JP5614638B2 - Solid state laser - Google Patents

Description

  The present invention relates to a solid-state laser that generates pump light based on pumping light output from a pumping light source, amplifies it by a resonator, and outputs laser light having a wavelength different from that of pumping light. The present invention relates to a solid-state laser that can generate pumped light.

Conventionally, pump light output from a pump light source is input to a laser crystal made of, for example, Nd: YVO ₄ (neodymium-doped yttrium vanadate) to generate pump light, and the pump light is amplified by a resonator. Solid-state lasers that output in the past are known. In this type of solid-state laser, a resonator is generally formed by a laser crystal and reflecting mirrors arranged opposite to each other with the laser crystal interposed therebetween, and pump light is amplified and output by this resonator. It is configured as follows. In a solid-state laser having this type of resonator, when the pump light is resonated by the resonator, a plurality of longitudinal modes are generated at predetermined frequency intervals (hereinafter referred to as “vertical multimode conversion”). Since the quality of the laser beam deteriorates, various improvements for suppressing this vertical multimode have been made.

  An example of a solid-state laser that has been improved to suppress this type of longitudinal multimode is described in Patent Document 1. The solid-state laser described in Patent Document 1 includes a laser crystal and a resonator mirror that is disposed so as to face the laser crystal and reflects pump light from the laser crystal, and is pumped by the resonator mirror and the laser crystal. In this configuration, a resonator for resonating light is formed, and an etalon plate is provided in the resonator, whereby pump light is converted into a single longitudinal mode. As described above, the solid-state laser described in Patent Document 1 includes a laser crystal, a resonator mirror, and an etalon plate, and generates single longitudinal mode pump light.

JP 2002-314181 A

  However, the solid-state laser described in Patent Document 1 has a configuration in which an etalon plate is provided in addition to a laser crystal and a resonator mirror, so that the structure is complicated and there is a problem that it is not suitable for miniaturization. In addition, it is necessary to adjust the inclination of the etalon plate with respect to the laser crystal and the resonator mirror in order to make the pump light into a single longitudinal mode, and there is a problem that adjustment work takes time.

  Therefore, the present invention has been made paying attention to the above problems, and can generate pump light in a single longitudinal mode with a structure that is simple and suitable for miniaturization and that has a simple adjustment work. An object is to provide a solid-state laser.

In order to achieve the above object, a solid-state laser according to an aspect of the present invention includes a laser crystal that generates pump light by excitation light , and a resonator mirror that is disposed opposite to the laser crystal so as to face the pump light. a first resonator for resonating at the first resonator, a second resonator for resonating portion of the pump light is resonated in the first resonator between end faces of the resonator mirror, the provided, in which a configuration for matching the laser crystal and the Geinpi over clock frequency of the first resonator arrangement position adjusted to the resonator mirror of the second resonator gain peak frequency.
In order to achieve the above object, a solid-state laser according to another aspect of the present invention generates pump light based on excitation light , amplifies it with a resonator, and outputs laser light having a wavelength different from that of the excitation light. in solid-state laser, a laser over the crystal that generates the pump light by an input of the excitation light, wherein arranged between the light source of the excitation light and the laser crystal, the pumping light generated in the laser crystal, the laser crystals And a resonator mirror that reflects on the opposite end face, and is disposed opposite to the resonator mirror with the laser crystal interposed therebetween , and pump light whose output intensity is a predetermined threshold value or more is a wavelength of the pump light. converted into a different signal light and the idler light, and a wavelength conversion element which outputs the idler light to the outside portion, a first for resonating the pump light generated from said laser crystal The oscillator, the the laser crystal formed in the end face opposite the end face opposite to said laser crystal of the resonator mirror, a portion of the pump light is resonated in the first resonator of the wavelength conversion element a second resonator for resonating the opposite side of the end face and the resonator mirror formed on the end face of the laser crystal side, the resonator mirror and the front Symbol wavelength converting element and the laser Heather crystal of the resonator mirrors the position adjustment to the a configuration to match the gain peak frequency of the second resonator gain peak frequency of the first resonator, are output from the second cavity, the output intensity is not smaller than a predetermined threshold value Based on single longitudinal mode pump light, the wavelength conversion element outputs the idler light to the outside.

