JP2004334169A - Beam multiplexing element, beam multiplexing method, beam separating element, beam separating method, and exciting light output device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact beam multiplexing element capable of realizing high-luminance output, and an exciting light output device using the same. <P>SOLUTION: The beam multiplexing element is constituted at least of a birefringence material part 1 and a phase difference part 2 arranged at least at a part of the beam incident end face 1A of the material part 1. Then, 1st and 2nd beams Li1 and Li2 (beam group in the case of making a plurality of beams incident) whose propagating directions are nearly parallel and which are made nearly the same polarized light are made incident on the material part 1, and at least either beam Li1 out of the 1st and the 2nd beams is made incident on the material part 1 via the phase difference part 2 so as to change a polarization direction by the phase difference part 2, and the propagating direction of at least either beam out of the 1st and the 2nd beams Li1 and Li2 in the material part 1 is changed, so that the 1st and the 2nd beams are multiplexed at the emitting position of the material part 1 and emitted in nearly the same direction. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a beam combining element, a beam combining method, a beam separating element, a beam separating method, and a pumping light output device that combine or separate a plurality of light beams and use, for example, outgoing light as an excitation light source.

There is an increasing demand for a fiber output pump light source that is very easy to use practically because the output position and the output direction of the light source can be freely set by using the output light of a semiconductor laser diode (LD). The fiber output pumping light source, also called a pigtail laser, that emits the light emitted from an LD through a fiber is used in the optical communication field, as well as in industrial, medical, printing, and other industries such as processing and inspection and laser excitation. And various fields.
As such a light source, as the output and the luminance are larger, and as the light source is smaller, the usable applications are expanded.
Further, even when a fiber is not used for the light emitting method, if the light source itself is small and has high brightness, the range in which the light source can be installed, and the application field is widened.

  In order to increase the output and the brightness of the light source, if the input current to the LD is increased, reliability is sacrificed. Therefore, it is convenient to combine a plurality of the same LD light sources. In order to reduce the size, it is desirable to reduce the number of internal parts of the light source device as much as possible and to make precision adjustment as unnecessary as possible.

For example, a polarization beam splitter (PBS) is often used for beam combining of two LD output lights (for example, see Patent Document 1).
Patent Literature 1 proposes a device that is installed in a direction orthogonal to the emission direction of an LD, and that combines and combines the polarization planes using PBS.

However, in order to increase the multiplexing efficiency by using the PBS in this way, for two beams having polarizations orthogonal to each other, the beam direction and the overlap at the beam multiplexing portion must be sufficiently large. In addition, since the allowable angle of incidence of the PBS is generally small, precise optical adjustment is required.
Further, when using a PBS, it is necessary to make the beam direction incident on the PBS different. For example, when a cubic PBS is used as described in Patent Document 1, the incident directions are orthogonal to each other. Therefore, when an LD in which electrodes and cooling elements are individually arranged is arranged, it is difficult to reduce the size of the multiplexing element.

  In addition, even when an integrated LD light source in which LD elements are arranged close to each other is used, such as a so-called array type LD in which a large number of LDs are arranged, a folding mirror for changing a beam emission direction and precise adjustment of the arrangement are required. Required. In addition, in the case of using the folding mirror as described above, since the optical path lengths are different, there is a disadvantage that the beam must be completely collimated and multiplexed by a method such as using a microlens.

As another beam combining method, there is a method using a prism (for example, see Patent Documents 2 and 3).
However, when multiplexing is performed using a prism as described in Patent Documents 2 and 3, a prism and a lens are required, precise adjustment of the multiplexing position is required, and after multiplexing, The problem is that the beam traveling direction is different from the two incident beams. In addition, since optical coupling using a waveguide used in the field of optical communication is not intended for power transmission, it is not suitable for applications with high power density in terms of reliability and efficiency.

  On the other hand, when light with an arbitrary polarization direction is incident on the birefringent material, the birefringent element is used in the optical communication field because the beam component traveling straight and the propagation direction of the beam energy are separated from the walk-off component deviating from the rectilinear direction depending on the polarization direction. It is often used as a beam splitter (optical demultiplexer) for splitting a beam by using such a method. If the polarizations of the incident beams are perpendicular to each other, beam multiplexing in which the propagation direction in such a birefringent element is reversed can be used (for example, see Patent Documents 4 and 5).

  The light incident on the birefringent element required in this case is an adjacent parallel beam. However, when two adjacent LDs are used side by side with a light source, their polarization directions are equal, so that it is necessary to rotate the polarization direction of one LD beam by 90 degrees before entering the birefringent element.

  As a means for converting an incident beam into an arbitrary linear polarization direction, a so-called polarization-maintaining fiber that emits light in a specific linear polarization direction can be used. However, in order to couple the LD light to a polarization preserving fiber having a small core diameter of usually about 10 μm or less, a minute lens and its precise optical adjustment are required. Also, single mode fibers including polarization maintaining fibers are not very suitable for high power transmission applications due to their small core diameter.

  Further, it is necessary to devise a method of converting the light emitted from the polarization-maintaining fiber into a parallel beam having a desired desired beam interval and to adjust the parallel beam (for example, see Patent Documents 6, 7, 8, and 9). This is because the walk-off amount of the birefringent material is proportional to its propagation length, and the element becomes larger as the incident beams move away from each other.

The walk-off amount is a very small amount of 100 μm per 1 mm in length for a material having a large birefringence such as YVO _4. For example, in order to combine beams with a birefringent element having a length of 5 mm, the distance between incident beams is required. Must be close to 500 μm. There is also a limit to the miniaturization of the device in that an LD and a birefringent element must be arranged corresponding to an appropriate fiber length and bending (angle).

  As another method for changing the polarization direction of the beam emitted from the LD, for example, there is a so-called wave plate such as a phase difference plate, that is, a half-wave plate or a quarter-wave plate. However, in a normal usage, in order to make only one beam of the light from two adjacent LDs incident on the wave plate, the light is used up to the end of the wave plate element. It is necessary to adjust the rotation direction of the LD polarization direction and the crystal axis of the birefringent element and the fast axis of the wave plate, and a member for fixing the wave plate, that is, a so-called mount is required. However, as described above, when the end of the wave plate is used, this mount may block the beam optical path, and fine adjustment thereof causes a reduction in workability in a manufacturing process, and improves productivity and costs. There is a problem that it is difficult to reduce the noise.

US Pat. No. 5,212,710 U.S. Pat. No. 5,291,571 US Pat. No. 6,301,030 B1 JP 2002-72141 A JP-A-10-20352 US Pat. No. 6,295,393 B1 JP-A-11-258453 JP 2001-21750 A JP-A-2002-107579

  The present invention has been made in view of the above-described situation, by beam combining light from a light source such as an LD, and realizing a beam combining element that is small, has high luminance, has a small number of parts, and has a simple optical adjustment. In particular, the present invention provides a beam multiplexing element and a beam multiplexing method which are suitable for use as an excitation light source such as a fiber amplifier laser and have a high light source brightness and are advantageous for power transmission. It is an object to provide a method and an excitation light output device.

  A beam combining element and a beam combining method according to the present invention comprise at least a birefringent material portion and a phase difference portion disposed on at least a part of a beam incident end face of the birefringent material portion. First and second beams or beam groups whose propagation directions are substantially parallel and have substantially the same polarization are incident, and at least one beam or beam group of the first or second beam or beam group is The light is incident on the birefringent material portion via the phase difference portion, the polarization direction is changed by the phase difference portion, and at least one of the first or second beam or the beam group is in the birefringent material portion. Is changed, and the first and second beams or the beam groups form the exit position of the birefringent material portion or, for example, the birefringent material portion is constituted by a plurality of birefringent elements. Expediently, a configuration that is emitted substantially the same direction are multiplexed in the outgoing interface or incident surface.

Further, in the beam splitting element and the beam splitting method according to the present invention, the beam multiplexing element having the above-described configuration uses the beam incident direction and the beam emitting direction in opposite directions.
Further, the pumping light output device according to the present invention has a configuration in which two beams or two groups of beams are multiplexed using the above-described beam multiplexing element, and this is used as pumping light emission light.

  As described above, according to the beam multiplexing device and the beam multiplexing method of the present invention, the same polarization is achieved by arranging the phase difference portion fixedly arranged on at least a part of the beam incident end face of the birefringent material portion. Changing the polarization direction of one beam (group) of the incident beam or beam group (hereinafter referred to as beam (group)) in one direction, and changing the propagation direction of one beam (group) in the birefringent material portion Accordingly, in the case where the birefringent element is composed of a plurality of birefringent elements, or where the birefringent material section is composed of a plurality of birefringent elements, the beam (group) can be combined at the entrance or exit interface.

