength conversion element body.   In the present invention, wavelength conversion is performed on light having a first wavelength λ1 included in incident light incident on a wavelength conversion element body, which will be described later, to light having a second wavelength λ2, which is a wavelength different from the first wavelength λ1. The element itself that can be used is called the wavelength conversion element body, the end of the wavelength conversion element body that makes incident light incident on the wavelength conversion element body is defined as the incident end, and the incident light enters the wavelength conversion element body. The wavelength converting element main body travels while undergoing wavelength conversion from the light having the first wavelength λ1 to the light having the second wavelength λ2, and includes light having the first wavelength λ1 and light having the second wavelength λ2. An end portion different from or near the end portion of the wavelength conversion element main body that reaches as light is defined as a reaching end portion of the wavelength conversion element main body, and the wavelength conversion is performed in the reaching end portion. The end that takes out the light that arrives and receives it as the outgoing light Defines the vicinity of the end as the exit end of the wavelength conversion element body, and the incident light including the light of the first wavelength λ1 before entering the wavelength conversion element body and the incident light enter the wavelength conversion element body The incident light including the light having the first wavelength λ1 and the light having the second wavelength λ2 that travels in the wavelength conversion element body while being subjected to wavelength conversion, and the incident light incident on the wavelength conversion element body are the wavelength conversion element. Each of the outgoing lights that have traveled through the body and have been subjected to wavelength conversion and emitted from the wavelength conversion element main body, or collectively referred to as signal light, an optical system or the like disposed in the wavelength conversion element main body, A wavelength conversion element in which a wavelength conversion element main body or the like is mounted in a case or the like is referred to as a wavelength conversion element, and the wavelength conversion method converts the wavelength of signal light using at least two of the wavelength conversion elements. Given At least two wavelength conversion elements connected in series via a lens (hereinafter also referred to as a connecting lens) in the optical path of the signal light beam, and the two connected in series via the connecting lens Of the wavelength conversion elements, one of the wavelength conversion elements (hereinafter also referred to as a first wavelength conversion element) and the other end of the wavelength conversion element (hereinafter also referred to as a second wavelength conversion element). The optical path of the signal light beam including the optical path passing through the connecting lens in between is also referred to as a connecting lens optical path, and the first wavelength is placed on one side of the connecting lens optical path across the intermediate point of the connecting lens optical path. A conversion element is disposed, the second wavelength conversion element is disposed on the other side of the connection lens optical path, and the signal light beam emitted from the first wavelength conversion element passes through the connection lens to the connection lens. Then, the light is incident on the second wavelength conversion element so as to be condensed at a predetermined position of the second wavelength conversion element, and the predetermined position of the second wavelength conversion element is the second wavelength conversion element. The signal light beam reaching the arrival end or the signal light beam emitted from the arrival end between the incident end and the emission end of the wavelength conversion element main body constituting the The reflector that is reflected by the disposed reflector and re-enters the same wavelength conversion element main body is disposed, but a condensing lens (hereinafter referred to as an optical path) between the reflector and the end of the second wavelength conversion element is disposed. (Also referred to as a re-incidence lens) is not disposed, the signal light beam in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between the entrance end and the exit end Condensation that minimizes volume The wavelength of the signal light is converted so as to be in the vicinity thereof or in the vicinity thereof, and the reflector is also reincident between the incident end and the emission end of the wavelength conversion element main body constituting the second wavelength conversion element. When no lens is arranged, the volume of the signal light beam in the wavelength conversion element body is minimized when viewed as the optical path length of the optical path through which the signal light beam passes between the incident end and the output end. The wavelength of the signal light is converted so as to be at or near the light condensing position, and re-entered in the optical path between the incident end and the output end of the wavelength conversion element body constituting the second wavelength conversion element. When an incident lens is disposed, the signal light in the wavelength conversion element body when viewed as the optical path length of the optical path through which the signal light beam passes between the incident end and the arrival end immediately before the re-incidence lens Minimize the volume of the beam A wavelength conversion method characterized by converting the wavelength of signal light so as to be at or near such a condensing position.   