With this configuration, the solid-state laser according to the above one aspect, a laser crystal that occurs the pump light by the excitation light, in the resonator mirrors disposed to face each other apart from the the laser crystals, generated in the laser crystal pump The first resonator for resonating light is configured, and the arrangement positions of the laser crystal and the resonator mirror are adjusted to obtain the gain peak frequency of the first resonator and the gain peak of the second resonator in the first resonator . The frequencies are matched.
Further, the solid-state laser according to the above-described another aspect constitutes a first resonator that resonates pump light generated in a laser crystal by a resonator mirror and a wavelength conversion element that is disposed opposite to the resonator mirror. In addition, the arrangement positions of the wavelength conversion element and the resonator mirror are adjusted so that the gain peak frequency of the first resonator matches the gain peak frequency of the second resonator in the first resonator .

According to the solid-state laser of the present invention , the first and second resonators are configured by the laser crystal and the resonator mirror , or by the wavelength conversion element and the resonator mirror, and the pump light of the single longitudinal mode is generated. Since output is possible, an etalon plate is not required, the structure can be simplified as compared with a conventional solid-state laser, and the length of the resonator can be reduced and the size can be reduced. In addition, since the number of components constituting the resonator is reduced, the adjustment work such as the inclination between the components can be reduced as compared with the conventional solid-state laser. Then, the pump light in the single longitudinal mode can be generated by matching the gain peak frequency of the first resonator with the gain peak frequency of the second resonator . In this way, it is possible to provide a solid-state laser capable of generating pump light in a single longitudinal mode with a structure that is simple and suitable for miniaturization, and that has a simple adjustment work.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing of 1st Embodiment of the solid-state laser which concerns on this invention, (a) is a schematic block diagram, (b) is description explaining an example of the main wavelengths of the laser beam in each area in the solid-state laser of this embodiment. FIG. It is a figure which shows the frequency distribution characteristic of the pump light output from the laser crystal in the said embodiment. It is a figure which shows the reflectance with respect to the laser beam of each wavelength in each end surface of the said embodiment. In the said embodiment, it is a figure explaining the condition where pump light turns into single longitudinal mode, (a) becomes longitudinal multimode in a 1st resonator, (b) becomes longitudinal multimode in a 2nd resonator, (C) is a conceptual diagram showing a single longitudinal mode of pump light. It is an operation | movement flowchart explaining the operation | movement which the solid laser of the said embodiment outputs the pump light of a single longitudinal mode. It is explanatory drawing of 2nd Embodiment of the solid-state laser which concerns on this invention, (a) is a schematic block diagram, (b) is description which shows an example of the main wavelengths of the laser beam in each area in the solid-state laser of this embodiment. FIG. It is a figure which shows the reflectance with respect to the laser beam of each wavelength in each end surface of the said embodiment. It is explanatory drawing of 3rd Embodiment of the solid-state laser which concerns on this invention, (a) is a schematic block diagram, (b) is description explaining an example of the main wavelengths of the laser beam in each area in the solid-state laser of this embodiment. FIG. It is a figure which shows the reflectance with respect to the laser beam of each wavelength in each end surface of the said embodiment. It is explanatory drawing of 4th Embodiment of the solid-state laser which concerns on this invention, (a) is a schematic block diagram, (b) is description which shows an example of the main wavelengths of the laser beam in each area in the solid-state laser of this embodiment. FIG. It is a figure which shows the reflectance with respect to the laser beam of each wavelength in each end surface of the said embodiment. It is explanatory drawing of 5th Embodiment of the solid-state laser which concerns on this invention, (a) is a schematic block diagram, (b) is description which shows an example of the main wavelengths of the laser beam in each area in the solid-state laser of this embodiment. FIG. It is a figure which shows the reflectance with respect to the laser beam of each wavelength in each end surface of the said embodiment. It is explanatory drawing of 6th Embodiment of the solid-state laser which concerns on this invention, (a) is a schematic block diagram, (b) is description which shows an example of the main wavelengths of the laser beam in each area in the solid-state laser of this embodiment. FIG. It is a figure which shows the reflectance with respect to the laser beam of each wavelength in each end surface of the said embodiment.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
Fig.1 (a) is a schematic block diagram which shows 1st Embodiment of the solid-state laser 1 which concerns on this invention. FIG.1 (b) is explanatory drawing which shows an example of the main wavelength of the laser beam in each area of the solid-state laser 1 in this embodiment.
In FIG. 1A, the solid-state laser 1 of this embodiment amplifies pump light generated from a laser crystal 4 to be described later excited by excitation light output from an excitation light source 2, and has a wavelength different from that of the excitation light. A laser beam is output and includes an excitation light source 2, a condenser lens 3, a laser crystal 4, and a resonator mirror 5. The laser resonator 4 and the resonator mirror 5 form a first resonator 6. The second resonator 7 is formed by the resonator mirror 5. Further, in FIG. 1A, the broken line indicates the optical path of the excitation light, and the dotted line indicates the optical path of the pump light, and indicates a situation in which the pump light is output to the outside.