  Therefore, since the beam multiplexing element can be configured without using a separate fixing member for adjusting the arrangement of the phase difference unit as described above, the beam can be more efficiently emitted without causing beam shading or the like. The beam can be multiplexed, and the size of the beam multiplexing element can be reduced and the characteristics can be improved.

  According to the present invention, by using such a beam multiplexing device, it is possible to provide an excitation light output device that is smaller and has higher luminance than before.

  Further, according to the beam separation element and the beam separation method according to the present invention, similarly, by integrating the retardation portion and the birefringent material portion, the number of parts can be reduced, and the cost can be reduced by eliminating the need for optical adjustment. It is possible to reduce the size and size of the device.

  As described above, according to the beam multiplexing device and the beam multiplexing method of the present invention, two or two groups of substantially parallel beams having the same polarization can be easily multiplexed by one device. Furthermore, it is possible to omit the adjustment mechanism and adjustment work of the optical component, thereby improving the productivity and reducing the cost as well as the number of components.

Further, according to the beam multiplexing device of the present invention, since the allowable range for the incident angle can be expanded as compared with the related art, it is possible to multiplex with a relatively high multiplexing efficiency even if the beam is not a perfect collimated beam. it can. Also, precise optical adjustment for multiplexing can be eliminated.
Further, since the retardation portion and the birefringent material portion are integrated, reliability can be enhanced in terms of strength and ease of handling.

  Therefore, by using the present invention in an excitation light output device that outputs light from a light source such as an LD, a compact and high-luminance light source can be configured. Also, the number of parts can be reduced, and the size of the device can be reduced.

Further, in the present invention, when a half-wave plate is used as the phase difference portion, the cost can be reduced, the manufacturing process can be simplified, and the allowable range of wavelength and temperature can be expanded. A low-order wave plate with a reduced thickness can be used.
This makes it possible to reduce the cost of a device incorporating the beam multiplexing element, and to provide a light output device such as a small and high-brightness excitation light output device.

Further, by bonding the birefringent material portion and the retardation portion with an adhesive, simplification of manufacturing and reduction in cost can be achieved.
Still further, in the present invention, by configuring the birefringent material portion and the retardation portion with the same material, it is possible to suppress the reflected light at the interface between the respective portions and increase the beam use efficiency.
Further, by arranging the auxiliary retardation portion in juxtaposition with the retardation portion, it is possible to protect the incident end face of the birefringent material section, and to reduce variations in processing processes such as surface polishing and thickness adjustment of the incident end face. Thus, the yield can be improved, the handling can be simplified, and the productivity can be improved.

In addition, by forming the retardation portion and the auxiliary retardation portion from the same material, scattering at the interface between them can be suppressed, and the beam use efficiency can be improved.
Further, by making the physical lengths of the phase difference part and the auxiliary phase difference part in the beam propagation direction substantially the same, the optical path length in the beam combining element is made substantially equal, and when an incident beam having a divergence angle is used. The spread of the divergence angle can be suppressed.

  Further, by forming the auxiliary retardation portion from a material having optical isotropy or a transmission plate, optical adjustment such as crystal optical axis alignment at the time of producing the auxiliary retardation portion is not required, thereby simplifying manufacturing. In addition, cost can be reduced.

Further, in the present invention, by providing an optical film having an anti-reflection function on the beam incident end face or the output end face, it is possible to suppress the reflection of the beam and improve the utilization efficiency.
When a laser diode is used as the light source, it is not necessary to adjust the polarization direction of the incident light, so that the optical system can be simplified and the size can be reduced.

  Furthermore, by forming a lens on the entrance end face or the exit end face, or both, it is possible to further reduce the size and to simplify the handling when the lens is incorporated into various devices.

  Further, according to the beam separation element and the beam separation method of the present invention, an optical signal having an arbitrary linear polarization can be demultiplexed into an optical signal having the same polarization. Utilization can be used to simplify the configuration of the demultiplexer, reduce the size, and reduce the cost.

Further, according to the excitation light output device of the present invention, an efficient laser can be realized by providing a compact and high-luminance light source.
In particular, by applying the present invention as a fiber amplifier laser or an excitation light source for a fiber laser, a fiber amplifier laser or a fiber laser with smaller size and higher luminance can be provided.

  Hereinafter, each example of an embodiment according to the present invention will be described with reference to the drawings. However, the present invention is not limited to the following example, and it goes without saying that various other modifications and changes are possible. Absent.

[First Embodiment]
FIG. 1 shows a schematic configuration when an example of the beam multiplexing device according to the present invention is applied to an excitation light output device. In FIG. 1, reference numeral 1 denotes a birefringent material part, and a phase difference part 2 is fixedly arranged on at least a part of the beam incident end face 1A to constitute a beam multiplexing element 10.
Reference numeral 4 denotes a light source such as an LD. In this example, it is assumed that the light source 4 has, for example, linearly polarized light in substantially the same direction along the in-plane direction of the plane of FIG. 1 and emits two beams Li1 and Li2 propagating in the same direction. In such an LD light source, for example, two stripe-shaped resonators are arranged in parallel, that is, each laser element is juxtaposed and arranged in a plane parallel to the active layer, and the beam emission positions are set at, for example, center position intervals. An LD of about 1 mm can be used.

  In this case, the light spot shape of the emitted beams Li1 and Li2 near the end face of the LD element is usually horizontally long. The beams Li1 and Li2 combine in the beam combining element 10 after passing through the birefringent material section 3 due to the polarization rotation by the phase difference section 2 and the walk-off action of the birefringent material section 3 to form one beam. The polarization direction, the thickness and the fast axis direction of the phase difference portion 2, the crystal axis direction and the length of the birefringent material portion 1, and the like are selected so as to be emitted as the emitted light Lo.

  The outgoing beam Lo is coupled to a fiber 7 and the like by an optical system 5 composed of, for example, a collimator lens and an optical system 6 composed of a coupling lens. With such a configuration, for example, the excitation light output device 50 can be configured. Further, the light emitted from the fiber 7 obtained in this manner can be corrected by a lens or the like according to a desired use, and used for various other uses.

  Here, the magnification of the lens of the optical system is determined by taking into account the ratio of the light emitting point width of the light source 4 such as an LD to the core diameter of the fiber 7, and the coupling efficiency in consideration of the divergence angle of the light source 4 and the numerical aperture NA of the fiber 7. Select to be higher. Further, it is desirable that the lenses of the optical systems 5 and 6 are arranged at telecentric positions.

  The conversion mode of the polarization direction of the incident beam in the phase difference unit 2 will be described with reference to FIGS. By converting the polarization direction of one beam into a direction orthogonal to the polarization direction of the other beam, for example, a commercially available half-wave plate or the like can be used as the phase difference unit 2, thereby reducing cost. And the manufacturing process can be simplified.

  FIG. 2 shows a configuration diagram of the beam combining element 10 in FIG. 1 in the case where a half-wave plate is used as the phase difference unit 2, and shows the first and second beams Li1 and Li2 emitted from the light source. The first beam Li1 is incident on the birefringent material section 1 through the phase difference section 2 formed of a half-wave plate. At this time, the polarization directions of the first and second incident beams Li1 and Li2 emitted from a light source such as an LD are the same. In this case, as shown by arrows p11 and p12 in FIG. 2, the vertical direction is along the plane of FIG. Since the polarization direction of the first beam is rotated by about 90 degrees by the action of the phase difference portion 2 composed of a half-wave plate, the first beam is orthogonal to the plane of FIG. It travels with polarized light in the direction.

Here, assuming that the birefringent material portion 1 is a uniaxial anisotropic crystal and its optical axis direction is an oblique direction along the paper surface of FIG. 2 as shown by an arrow a, the polarization direction orthogonal to the paper surface of FIG. The first beam having the following goes straight through the birefringent material section 1 without being subjected to the walk-off action.
On the other hand, the second beam having the polarization direction in the direction along the plane of FIG. 2 undergoes a walk-off action, and the energy propagation direction changes. In FIG. 2, ρ indicates a walk-off angle. The optical axis direction a of the birefringent material portion 1 is, for example, about 45 degrees with respect to the incident direction of the second beam, and the first and second beams have a beam length that exactly intersects at the exit end face of the birefringent material portion 1. If the length of the multiplexing element 10 is selected, the first and second beams emitted from the birefringent material section 1 are emitted from the same emission point in the same propagation direction, that is, become a multiplexed beam Lo. . In FIG. 2, arrows p13 and p23 indicate the respective polarization components included in the combined beam.