63. The wavelength conversion method according to claim 62, wherein at least one wavelength conversion element has at least one re-incident lens, and the signal light beam that re-enters the wavelength conversion element through the re-incident lens, The wavelength conversion element is configured to be re-incident on the wavelength conversion element so that the light is focused on the wavelength conversion element at a predetermined position by the re-incident lens, and the wavelength conversion element constitutes the wavelength conversion element. Between the re-incident lens of the wavelength conversion element body and the emission end of the wavelength conversion element body, the signal light beam reaching the arrival end or the signal light beam emitted from the arrival end is the arrival end. The reflector between the reflector and the wavelength conversion element main body is arranged so as to be reflected by the reflector arranged at or near the same portion and re-enter the same wavelength conversion element main body. If no other re-incidence lens other than the re-incidence lens is disposed, the signal light beam is between the re-incidence end immediately after the re-incidence lens and the emission end of the wavelength conversion element body. The wavelength of the signal light is converted so that the volume of the signal light beam within the wavelength conversion element body is at or near the condensing position when viewed as the optical path length of the optical path that passes through the wavelength conversion element. When neither a reflector nor another re-incidence lens other than the re-incident lens is arranged between the re-incident lens of the wavelength conversion element main body constituting the element and the exit end of the wavelength conversion element main body The volume of the signal light beam in the wavelength conversion element body is minimized when viewed as the optical path length of the optical path through which the signal light beam passes between the re-incidence end and the exit end immediately after the re-incidence lens. Condensing like The wavelength of the signal light is converted so as to be in the vicinity thereof or in the vicinity thereof, in the optical path between the re-incident lens of the wavelength conversion element body constituting the wavelength conversion element and the emission end of the wavelength conversion element body When another re-incidence lens other than the reflector and the re-incidence lens is arranged, between the re-incidence end immediately after the re-incidence lens and the arrival end just before the other re-incidence lens The wavelength of the signal light so that the volume of the signal light beam in the wavelength conversion element body is at or near the condensing position when viewed as the optical path length of the optical path through which the signal light beam passes. The wavelength conversion method characterized by converting.   64. The wavelength conversion method according to claim 62, wherein the wavelength conversion method is a polarization reversal element having a polarization reversal region in the wavelength conversion element body. In the present invention, the element that can convert the wavelength of the first wavelength λ1 included in the incident light into the light of the second wavelength λ2 that is different from the first wavelength λ1 is called a wavelength conversion element. In particular, the end of the wavelength conversion element that causes the incident light to enter the wavelength conversion element is defined as the incident end, and the incident light enters the wavelength conversion element and the light from the first wavelength λ1 enters the wavelength conversion element. What is the incident end of the wavelength conversion element that travels while undergoing wavelength conversion to light of the second wavelength λ2 and arrives as light including light of the first wavelength λ1 and light of the second wavelength λ2? A different end portion or the vicinity of the end portion is defined as a reaching end portion of the wavelength conversion element, and the end portion or the vicinity of the end portion that takes out the light that has reached the wavelength conversion in the reaching end portion as outgoing light. Is defined as the output end of the wavelength conversion element, and the wavelength conversion element The incident light including the light of the first wavelength λ1 before being incident, the light of the first wavelength λ1 traveling through the wavelength conversion element while the incident light is incident on the wavelength conversion element and undergoes wavelength conversion, and the second light The incident light including the light of wavelength λ2 and the incident light incident on the wavelength conversion element travel through the wavelength conversion element and are subjected to wavelength conversion, respectively, or emitted light emitted from the wavelength conversion element, or a general term for them. In the wavelength conversion element, the wavelength conversion element has at least one arrival end portion different from the incident end portion and the emission end portion, and is located at or near the arrival end portion. A reflector that acts to reflect at least the light of the first wavelength λ1 as the signal light that has reached the light, and to proceed while undergoing wavelength conversion to the light of the second wavelength λ2 in the wavelength conversion element Is arranged and said As the long conversion element, a polarization inversion element having a polarization inversion region is used. Condition 1 is that the incident surface of the wavelength conversion element and the boundary surface of the polarization inversion region are formed in parallel with each other with an opening angle of less than 1 minute. Condition 2 is that the output surface of the wavelength conversion element and the boundary surface of the domain-inverted region are formed in parallel with each other with an opening angle within 1 minute, and Condition 3 is that a plurality of domain-inverted It is assumed that the boundary surfaces of the regions are formed in parallel with each other with an opening angle of 1 minute or less. Condition 4 is that the width of the domain-inverted region is equal to the optical path of the incident light first incident on the wavelength conversion element. It is assumed that the width in the plane including the optical path and the optical path of the next re-incident light is at least 2 mm in the orthogonal direction, and condition 5 is that the surface that becomes the incident end of the wavelength conversion element and the surface opposite to the surface With an opening angle within 1 minute And it is formed in parallel to have the wavelength conversion element is the wavelength conversion element characterized in that it meets at least two of said condition 1-5.

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