  The excitation light source 2 generates laser light and is, for example, a commercially available laser light source. The laser light emitted from the excitation light source 2 becomes excitation light for exciting a laser crystal 4 described later. The wavelength (λ0) of the excitation light emitted from the excitation light source 2 is, for example, about 808 nm. The excitation light having a wavelength of about 808 nm mainly exists in the section shown in FIG.

  The condensing lens 3 is a lens configured to condense the excitation light emitted from the excitation light source 2 at substantially the center of the laser crystal 4 as indicated by a broken line in FIG.

The laser crystal 4 generates pump light when excitation light is input. In the present embodiment, the laser crystal 4 is disposed between the excitation light source 2 and the resonator mirror 5 as shown in FIG. The crystal used as the laser crystal 4 is, for example, Nd: YVO ₄ (neodymium-added yttrium vanadate), and in this case, the pump light generated in the laser crystal 4 by the input of excitation light having a wavelength (λ0) of about 808 nm. The wavelength (λp) indicating the gain peak is, for example, about 1064 nm. As shown in FIG. 2, the pump light generated from the laser crystal 4 has a characteristic in which gain (output intensity) is distributed in a wide frequency band around the gain peak frequency fm1 (wavelength of about 1064 nm) of the laser crystal 4. Indicates. Further, the pump light having the gain peak frequency fm1 (wavelength of about 1064 nm) mainly includes a section between an end face S1 and an end face S4, which will be described later, and a section between the end face S3 and the end face S4, as shown in FIG. Exists.

  In the present embodiment, the laser crystal 4 is formed such that the end surface S1 opposite to the resonator mirror 5 is substantially transmitted (low reflection) with respect to the excitation light and substantially reflected (high reflection) with respect to the pump light. The end face S2 on the resonator mirror side is formed so that the pump light is substantially transmitted (low reflection). For example, the reflectance for the laser light of each wavelength at the end face S1 and the end face S2 is set as shown in FIG. 3 to be described later by applying an appropriate coating to each end face.

  The resonator mirror 5 is disposed so as to face the laser crystal 4 and reflects the pump light generated by the laser crystal 4 at the end surface S4 opposite to the laser crystal 4, for example, a general glass Etc., and becomes a reflecting mirror for the first resonator 6 and the second resonator 7 which will be described later. In the present embodiment, the resonator mirror 5 is disposed to face the excitation light source 2 with the laser crystal 4 interposed therebetween, as shown in FIG.

  In this embodiment, the resonator mirror 5 is formed such that the end surface S4 on the side opposite to the laser crystal 4 is substantially reflected (highly reflected) with respect to the pump light, and the end surface S3 on the laser crystal 4 side is formed on the laser crystal. 4 is formed such that a part of the pump light reflected by the end surface S4 on the opposite side to 4 is reflected (partially reflected). For example, the reflectance with respect to the laser light of each wavelength at the end face S3 and the end face S4 is set as shown in FIG. 3 by applying an appropriate coating to each end face. In FIG. 3, AR indicates a low reflectance (for example, less than 1%), that is, indicates that laser light having a corresponding wavelength is substantially transmitted to substantially prevent reflection, and HR is a high reflectance. (For example, 95% or more and less than 100%), that is, indicates that the laser beam of the corresponding wavelength is almost reflected, and PR is a reflectance between the low reflectance and the high reflectance (for example, several%). That is, it indicates that a part (for example, several%) of the laser beam having the corresponding wavelength is reflected (partially reflected), and a part not described in the figure corresponds to the laser beam having the corresponding wavelength at the end face. The coating is not applied.