  FIG. 3 shows a planar configuration of the phase difference section 2 as viewed from the incident end faces of the first and second beams. A broken line f schematically shows the beam incident end face of the birefringent material portion. Here, it is assumed that the polarization directions of the first and second incident beams Li1 and Li2 are the left and right directions along the plane of FIG. 3 as indicated by arrows p11 and p12, and the phase advance indicated by the arrow e1 of the phase difference portion 2 is indicated. If the angle θ1 between the axis and the polarization direction (arrow p11) before the first beam is incident is set to 45 degrees, the polarization direction of the beam emitted from the phase difference unit 2 is indicated by an arrow p12. As shown, the light is converted into a direction rotated by 90 degrees from before the incidence of the phase difference portion 2. The polarization direction of the second beam that does not pass through the phase difference portion 2 is the same as before the incidence, as indicated by the arrow p22.

Specifically, for example, when YVO ₄ is used as the birefringent material portion 1 and its optical axis forms 45 degrees with the polarization direction of the incident beam, the walk-off angle is in the range of 800 nm to 900 nm of the incident beam. When ρ is 5.8 degrees and the wavelength is about 1300 nm, the walk-off angle ρ is 5.7 degrees. As shown in FIG. 2, when the interval d between the incident beams from the light source is 1 mm, the necessary length l of the birefringent material portion 1 of the beam combining element is approximately
l = d / tan (ρ)
= 10 [mm]
It becomes.

  Therefore, the required length of the beam combining element decreases as the walk-off amount increases. Of course, it goes without saying that the shorter the output beam interval of the LD element, the shorter the required beam combining element length. Table 1 below shows the walk-off amount (angle) with respect to the angle between the incident beam and the crystal axis direction in a typical birefringent material. Each numerical value is for an incident beam at a near infrared wavelength (wavelength 800 nm to 900 nm).

Further, without being limited to YVO ₄ , KTiOPO ₄ (KTP), LiNbO ₃ (LN), and SiO ₂ shown in Table 1, various other materials can be used.
For example, RbTiOPO ₄ (RTP), RbTiOAsO ₄ (RTA), KTiOAsO ₄ (KTA), LiTaO ₃ (LT), MgO-doped LiNbO ₃ , MgO-doped LiTaO ₃ , KNbO ₃ (KN), BaTiO ₃ (BTO), Ba _{2 NaNb 5 O 15 (BNN),} SrBaNbO 7 (SBN), KH 2 PO 4 (KDP), KD 2 PO 4 (dKDP), BaB 2 O 4 (BBO), LiB 3 O 5 (LBO), LiB 4 O 7 , CsLiB ₆ O ₁₀ (CLBO), CsB ₃ O ₅ (CBO), TiO ₂ , calcite (Calcite), MgF ₂ , CaF ₂ , α-Al ₂ O ₃ , and single crystals or eutectics thereof can be used. it can.

In particular, as described above, YVO ₄ , LN, LT, Al ₂ O ₃ , KTP, BBO, and the like have a large walk-off amount, so that the length of the birefringent material portion is shortened, and it is easy to reduce the size. Since SiO ₂ is a general material, it is easy to handle and inexpensive. These materials have an advantage that the manufacturing method is easy because the processing method is established.

  The wavelength of the light used as the incident light is in the range from visible light to the near infrared, that is, a wavelength of 400 nm or more and 1000 nm or less. By obtaining the off amount, beam multiplexing can be performed reliably. Table 2 below shows the walk-off amount (angle) with respect to the angle between the incident beam and the crystal axis direction at the visible wavelength (530 nm).

  Further, when the exit polarization direction of the LD is perpendicular to the paper surface, the propagation direction of the beam incident on the phase difference section 2 is changed in the birefringent material section 1 and the two beams are combined at the exit end face. It can also be done. FIG. 4A is a schematic configuration diagram of this example viewed from the top, and FIG. 4B is a schematic configuration diagram of the example viewed from the side. 4A and 4B, parts corresponding to those in FIGS. 1 and 2 are denoted by the same reference numerals, and redundant description is omitted.

  In this case, the first incident beam Li1 passes through the phase difference portion 2, and its polarization direction is converted into a direction along the paper surface of FIG. 4 as indicated by an arrow p12. The direction of polarization of the second incident beam Li2 in the birefringent material section 1 is, as indicated by an arrow p22, a direction perpendicular to the plane of FIG. 4A. As shown in FIG. 4A, the crystal axis of the birefringent material portion 1 is in an oblique direction along the paper surface, and the energy propagation direction of the first beam passing through the phase difference portion 2 is changed by the walk-off action. It can be configured.

Further, in each of the above-described examples, the retardation portion 2 is made of a holding material that can be fixed to the incident end face of the birefringent material portion 1 at a small interval from the birefringent material portion, such as an air gap type polarizer. It may be used, or may be directly bonded with an adhesive having high transmittance and reliability.
In the bonding step, the phase difference portion 2 and the birefringent material portion 1 may be separately processed and then bonded, or the phase difference portion 2 and the birefringent material portion 1 may be bonded first, and then the phase difference portion 2 may be bonded. Can be adjusted by polishing or the like. In the case of the latter process, the strength of the material is ensured. For example, by using a wave plate having a low wavelength plate order, that is, a thin thickness as the retardation portion 2, the allowable range of the wavelength and temperature can be increased. Can be.

  In each of the above-described examples, by forming the material of the phase difference portion 2 from the same material as the material of the birefringent material portion 1, the difference in the refractive index at the interface between the phase difference portion 2 and the birefringent material portion 1 is obtained. , It is possible to suppress the reflectivity of the beam, and to suppress a decrease in beam use efficiency.

Similarly, each of the parts 1 and 2 is configured such that the refractive index of the phase difference part 2 with respect to the beam incident on the phase difference part 2 and the refractive index of the birefringent material part 1 with respect to this beam are the same. Thus, similarly, it is possible to suppress the beam reflectance and suppress the reduction in the beam use efficiency.
In particular, the material of the adhesive that fixes and arranges the retardation portion 2 to the birefringent material portion 1 is also made of a material whose refractive index is the same as the refractive index of each of the portions 1 and 2 with respect to the incident beam. A decrease in efficiency can be suppressed.

Further, by providing appropriate anti-reflection films on the incident end face and the output end face of each of the retardation section 2 and the birefringent material section 1, the reflectivity of the beam is further suppressed, and the beam is more efficiently combined. Thus, output light with high luminance can be obtained.
When the retardation section 2 and the birefringent material section 1 are bonded with an adhesive, it is desirable to set an antireflection film, a so-called matching film, at the interface with the adhesive in consideration of the refractive index of the adhesive.

In addition, in the examples of FIGS. 1 and 2, the case is described where the angle formed between the main axis of the crystal of the birefringent material portion 1 and the incident beam is 45 degrees. However, the angle is not limited to 45 degrees, but may be various. The crystal optical axis can be selected in a direction in which the walk-off amount is maximized according to the refractive index characteristics of the birefringent material.
Further, the propagation direction of the incident beam may not be completely parallel, and even when each beam is slightly obliquely incident, by adjusting the length of the birefringent material portion 1 and the crystal axis angle, the above-described example can be used. Similarly to the above, multiplexing can be performed on the exit end face of the birefringent material portion 1.

By employing such a configuration, the space occupied by the optical path from the light source 4 such as an LD to the fiber 7 can be reduced as compared with the related art.
In addition, since it is not necessary to separately provide a support for holding the phase difference portion 2, that is, a mount, a close LD element can be used as a light source, for example. Therefore, the cooling mechanism such as the electrodes of the LD and the Peltier element can be shared, and a small output light source having twice the output, twice the luminance and the same output of each LD element can be realized.

  Further, in the present invention, since the retardation portion and the birefringent material portion are integrated, handling is easy and strength is secured. In addition, optical adjustment such as the phase axis of the phase difference part and the crystal axis angle of the birefringent material part is performed in the manufacturing process, and the multiplexing position is determined by adjusting the length of the birefringent material part. When the optical head is incorporated into the device, there is no need for the user to make delicate optical adjustments, and workability such as incorporation into an excitation light output device or the like is greatly simplified.

  Further, as described above, according to the present invention, even if an LD light source having the same characteristics is used, twice the luminance and output can be achieved, so that the present invention is particularly suitable for applications in which the efficiency and characteristics greatly change depending on the luminance. ing. For example, the present invention is suitable for a case where a large amount of laser power must be applied at a limited angle to a minute area such as a fiber core of a fiber amplifier laser as a laser excitation light source.

In addition, for applications such as processing, medical use, and printing, by increasing the luminance according to the present invention, a new application to the processing / treatment field that appears at a luminance equal to or higher than a certain threshold becomes possible, or Takt time can be reduced.
Furthermore, also in the communication field, it can be used as an excitation light source for optical amplification in order to compensate for the loss of an optical signal. Thus, the effect of achieving the effect can be obtained.