  In this embodiment, the resonator mirror 5 is formed so that the end surface S3 on the laser crystal 4 side has a planar shape and the end surface S4 on the opposite side to the laser crystal 4 has a convex shape. Thereby, the pump light reflected by the end surface S4 can be reflected toward the end surface S1. Therefore, since the pump light can be reflected without leaking to the outside, efficient resonance of the pump light can be easily performed. In the resonator mirror 5, the end surface S3 on the laser crystal 4 side has a planar shape, and the end surface S4 opposite to the laser crystal 4 has a convex shape. However, the present invention is not limited to this, and the end surface S3 and the end surface are not limited thereto. Both S4 may have a planar shape. Even in this case, the pump light can be reflected without leaking to the outside by, for example, adjusting the inclination of the resonator mirror 5 and the laser crystal 4 with high accuracy.

  The first resonator 6 resonates the pump light generated from the laser crystal 4, and the end surface S 1 of the laser crystal 4 opposite to the resonator mirror 5 and the laser crystal 4 of the resonator mirror 5 opposite to the laser crystal 4. The end surface S4 is formed.

Generally, in resonance in a laser resonator such as the first resonator 6 or the second resonator 7, a plurality of longitudinal modes exist at predetermined frequency intervals around the gain peak frequency fm of the laser crystal (longitudinal multimode). ). The frequency interval is referred to as a longitudinal spectral interval (FSR). Generally, the longitudinal mode interval is C for the speed of light, n for the refractive index in the optical path, and d for the resonator length of the resonator. Then, it is determined by the following equation (1).
FSR = C / (2nd) (1)

FIG. 4A shows a plurality of pump light beams output from the laser crystal 4 at a predetermined frequency interval centered on the gain peak frequency fm1 (wavelength: about 1064 nm) of the laser crystal 4 when the first resonator 6 resonates. This shows the situation in which the vertical mode occurred. In FIG. 4 (a), FIG. 4 (b) and FIG. 4 (c), which will be described later, each longitudinal mode is represented by a single line for simplification of the drawing. Has a line width as indicated by a broken line. Here, when the resonator length of the first resonator 6 is d ₁ (see FIG. 1A) and the refractive index is n ₁ , the longitudinal mode interval FSR1 of the first resonator 6 is the following (2). Determined by the formula.
FSR1 = C / (2n ₁ d ₁ ) (2)
D ₁ is the distance between the end surface S 1 and the end surface S 4, and n ₁ is a refractive index that is determined in combination by the materials in the end surfaces S _{1 to} S 4. In the present embodiment, the thickness of the laser crystal 4 and the resonator mirror 5, thinner negligibly with respect to the distance between the end surface S2 and the end face S3, the refractive index n ₁ of the first resonator, the refractive index of air Is almost equal.

  The second resonator 7 resonates a part of the pump light resonated by the first resonator 6, and the end face S 3 of the resonator mirror 5 on the laser crystal 4 side, the laser crystal 4 of the resonator mirror 5, and Is formed by the opposite end face S4.

FIG. 4B shows that when a part of the pump light resonated by the first resonator 6 is resonated by the second resonator 7, a plurality of longitudinal modes are generated at a predetermined frequency interval with the gain peak frequency fm2 as the center. Indicates the situation that occurred. In this case, when the resonator length of the second resonator 7 is d ₂ (see FIG. 1A) and the refractive index is n ₂ , the longitudinal mode interval FSR2 of the second resonator 7 is the following (3). Determined by the formula.
FSR2 = C / (2n ₂ d ₂ ) (3)
D ₂ is the thickness between the end face S 3 and the end face S 4 of the resonator mirror 5, which is extremely small compared to d ₁ , for example, several hundred μm. N ₂ is a value determined by the material of the resonator mirror 5.

Further, as can be seen from FIGS. 4A and 4B, the second resonator 7 has a frequency band width in which the longitudinal mode interval FSR2 of the second resonator 7 can resonate within the first resonator 6. The refractive index n ₂ and the resonator length d ₂ are set so as to be larger than approximately half the value of fw (fw / 2). The frequency of the longitudinal mode with the highest gain in the second resonator 7 manufactured in this way (that is, the gain peak frequency fm2) and the frequency of the longitudinal mode with the highest gain in the first resonator 6 (gain as the peak frequency fm1) and coincides, for example, to modify the cavity length d ₁ of the first resonator 6 by adjusting the position of the resonator mirror 5 and the laser crystal 4, the first resonator 6 The frequency fm1 of the longitudinal mode with the highest gain at is finely adjusted.

Next, an operation in which the solid-state laser 1 according to the first embodiment configured as described above outputs pump light in a single longitudinal mode to the outside will be described with reference to an operation flowchart shown in FIG. As shown in the schematic diagram below FIG. 4C, the longitudinal mode interval FSR1 of the second resonator 7 is set to be larger than almost half of the frequency bandwidth fw that can resonate in the first resonator 6. The resonator of the first resonator 6 manufactured in advance so that the frequency of the longitudinal mode having the highest gain in the first resonator 6 and the frequency of the longitudinal mode having the highest gain in the second resonator 7 coincide with each other. hereinafter described as the length d ₁ is finely adjusted in advance. Further, the pump light output from the laser crystal 4 propagates toward the end surface S3, and a part (several percent) of the pump light is reflected at the end surface S3 and propagates toward the end surface S1 to be amplified. In addition to the first resonator 6 and the second resonator 7, there is also a resonator formed by the end surface S1 and the end surface S3, but the resonator does not directly contribute to the conversion of the pump light into a single longitudinal mode. Therefore, in the following description, the description of the resonance operation of the pump light between the end surface S1 and the end surface S3 is omitted.

  First, as shown in FIGS. 1A and 1B, excitation light having a wavelength λ 0 of about 808 nm is output from the excitation light source 2 (STEP 1). Then, the excitation light is condensed at the center of the laser crystal 4 by the condenser lens 3 (STEP 2). The excitation light passes through the end face S1 and is input into the laser crystal 4, and as shown in FIG. 2, pump light having a wavelength λp indicating a gain peak of about 1064 nm is output from the laser crystal 4 (STEP 3). The output pump light propagates toward the end surface S3, and the pump light transmitted through the end surface S3 propagates through the resonator mirror 5 toward the end surface S4 and is reflected by the end surface S4. The reflected pump light propagates toward the end surface S3 and is amplified. Further, the pump light transmitted through the end surface S3 among the amplified pump light is propagated toward the end surface S1 and amplified. , Is transmitted through the end surface S2 and reflected by the end surface S1. In this way, when the pump light is resonated by the first resonator 6 formed by the end face S1 and the end face S4, a plurality of longitudinal modes are generated as shown in FIG. 4A (STEP 4). In STEP 4, a part (several percent) of the pump light reflected by the end face S4 and propagating toward the end face S1 (that is, pump light resonated by the first resonator 6) is reflected by the end face S3, and the end face It propagates toward S4, is reflected at the end face S4, propagates toward the end face S3, and is amplified. In this way, when part of the pump light resonated by the first resonator 6 is resonated by the second resonator 7 formed by the end surface S3 and the end surface S4, as shown in FIG. The vertical mode is generated (STEP 5). As in STEP 4 and STEP 5 described above, in the state where the pump light is resonated, the frequency of the longitudinal mode with the highest gain in the first resonator 6 and the frequency of the longitudinal mode with the highest gain in the second resonator 7 And the second resonator 7 outputs pump light of a single longitudinal mode as shown in FIG. 4C to the outside.

  With such a configuration, the laser crystal 4 and the resonator mirror 5 constituting the first resonator 6 and the second resonator 7 can output pump light in a single longitudinal mode, so an etalon plate is necessary. Compared with the conventional solid-state laser, the structure can be simplified, and the length of the resonator can be shortened to reduce the size. In addition, since the number of components constituting the resonator is reduced, the adjustment work such as the inclination between the components can be reduced as compared with the conventional solid-state laser. In this way, it is possible to provide a solid-state laser capable of generating pump light in a single longitudinal mode with a structure that is simple and suitable for miniaturization, and that has a simple adjustment work.