  In the examples shown in FIGS. 1, 2 and 4, the direction in which the LD elements are arranged is transverse to the traveling direction of the incident beam. However, the present invention is not limited to this. It is also possible to adopt a configuration in which LD elements are arranged in parallel in a direction perpendicular to the direction. In this case, the emitted beams are arranged in a vertical stack in the vicinity of the emission end face, but the beams can be combined using the beam combining element according to the present invention.

  In the case of configuring the LD element in this manner, the center of the stripe can be made closer, so that the length of the birefringent material portion, that is, the length of the beam combining element can be shortened. Further, the polarization direction of the LD in the above-described first embodiment is an example, and the beam multiplexing device according to the present invention is configured for an LD having a polarization direction perpendicular to the plane of FIG. What can be done is as described above.

  Further, in the above-described example, the configuration of the optical systems 5 and 6 is merely an example, and it goes without saying that the type of lens, the arrangement of the optical system, and the like may take various other forms. The beam after exiting the beam combining element may be composed of an infinite lens system that is once converted into a parallel beam. As shown in FIG. 5, a schematic configuration of an example is shown in FIG. It can also be configured by a finite system. 5, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and redundant description will be omitted.

  In the case of using a finite optical system as described above, lens aberration and the like do not become a problem, and particularly when the optical axes of the LD and the fiber are matched in advance, it is effective in reducing the number of parts and the labor for adjustment. It is. Further, the beam emitted from the collimating lens 6 described in FIG. 1 can be used as it is for various devices without coupling to the fiber.

  In such a beam multiplexing device, generally, the allowable width of the phase difference portion such as the wavelength plate with respect to the incident angle is larger than the allowable angle of the PBS (polarizing beam splitter), and the allowable angle of the birefringent material portion. Is relatively large, so that there is an advantage that the light emitted from the LD can be sufficiently multiplexed even if it is not collimated.

  If the divergence angle of the light emitted from the LD prevents the beam multiplexing element from being miniaturized or causes a reduction in its coupling performance, for example, FIGS. As shown in the configuration, the beam having a larger divergence angle, for example, the beam spread in the direction perpendicular to the cavity length direction of the normal LD and perpendicular to the active layer is appropriately suppressed by using a lens 8 such as a cylindrical lens. A configuration in which the light is incident on the beam combining element 10 can be adopted. 6A and 6B, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted.

  As described above, according to the first embodiment of the present invention, the beam multiplexing device is manufactured with a simple configuration by arranging the retardation unit 2 fixedly on the birefringent material unit 1. It does not require delicate optical axis adjustment etc. by the user when installing it, and furthermore, it is possible to suppress a decrease in beam use efficiency, and obtain a compact and high-brightness output light. Beam combining element can be provided.

  In addition, by forming the retardation section 2 by a half-wave plate, it is possible to manufacture by a simple manufacturing method in which only the fast axis and the crystal axis of the birefringent material section 1 are fixedly arranged. Further, it is possible to provide a small-sized, high-brightness output light source with a simple manufacturing process.

[Second embodiment]
Next, a second embodiment according to the present invention will be described.
In the above-described first embodiment, only one of the beams incident on the beam combining element is made to enter the phase difference portion. In the following example, FIG. 7 shows a schematic configuration of one example. Thus, the case where the auxiliary retardation portion 3 is provided on the incident end face 1A of the birefringent material portion 1 in parallel with the retardation portion 2 will be described. 7, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted.

  Also in this case, for example, a light source in which two LD elements are used in parallel is used. In this example, the propagation direction is almost the same, and as shown by arrows p11 and p21, a straight line in the vertical direction along the paper surface of FIG. First and second incident beams Li1 and Li2 to be polarized are incident on the birefringent material section 1 via the phase difference section 2 and the auxiliary phase difference section 3, respectively.

  Here, it is desirable that the auxiliary retardation portion 3 is a transmission plate made of a material having substantially the same thickness as the retardation portion 2 and having a refractive index close to the polarization direction of the incident beam. That is, the phase difference part 2 and the auxiliary phase difference part 3 having substantially the same refractive index are arranged on the incident side of the beam combining element 10 and the thicknesses thereof are made substantially the same, so that the two beams in the element 10 are formed. Can be made substantially equal. For example, when the beam incident on the beam multiplexing element 10 has a divergence angle, the shape and divergence angle of the beam emitted from the beam multiplexing element 10 can be substantially suppressed.

  In addition, the interface between the retardation section 2 and the auxiliary retardation section 3 is bonded with an adhesive or the like having a refractive index substantially the same as the refractive index of each section 2 and 3 so that the same refractive index can be obtained. Since the interface of the material is hardly reflected, the scattered light at the interface between the phase difference portion 2 and the auxiliary phase difference portion 3 between the two beams can be suppressed, and the light returned to the light source can be suppressed.

  Further, in the manufacturing process, a process in which the retardation portion 2 and the auxiliary retardation portion 3 are first fixed to the incident end face 1A of the birefringent material portion 1 with an adhesive or the like, and then the surfaces are polished may be adopted. In addition, since a large polishing area can be ensured, variations such as parallelism due to polishing can be suppressed. Further, an optical mirror surface can be secured up to the end of the phase difference portion 2. Further, by providing the auxiliary retardation section 3, the incident end face 1A of the birefringent material section 1 can be protected.

  As such an auxiliary retardation portion 3, for example, a material having optical isotropy, for example, optical glass such as BK7 and SF11 can be used. FIG. 8 shows a schematic plan configuration viewed from the incident end face side in FIG. When the auxiliary retardation portion 3 is made of a material having optical isotropy as described above, the polarization direction before entering the auxiliary retardation portion 3 (arrow p21) and the polarization direction after exiting (arrow p22) are Not converted.

  On the other hand, the phase difference section 2 is constituted by a half-wave plate, as in the example described in FIG. 2 showing an example of the first embodiment, thereby rotating the polarization direction of the incident beam by 90 degrees. Can be done. 8, parts corresponding to those in FIG. 3 are denoted by the same reference numerals, and redundant description will be omitted.

  Further, as shown in FIG. 9, as an example of a schematic plan configuration, the auxiliary retardation portion 3 is made of the same birefringent material as the retardation portion 2, and its crystal axis is aligned with the polarization direction of the incident beam. By configuring so as to be substantially in the same direction, that is, for example, the fast axis of the auxiliary phase difference portion 3 is in the same direction as the polarization direction (arrow p21) of the beam before incidence as shown by the arrow e3. With this configuration, it can function as a transmission plate that preserves the polarization direction. 9, parts corresponding to those in FIG. 8 are denoted by the same reference numerals, and redundant description will be omitted. The arrow e4 indicates the direction of the slow axis of the auxiliary phase difference unit 3.

In this case, by using the same material for the retardation section 2 and the auxiliary retardation section 3, reflection at the interface between the retardation section 2 and the birefringent material section 1 can be suppressed, and a decrease in the utilization efficiency can be suppressed.
Further, since the difference in the coefficient of thermal expansion can be reduced, handling regarding the processing process and the method of use is facilitated.
Note that the polarization direction of the LD in the above-described second embodiment is merely an example, and for example, even when the polarization of the light source is circularly polarized, the beam multiplexing device according to the present invention can be configured. Not even. In the case of such a polarization direction, the phase difference portion 2 and the auxiliary phase difference portion 3 for converting circularly polarized light into linearly polarized light orthogonal to each other are respectively provided to the passing portions of the first and second beams Li1 and Li2 in FIG. May be provided.

[Third Embodiment]
Next, an embodiment in which a lens is integrally provided on the entrance end face or the exit end face of the beam combining element according to the present invention will be described. In this example, the auxiliary retardation section 3 described in the second embodiment is juxtaposed to the retardation section 2 and has substantially the same thickness, that is, the retardation section 2 and the auxiliary retardation section. 3 shows an example applied to a case where the incident end face is a flat same plane.
That is, as shown in FIGS. 10A and 10B, an example of a schematic plan configuration and a side configuration, respectively, a lens 9 is provided on the incident end faces of the phase difference unit 2 and the auxiliary phase difference unit 3 so that a beam integrated with a lens is formed. A multiplexing element is formed.

  In this case, by using a cylindrical lens as the lens 9, the divergence angle of light from an LD or the like can be reduced, so that a decrease in beam use efficiency is suppressed and the size of the beam combining element is reduced. And the collimated beam can be easily collimated. Also in this case, the number of components can be reduced, and the optical adjustment work can be reduced, so that the device incorporating the elements of the beam multiplexing device can be further downsized and the device configuration can be simplified.

  Further, as shown in FIGS. 11A and 11B, a schematic plan configuration and a side configuration of this example, a lens 11 can be similarly provided on the emission end face side of the birefringent material portion 1. For example, after multiplexing the beams in the beam multiplexing element 10, the beams can be emitted as substantially parallel beams by a lens 11 such as a collimator lens attached to the emission end face. In this case, the focal length of the collimator lens is selected so that the beam emitted from the light source 4 is collimated just after being emitted from the beam combining element 10.

  As a method for attaching such a lens 9 or 11, it is desirable that the lens 9 or 11 is adhered to the birefringent material portion 1 of the beam combining element 10 with an optically substantially transparent adhesive or the like. Further, it is desirable to apply an appropriate antireflection film to the birefringent material portion 1 and the adhesive, between the adhesive and the lens 9 or 11, and further on the surface of the lens 9 or 11. By providing such an anti-reflection film, it is possible to prevent return light to a light source such as an LD and to suppress a laser power loss in a beam combining element having a lens attached thereto.

  Note that, as shown in FIG. 11, when the curved surface of the lens 11 faces the collimated light side, the aberration of the lens can be reduced. When the lens has an aspherical shape, the aberration can be further reduced. Therefore, beams can be combined more efficiently.

  Further, lenses 9 and 11 can be provided on both the incident end face and the exit end face. In this case, the beam utilization efficiency is further improved, and the manufacturing method by downsizing the device incorporating the beam combining element and simplifying the optical adjustment is also possible. Simplification, and therefore, an improvement in productivity.

Further, by configuring the beam multiplexing device in which the optical system is integrated as described above, it is possible to provide an ultra-compact high-brightness excitation light generator.
Furthermore, when assembling and configuring a beam combining element with a lens having an appropriate outer shape accuracy by ensuring the outer shape accuracy of each component, the work of optical adjustment is further omitted and mechanical stability is ensured. You can do it. As an optical adjustment method of each component, for example, by aligning the optical axis with a parallel beam such as a He-Ne laser, the beam multiplexing element can be bonded and assembled with a predetermined outer shape accuracy by a relatively simple operation. it can.

The combination of the beam multiplexing element and the lens in the above-described embodiment and the operation thereof are not limited to the above-described example, and various modifications and changes such as the type of lens and the mounting method can be made. For example, by deforming the surface of the birefringent material portion 1, it is possible to have a lens function. When the aberration is small, the lens shape may be, for example, a spherical shape. Further, a lens attached to the exit end face of the birefringent material portion 1 may be a condenser lens and directly coupled to the fiber.
As the material used for the lens, each material shown as the material of the above-described birefringent material portion can be used. Further, optical glass such as BK7 and SF11 can be easily used.

[Fourth Embodiment]
Next, each example of an embodiment in which the phase difference portion and the auxiliary phase difference portion are configured by combining various phase difference plates, so-called wavelength plates, will be described.
In each of the above-described embodiments, an example in which a 波長 wavelength plate is used as a phase difference unit has been described. In this example, a case in which a 波長 wavelength plate is combined is shown.

  FIG. 12 is a diagram illustrating a schematic configuration of the phase difference unit 2 and the auxiliary phase difference unit 3 when viewed from the top when the phase difference unit 2 and the auxiliary phase difference unit 3 are each configured by two quarter-wave plates. The phase difference section 2 is constituted by quarter-wave plates 21 and 22, and the auxiliary phase difference section 3 is constituted by quarter-wave plates 31 and 32. Of the incident beam, the beam passing through the phase difference portion 2 is polarized by the arrow p12 after passing through the phase difference portion 2 assuming that the polarization direction is the horizontal direction along the paper surface of FIG. As shown in FIG. 12, the auxiliary phase difference unit 3 has a configuration in which the polarization direction of the incident beam is changed by 90 degrees in a direction orthogonal to the plane of FIG. The configuration is not performed.

  More specifically, for example, as shown in FIG. 13, which shows a schematic plan configuration viewed from the incident direction of the beam, the direction of the fast axis of the 波長 wavelength plate 21 of the phase difference portion on the incident end face side (ie, the light source side) is As shown by the arrow e1, the polarization direction of the incident beam shown by the arrow p11 and the angle θ4 are set to 45 degrees, and the direction of the fast axis of the quarter wave plate 31 of the auxiliary phase difference portion is shown by the arrow e5. As shown, the arrangement is selected so that the angle θ5 with respect to the polarization direction of the incident beam indicated by the arrow p21 is 45 degrees opposite to the direction of θ4, and each fast axis forms 90 degrees. In this case, the incident beams passing through the quarter-wave plates 21 and 31 are converted into rightward and leftward circularly polarized lights, respectively, as indicated by arrows p11a and p21a, respectively.

  The direction of the fast axes of the quarter wave plates 22 and 32 of the phase difference part and the auxiliary phase difference part on the side of the birefringent material part is schematically shown in FIG. 14 as viewed from the incident direction of the beam. As shown by the arrow e1, the angles θ6 and θ7 with respect to the polarization direction of the incident beam before entering the phase difference part 2 and the auxiliary phase difference part 3 are 45 degrees, similarly to the quarter wavelength plate 21. To convert each of the beams incident as circularly polarized light as indicated by arrows p11a and p21a into linearly polarized beams having polarization directions orthogonal to each other as indicated by arrows p12 and p22, respectively. be able to. In this example, the configuration is such that the polarization direction of the incident beam that has passed through the phase difference unit 2 is changed by 90 degrees.

By using such a combination of retardation plates, specifically, the same operation as that of the above-described second embodiment can be achieved only by changing the attaching direction of one of the same quarter-wave plates. The phase difference part and the auxiliary phase difference part can be configured.
Here, even if the quarter-wave plates 21 and 22, and 31 and 32 are respectively arranged in the reverse order to the propagation direction of the incident beam, the same polarization direction conversion action can be obtained. Instead of the quarter-wave plates 22 and 32, one so-called horizontally long quarter-wave plate may be provided, and the retardation section 2 is configured using one half-wave plate. Needless to say, other various modifications and changes are possible.

Furthermore, as a half-wave plate, two wave plates having different thicknesses are attached to each other so that the fast axis and the slow axis of the wave plate are orthogonal to each other, and the refractive index between the two intrinsic polarizations is set. The difference Δn and the thickness difference Δt are
Δn · Δt = (k + ／) λ
(K is an integer of 0 or more)
Thus, a half-wave plate can be formed by forming each wave plate, that is, a wave plate obtained by bonding a retardation plate so that the polarization direction is converted by 90 degrees can be used.

  That is, without being limited to each of the above-described examples, the 90-degree conversion is performed only in one of the phase difference portion and the auxiliary phase difference portion before and after the incidence, and the polarization direction is not changed in the other. The same effects as those of the first and second embodiments can be obtained.

Even when the polarization direction is changed to a direction other than 90 degrees, only one of the two incident beams undergoes the walk-off effect and propagates by taking into account the arrangement of the birefringent material with the crystal axis. By arranging the directions to be changed, it is possible to perform beam multiplexing according to the present invention.
However, as described above, in a case where the polarization direction is changed by 90 degrees, the beam alignment can be relatively easily performed only by aligning the polarization direction of the incident beam with the crystal axis of the birefringent material portion. There is an advantage that a wave element can be configured.

[Fifth Embodiment]
In each of the above-described embodiments, an example has been described in which the beam combining element is configured using a rectangular parallelepiped birefringent element as the birefringent material portion. An example of a modified Wollaston type configuration in which a birefringent material portion is formed by bonding two birefringent elements by applying a Wollaston prism in which two are combined is shown.

  In this case, the birefringent material portion is composed of a birefringent element 41 on the beam entrance side and a birefringent element 42 on the exit side, as shown in FIG. A partially inclined surface is provided on the incident end surface side of the birefringent element 41 on the incident side, the first beam Li1 is incident on the incident end surface 41A1 orthogonal to the propagation direction, and the second beam Li2 is incident at a constant incident angle. And the beams Li1 and Li2 are incident at different angles. The phase difference portion 2 can be formed by, for example, attaching a phase delay film to the incident end face 41A2 of the second beam Li2.

  On the other hand, the outgoing end face 41B of the birefringent element 41 is also formed as an oblique inclined face, and the incoming end face 42A of the other birefringent element 42 is fixedly arranged to face the inclined face. The exit end face 42B of the birefringent element 42 is configured as a plane orthogonal to the propagation direction of the exit beam.

The manner of converting the polarization directions of the incident beams Li1 and Li2 in such a configuration will be described.
The polarization direction of each incident beam is, for example, as shown by arrows p11 and p12, which is perpendicular to the plane of FIG. 15, and the crystal axis directions of the birefringent elements 41 and 42 are arrows a1, b1, and c1, respectively. Further, as shown by a2, b2 and c2, for example, it is assumed that one crystal axis direction a1 and a2 is the same direction and both directions are perpendicular to the paper surface of FIG.

Here, the first incident beam Li1 is perpendicularly incident on the incident end face 41A1 of the birefringent element 41. At this time, since the polarization component is along the crystal axis, the polarization direction goes straight through the birefringent element 41 without being changed as indicated by the arrow p12.
The other beam Li2 is obliquely incident on the phase difference portion 2, and by the action of the phase difference portion 2, the polarization direction is converted into an oblique direction along the paper surface of FIG. Then, the two beams are emitted from the birefringent element 41 so as to converge at a predetermined position by the walk-off action, and enter the birefringent element 42.

  At this time, as described above, the birefringent elements 41 and 42 are both configured to have the same crystal axis in a direction perpendicular to the plane of FIG. With such a configuration, since the refractive indexes of the beams having polarizations in the direction perpendicular to the paper surface of FIG. 15 are equal inside the birefringent elements 41 and 42, the first beam is , Again propagating straight in the same direction. Arrows p122 and p222 indicate the polarization direction of each beam in the birefringent element 42, respectively.

  On the other hand, the angle of the interface between the birefringent elements 41 and 42 is such that the second beam exiting the birefringent element 41 with the polarization direction along the plane of the paper of FIG. It is determined that the wave propagates.

  For example, as shown in FIG. 15, the beam multiplexing position surrounded by a broken line g in FIG. 15 is enlarged and shown in FIG. 16, the angles, intervals, and further birefringence of the end faces 41B and 42A of the first and second birefringent elements 41 and 42 are shown. By appropriately selecting the refractive indices and the like of the elements 41 and 42, the beams Li1 'and Li2' are emitted from the emission end face 41B of the first birefringent element 41 at different angles, respectively. Are multiplexed at the incident end surface 42A of the second birefringent element and are emitted from the second birefringent element as an outgoing beam Lo.

  Alternatively, as shown in an enlarged manner in FIG. 17, the beam multiplexing position is such that the beams are multiplexed at the exit end face 41B of the first birefringent element 41 and one beam is output from the first birefringent element 41. It can also be emitted as Li3 and made incident on the second birefringent element 42, from which it can be emitted as an emitted beam Lo. In this case, an isotropic medium such as optical glass can be used instead of the birefringent element. 16 and 17, parts corresponding to those in FIG. 15 are denoted by the same reference numerals, and redundant description will be omitted.

When the birefringent material portion having such a modified Wollaston type configuration is formed, as described above, in addition to the refractive index and the crystal axis angle of each birefringent element forming the birefringent material portion, FIG. As shown in the figure, for example, the distance d1 from the upper surface of the birefringent element 41 to the point of incidence of the first beam, the distance d2 before the first and second beams Li1 and Li2 are incident, the distance d1 from the upper surface of the birefringent element 41, The distance d3 to the upper end of the phase difference portion 2, the beam incident on the phase difference portion, the incident angle θ11 of the second beam to the phase difference portion 2 in this case, and the shape of each birefringent element are, for example, Lengths l1 and l2 of the birefringent elements 41 and 42 on the upper surface along the propagation direction of one incident beam Also, the angles θ12 and θ13 formed by the upper surface and the inclined surface facing each birefringent element (that is, the exit end face 41B of the birefringent element 41 and the incident end face 42A of the birefringent element 42), and the angles of the birefringent elements 41 and 42 By appropriately selecting the interval l3 and the like, the first and second beams having the polarization directions in substantially the same direction are multiplexed at the same position and the same as in the first to third embodiments. The light can be propagated in the direction and emitted.

[Sixth Embodiment]
In each of the above-described examples, an example in which beams from two light sources such as LDs are combined has been described. In the present embodiment, for example, a beam from a light source that emits a large number of beams such as an array laser is used. An example in which two of them are combined will be described.
In FIG. 19, reference numeral 1 denotes a birefringent element made of KTP or the like. Are fixedly arranged with substantially the same thickness.
Then, n (n is an integer of 1 or more) first group and second group beams Li11 to Li1n and Li21 to Li2n of n (n is an integer of 1 or more) are incident on the phase difference portion 2 and the auxiliary phase difference portion 3, respectively.

  Also in this case, the polarization direction of each beam, the length of the birefringent material portion 1 in the beam propagation direction, and the crystal axis direction are selected as in the example of FIG. 7 and the like described in the second embodiment. Thereby, the beams of each group are multiplexed at the exit end face of the birefringent material portion 1, that is, 2n beam groups can be multiplexed into n outgoing beams Lo1 to Lon.

  With this configuration, the number of beams of the array LD and the like can be halved, the luminance can be doubled, and the array beams can be easily focused.

Further, as shown in FIG. 20, an example of the structure is prepared by preparing two beam multiplexing elements described in FIG. 19 and combining the output beam positions close to each other, for example, 2 (n + m) pieces (m is (An integer of 1 or more) incident beams Li11 to Li1n, Li21 to Li2n, Li31 to Li3m, and Li41 to Li4m can be combined into (n + m) outgoing beams Lo1 to Lon + m.
In the case of the configuration shown in FIG. 20 as compared with the example of FIG. 19, the walk-off amount can be reduced. For example, when m = n, in the example shown in FIG. 20, since the necessary walk-off amount is reduced by half, the length of the birefringent material portion 1 is reduced by half compared to the configuration example of FIG. can do. Therefore, the length of the birefringent material portion 1 can be reduced, which is advantageous for miniaturization.

[Seventh Embodiment]
By using the beam multiplexing device according to the present invention, if the beams are close to each other, the lateral shift can be corrected and the beams can be superimposed on the same beam.
FIG. 21 illustrates the operation of the beam multiplexing element 10 for correcting a lateral beam shift of the optical element 60 having a large chromatic aberration. 21, parts corresponding to those in FIG. 7 are denoted by the same reference numerals, and redundant description will be omitted.

  When the incident beam Li has a different wavelength component, particularly when the wavelength difference is large, the beam emitted from the optical element 60 may cause a lateral shift of the beam due to the influence of the chromatic aberration due to the wavelength. In the case where the lateral shift amount is large and the output beams are separated as indicated by Li1 and Li2, the beam combining element 10 in which the length of the birefringent material portion is adjusted in accordance with the lateral shift amount, as shown in FIG. It can be arranged at the subsequent stage of the optical element 60 and multiplexed into one beam Lo again. For example, when the lateral shift amount is large because the wavelength difference is large, it is very effective.

  The configuration is such that the polarization direction of one beam Li1 indicated by arrow p11 is converted by 90 degrees by the phase difference portion 2 such as a wave plate on the incident side of the beam multiplexing device 10, so that the beam after exiting the beam multiplexing device can be obtained. Is a beam having polarization directions p12 and p13 orthogonal to each other. However, for example, a phase difference portion having a configuration that acts as a half-wave plate for a beam of a specific wavelength and does not exhibit a wavelength plate effect for beams of other wavelengths is designed, and this phase difference portion is combined with a beam. By arranging the two beams after the element, the two beams can be returned to the same polarization direction. If a similar phase difference portion is attached instead of the phase difference portions 2 and 3 at the incident end of the beam combining element, the lateral displacement can be corrected even for overlapping beams whose beam lateral displacement is smaller than the beam diameter. Such a wave plate can be realized by a high-order wave plate, a wave plate formed by bonding different materials, or the like.

[Eighth Embodiment]
Next, an operation mode of the beam multiplexing element that performs walk-off correction by wavelength conversion will be described with reference to FIG. 22, parts corresponding to those in FIG. 21 are denoted by the same reference numerals, and redundant description will be omitted. For simplicity, it is assumed that the wavelength conversion is the generation of the second harmonic of type 1 (that is, the incident polarization is only ordinary light). As shown by an arrow pi, when the incident beam Li whose direction of polarization is perpendicular to the plane of the paper of FIG. 22 is incident on the wavelength conversion element 70, the fundamental light goes straight and is emitted as the first beam Li1, and the wavelength is changed. The converted light that is converted into half is inclined at a certain angle in the propagation direction, and then emitted in parallel with the first beam Li1, which is the emission beam of the basic light, at a certain interval. This is the second beam Li2. For example, assuming that the wavelength of the incident light is 1064 nm, the wavelength of the first beam Li1 is equal to the wavelength of the incident beam Li, and the wavelength of the second beam Li2, which is the converted light, is half of the fundamental light, that is, light of, for example, 532 nm. .

  The polarization direction of the second beam Li2 is an extraordinary ray, and the polarization direction is a beam having a polarization direction (arrow p21) orthogonal to the polarization direction indicated by the arrow p11 of the incident basic light, and the second beam Li2 is a walk beam. Due to the OFF action, the shape of the output beam becomes a horizontally long beam shape. In the high-efficiency wavelength conversion element 70, the fundamental light is attenuated as much as it is converted, and the conversion efficiency drops sharply with respect to the traveling direction of the beam. Therefore, the energy component of the output beam is shifted in a direction away from the residual fundamental light. concentrate. In such a case, by arranging the beam multiplexing element 10 as shown in FIG. 22 with respect to the fundamental light and the converted light after the wavelength conversion, that is, the beams Li1 and Li2, one beam is utilized by using the walk-off effect. Can be combined.

  In this case, the polarization directions of the fundamental light and the converted light incident on the beam combining element 10 are different. The polarization direction of the fundamental light can be converted to the same direction as the polarization direction of the converted light by providing a wavelength plate on the end face on which the fundamental light is incident. In this case, as shown in FIG. 22, if both the polarization directions of the beams indicated by arrows p21 and p22 and the crystal axis direction of the birefringent material part 1 are along the paper plane of FIG. 22, both beams have a walk-off effect. Will receive it. However, since the wavelengths of the two beams are different, each material and the wavelength are set so that the converted light having a wavelength of, for example, approximately を has a larger walk-off amount with respect to the fundamental light corresponding to the interval between Li1 and Li2. By the selection, the basic light and the converted light can be multiplexed at the emission end face of the birefringent material portion 1 and emitted as one beam propagating in the same direction.

  Further, when the sum frequency of the type 1, that is, the third harmonic is generated by using the emitted light after the beam multiplexing, the conversion can be performed efficiently because the beams are overlapped. Needless to say, it is preferable to arrange an appropriate lens before and after each wavelength conversion element. Further, the length of the wavelength conversion element 70 can be set to be large enough to separate the emitted beam. In the case where the fundamental light and the converted light are made to enter the birefringent material part 1 with orthogonally polarized light without providing a phase difference part, when the sum frequency is generated using the emitted light, type 2 (normally incident light is used) Rays and extraordinary rays).

  On the other hand, by using the beam multiplexing element according to the present invention, in this case, a phase difference portion that acts as a half-wave plate only for the basic light after emission is disposed, and wavelength conversion (sum frequency generation) at the subsequent stage is performed. , The beam polarization directions can be equalized, and type 1 sum frequency mixing can be performed.

  As described above, by using the beam multiplexing element according to the present invention, it is possible to correct the lateral shift of the beam due to the wavelength and the polarization, multiplex the beam into one beam and improve the beam profile, and to simplify the handling of the beam. Therefore, it is possible to simplify the device configuration of the wavelength conversion device, thereby achieving downsizing and high efficiency.

[Ninth embodiment]
Next, an embodiment of a beam separating element according to the present invention will be described with reference to FIG.
The beam separation element 20 of the present invention has a configuration in which the birefringent material portion 1 and the phase difference portion 2 are fixedly arranged on a part of the emission end face. Arrow a indicates the crystal optical axis of the birefringent material portion 1. In FIG. 23, reference numeral 12 denotes, for example, a collimator lens. When incident light Li having a polarization component indicated by arrows p31 and p41 is incident on the birefringent material portion 1, the beam is separated into an ordinary ray and an extraordinary ray by a birefringent action. Is done. At this time, the polarization direction of each beam is converted into two directions, that is, a direction p32 perpendicular to the paper surface and a vertical direction p42 perpendicular to the paper surface, for example, a vertical direction p42 along the paper surface.
By passing one beam through the phase difference unit 2 and changing the polarization direction, it is possible to separate the two beams into two beams Lo1 and Lo2 having the same polarization direction p33 and p43. Needless to say, a lens such as a collimator lens may be arranged depending on the characteristics of the incident light, and if necessary.

By using such a separating element and combining with the above-mentioned multiplexing element, it can be used for various demultiplexing / multiplexing apparatuses, wavelength routers, polarization-independent optical isolators and the like used in the optical communication field. .
For example, by using the above-described multiplexing element, in the optical communication field, two beams of signal light having the same polarization can be multiplexed into one beam of signal light having polarization directions orthogonal to each other. The wavelength and other characteristics of the incident beam may be different. When the wavelengths are different, the phase difference portion and the birefringent material portion may be designed according to the wavelength of each beam.

  Further, by using the beam separation element shown in FIG. 23, for example, the signal light can be split by polarization. Also in this case, as shown in FIG. 23, the beam propagation direction and the input / output end face in each of the above-described embodiments may be reversed. By arranging such demultiplexing / multiplexing elements in order and by arranging an optical element having a desired purpose between the demultiplexing element and the multiplexing element, the characteristics of the signal light can be changed to only one side of the beam or to both sides. Both the beam and the characteristics can be converted.

  The optical element referred to here is, for example, a wavelength filter, an isolator, an optical modulator, or the like. For example, an optical switch can be configured using an optical element such as an optical modulator using an electro-optic effect or an acousto-optic effect, which actively performs optical conversion by signal input.

Furthermore, even if the optical element has a polarization-dependent characteristic such as an isolator, the use of the demultiplexing element can separate the light into two beams of the same polarization, and the optical element depends on the polarization direction. Is appropriately arranged, and is combined again into one beam by the beam combining element in the subsequent stage, so that it can function as a polarization independent optical element.
Further, when a plurality of beam groups are incident instead of one beam, the beam groups can be separated into twice as many beam groups, and the configuration of the apparatus can be simplified and downsized by using the apparatus for various demultiplexers. Is also possible.

  In any of the examples described above, by using the beam multiplexing element / demultiplexing element according to the present invention, the phase difference portion and the birefringent material portion are integrated, so that alignment is easy and miniaturization is possible. There is an advantage that the optical device can be manufactured at low cost.

  As described above, according to the present invention, since the phase difference portion and the birefringent material portion are integrated in the beam multiplexing device or the beam splitting device, reduction of the adjustment mechanism of the optical component and the adjustment work can be omitted. Thus, strength and ease of handling can be improved, productivity can be improved, cost can be reduced by reducing the number of parts, and reliability can be improved.

  Further, according to the beam multiplexing device of the present invention, since the allowable range for the incident angle can be expanded as compared with the related art, it is possible to multiplex with a relatively high multiplexing efficiency even if the beam is not a perfect collimated beam. it can. Also, precise optical adjustment for multiplexing can be eliminated.

According to such an excitation light output device using a beam combining element according to the present invention, an efficient laser can be realized by providing a small and high-luminance light source.
In particular, by applying the present invention as a fiber amplifier laser or an excitation light source for a fiber laser, a fiber amplifier laser or a fiber laser with smaller size and higher luminance can be provided. In addition, when used as an excitation light source for optical amplification in optical communication, it is possible to obtain an effect of increasing the amplification interval in addition to reducing the size.

It can also be used as a beam multiplexing device in optical communications, etc., and in an optical communication device using various beam multiplexing elements, the reliability of the beam multiplexing device in terms of miniaturization, strength, and ease of handling is reduced. Can be improved.
In addition, by using the beam multiplexing device and the beam multiplexing method according to the present invention for laser processing, medical use, a printing device, and the like, the size and cost of the device can be similarly reduced.

Further, since lights of different wavelengths can be multiplexed, the lateral displacement of the beam can be corrected in an optical element having a large chromatic aberration.
Further, by applying the beam multiplexing device and the beam multiplexing method according to the present invention to a multi-stage wavelength conversion device, that is, a third harmonic generation device and a fourth harmonic generation device using the second harmonic light, the converted light can be obtained. Can be easily multiplexed on the same optical axis as the fundamental wave, eliminating the need for adjusting the arrangement of the phase difference plate and each optical system, and reducing the wavelength conversion for sum frequency generation. High efficiency, improved beam profile, and downsizing of the apparatus can be achieved.

  Further, according to the beam separation element and the beam separation method according to the present invention, an optical signal having an arbitrary polarization can be split into an optical signal having the same polarization, so that it can be used as any beam splitter in optical communication and the like. However, simplification, downsizing, and cost reduction of the demultiplexer configuration can be achieved.

  As described above, each example of the embodiment according to the present invention has been described. However, it is needless to say that the present invention is not limited to each of the above embodiments, and that various other modifications and changes are possible.

It is a block diagram of an example of a beam multiplexing element and an excitation light output device. It is a block diagram of an example of a beam multiplexing element. FIG. 4 is an explanatory diagram of a polarization mode of an example of a phase difference section. FIG. 2A is a configuration diagram illustrating a planar configuration of an example of a beam combining element. B is a configuration diagram illustrating a side configuration of an example of the beam combining element. It is a block diagram of an example of a beam multiplexing element and an excitation light output device. FIG. 2A is a configuration diagram illustrating a planar configuration of an example of a beam combining element. B is a configuration diagram illustrating a side configuration of an example of the beam combining element. It is a schematic block diagram of an example of a beam multiplexing element. FIG. 4 is an explanatory diagram of a polarization mode of an example of a phase difference section. FIG. 4 is an explanatory diagram of a polarization mode of an example of a phase difference section. FIG. 2A is a configuration diagram illustrating a planar configuration of an example of a beam combining element and an excitation light output device. B is a configuration diagram illustrating a side configuration of an example of the beam combining element. FIG. 2A is a configuration diagram illustrating a planar configuration of an example of a beam combining element and an excitation light output device. B is a configuration diagram illustrating a side configuration of an example of the beam combining element. FIG. 4 is an explanatory diagram of a polarization mode of an example of a phase difference section. FIG. 4 is an explanatory diagram of a polarization mode of an example of a phase difference section. FIG. 4 is an explanatory diagram of a polarization mode of an example of a phase difference section. It is a block diagram of an example of a beam multiplexing element. It is explanatory drawing of an example of a beam combining mode. It is explanatory drawing of an example of a beam combining mode. It is explanatory drawing of an example of a beam multiplexing element. It is a block diagram of an example of a beam multiplexing element. It is a block diagram of an example of a beam multiplexing element. It is a block diagram of an example of a beam multiplexing element. It is a block diagram of an example of a beam multiplexing element. It is a block diagram of an example of a beam separation element.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Birefringent material part 1A Incident end face 1B Outgoing end face 2 Phase difference part 3 Auxiliary phase difference part 4 Light source 5 Optical system 6 Optical system 7 Fiber 8 Optical system 9 Lens 10 Beam combining element 11 Lens 12 Optical system 20 Beam separating element 21 Phase difference part 22 Phase difference part 31 Auxiliary phase difference part 32 Auxiliary phase difference part 41 Birefringent material part 41A1 Incident end face 41A2 Incident end face 41B Exit end face 42 Birefringent material part 42A Incident end face 42B Exit end face 50 Excitation light output device 60 Optical element 70 Wavelength conversion element

Claims (25)

At least a birefringent material portion, comprising a retardation portion fixedly arranged at least a part of the beam incident end face of the birefringent material portion,
First and second beams or groups of beams whose propagation directions are substantially parallel and have substantially the same polarization are incident on the birefringent material portion,
At least one beam or beam group of the first or second beam or beam group is incident on the birefringent material portion via the phase difference portion, and the polarization direction is changed by the phase difference portion. ,
At least one beam or beam group of the first and second beams or beam groups is changed in a propagation direction in the birefringent material portion,
A beam multiplexing element, wherein the first and second beams or beam groups are multiplexed at an emission position of the birefringent material portion or an emission or incidence interface and emitted in substantially the same direction. The beam combining element according to claim 1, wherein the phase difference part is a half-wave plate. 2. The beam multiplexing device according to claim 1, wherein the phase difference portion is bonded to the beam incident end face of the birefringent material portion. The beam combining element according to claim 1, wherein the phase difference part and the birefringent material part are made of the same material. An auxiliary retardation portion is arranged on the beam incident end face of the birefringent material portion in parallel with the retardation portion,
A beam or a group of beams not incident on the phase difference portion is incident on the auxiliary phase difference portion, and the polarization direction thereof is not converted before and after passing through the auxiliary phase difference portion. The beam combining element according to claim 1. The beam combining element according to claim 5, wherein the phase difference part and the auxiliary phase difference part are made of the same material. The beam multiplexing device according to claim 5, wherein the physical lengths of the first and second beams or the beam groups in the phase difference part and the auxiliary phase difference part are substantially equal to each other. The beam combining element according to claim 5, wherein the auxiliary phase difference part is made of a material having optical isotropy or a transmission plate. 2. The beam combining device according to claim 1, wherein an optical film having an antireflection function is formed on at least one or more incident end faces and / or outgoing end faces of the retardation section and / or the birefringent material section. 3. Wave element. 6. The beam combining element according to claim 5, wherein an optical film having an antireflection function is formed on the incident end face and / or the output end face of the auxiliary retardation section. 2. The beam multiplexing device according to claim 1, wherein the beam incident on said beam multiplexing device is laser diode light. Before and / or after the beam multiplexing element, the divergence angle of the first and second beams or the beam group is reduced, converted to a collimated beam, or collected. 2. The beam multiplexing device according to claim 1, further comprising an optical system having at least one action. 13. The beam multiplexing device according to claim 12, wherein a lens is formed on the incident end face and / or the output end face of the phase difference portion and / or the birefringent material portion. 2. The beam multiplexing device according to claim 1, wherein the phase difference portion is formed of a phase delay film. 2. The beam multiplexing device according to claim 1, wherein the birefringent material portion includes two or more birefringent elements. The material of the birefringent material _{part, KTiOPO 4, RbTiOPO 4, RbTiOAsO} 4, KTiOAsO 4, LiNbO 3, LiTaO 3, MgO -doped LiNbO _3, MgO-doped _{LiTaO 3, KNbO 3, BaTiO 3} , Ba 2 NaNb 5 O 15, _{SrBaNbO 7, KH 2 PO 4,} KD 2 PO 4, BaB 2 O 4, LiB 3 O 5, LiB 4 O 7, CsLiB 6 O 10, CsB 3 O 5, SiO 2, TiO 2, YVO 4, calcite, MgF _2. The beam multiplexing device according to claim 1, wherein a single crystal of one of CaF ₂ and α-Al ₂ O ₃ or a eutectic of each of the above materials is used. Using at least a birefringent material portion and a phase difference portion fixedly arranged on at least a part of the beam incident end face of the birefringent material portion,
First and second beams or a group of beams whose propagation directions are substantially parallel and have substantially the same polarization are made incident on the birefringent material portion,
At least one beam or beam group of the first or second beam or beam group is incident on the birefringent material portion through the phase difference portion, and the polarization direction is changed by the phase difference portion,
By changing the propagation direction of the at least one beam or beam group of the first or second beam or beam group in the birefringent material portion,
A beam multiplexing method, wherein the first and second beams or groups of beams are multiplexed at an emission position of the birefringent material section or an emission or incidence interface and emitted in substantially the same direction. The beam combining method according to claim 17, wherein the phase difference unit is a half-wave plate. 18. The beam multiplexing method according to claim 17, wherein the phase difference portion is formed by adhering to the beam incident end face of the birefringent material portion.   The beam combining method according to claim 17, wherein the phase difference part is made of the same material as the birefringent material part. The auxiliary retardation portion is arranged on the beam incident end face of the birefringent material portion in parallel with the retardation portion,
A beam or a beam group of the first and second beams or the beam group, which is not incident on the phase difference unit, is incident on the auxiliary phase difference unit, and its polarization direction is converted before and after transmission through the auxiliary phase difference unit. 18. The beam combining method according to claim 17, wherein the beam combining method is not performed. At least a birefringent material portion, comprising a retardation portion fixedly arranged at least a part of the beam exit end face of the birefringent material portion,
In the birefringent material portion, the propagation direction of the specific polarization direction component of the incident beam is changed, and the light is separated and emitted as first and second beams or beam groups having different polarizations,
When the polarization direction of at least one of the first and second beams or the beam group is changed by the phase difference unit, the first and second beams or the beam group are changed in the propagation direction. Are substantially parallel and are emitted as two beams or a group of beams having substantially the same polarization direction. Using at least a birefringent material portion and a phase difference portion fixedly disposed on at least a part of the beam exit end face of the birefringent material portion,
In the birefringent material section, the direction of propagation of the specific polarization direction component of the incident beam is changed, and the light is separated and emitted as first and second beams or beam groups having mutually different polarizations,
By changing the polarization direction of at least one of the first and second beams or the beam group by the phase difference unit, the propagation direction of the first and second beams or the beam group is changed. A beam separation method for emitting two beams that are substantially parallel and have substantially the same polarization direction. The first and second beams or groups of beams whose propagation directions are substantially parallel and have substantially the same polarization have at least a birefringent material portion and a phase difference portion fixed to at least a part of the beam incident end face of the birefringent material portion. Incident on the arranged beam combining element,
At least one beam or beam group of the first and second beams or beam groups is incident on the birefringent material part via the phase difference part, and the polarization direction is changed by the phase difference part,
At least one beam or beam group of the first or second beam or beam group, the propagation direction in the birefringent material portion is changed,
The first and second beams or a group of beams are combined at the emission position of the birefringent material section or at the emission or incidence interface, emitted in substantially the same direction, and emitted as laser excitation light. An excitation light output device characterized by the above-mentioned. The pump light output device according to claim 24, wherein the laser is a fiber amplifier laser or a fiber laser.

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