  FIG. 6A is a schematic configuration diagram showing a second embodiment of the solid-state laser 1 according to the present invention, in which a broken line indicates an optical path of excitation light, a dotted line indicates an optical path of pump light, and pump light is output to the outside. Shows the situation. FIG. 6B is a diagram illustrating an example of main wavelengths of laser light propagating in each section. In addition, the same code | symbol is attached | subjected to the element same as 1st Embodiment of FIG. 1, description is abbreviate | omitted, and only a different part is demonstrated.

  In the present embodiment, as shown in FIG. 6A, the laser crystal 4 is disposed so as to face the excitation light source 2 with the resonator mirror 5 interposed therebetween. Further, pump light having a gain peak frequency fm1 (wavelength of about 1064 nm) output from the laser crystal 4 mainly includes a section between the end face S1 and the end face S4, an end face S3, and an end face as shown in FIG. It exists in the section between S4.

  In the present embodiment, the laser crystal 4 is formed such that the end face S2 on the side of the resonator mirror 5 is substantially transmitted (low reflection) with respect to the excitation light and the pump light, and the end face S1 on the side opposite to the resonator mirror 5 is formed. The pump light is formed so as to be substantially reflected (highly reflected). The resonator mirror 5 is formed so that the end surface S4 opposite to the laser crystal 4 is substantially transmitted (low reflection) with respect to the excitation light and substantially reflected (high reflection) with respect to the pump light. The end surface S3 on the 4 side is formed so that the excitation light is almost transmitted (low reflection), and a part of the pump light reflected by the end surface S4 opposite to the laser crystal 4 is reflected (partial reflection). Yes. For example, the reflectivity of each end face (S1 to S4) with respect to each wavelength of laser light is set as shown in FIG. 7 by applying an appropriate coating to each end face. Note that AR, HR, and PR shown in FIG. 7 indicate the same contents as the reflectance described in FIG.

  The operation of the solid-state laser 1 of the second embodiment configured as described above outputting pump light in a single longitudinal mode to the outside is that the excitation light is input from the end surface S2 side of the laser crystal 4. Since it is the same as 1st Embodiment, description is abbreviate | omitted.

  With this configuration, in the present embodiment as well, as in the first embodiment, the pump crystal of the single longitudinal mode can be output by the laser crystal 4 and the resonator mirror 5, so that the conventional solid-state laser can be output. The structure can be simplified compared to the above, and the length of the resonator can be shortened to reduce the size. Furthermore, it is possible to simplify the adjustment work such as the inclination between the components.

Hereinafter, a configuration example will be described in which a wavelength conversion element is provided and idler light having a wavelength in the middle infrared region, for example, is output to the outside.
FIG. 8A is a schematic configuration diagram illustrating a third embodiment of the solid-state laser 1 according to the present invention, in which a broken line indicates an optical path of excitation light, and a dotted line indicates an optical path of laser light having a wavelength different from that of the excitation light. This shows the situation where idler light is output to the outside. FIG. 8B is a diagram illustrating an example of main wavelengths of laser light propagating in each section. In addition, the same code | symbol is attached | subjected to the element same as 1st Embodiment of FIG. 1, description is abbreviate | omitted, and only a different part is demonstrated.

  In the solid-state laser 1 in the present embodiment, as shown in FIG. 8A, the wavelength conversion element 8 is disposed between the laser crystal 4 and the resonator mirror 5.

When the pump light (wavelength λp) having an output intensity equal to or greater than a predetermined threshold is incident, the wavelength conversion element 8 converts part of the pump light into signal light (wavelength λs) and idler light (wavelength different from the pump light). λi), and is made of a ferroelectric crystal having a domain-inverted structure. Further, the magnitude relationship between the wavelengths is λp <λs <λi, which satisfies the following expression (4).
1 / λp = 1 / λs + 1 / λi (4)

In this embodiment, the wavelength conversion element 8 uses, for example, lithium niobate LiNbO ₃ (PPLN: Periodically-Poled LN) having a polarization inversion structure. In this case, in the wavelength conversion element 8, the wavelength (λs) of the signal light converted from the pump light having the wavelength (λp) of about 1064 nm is, for example, about 1384 nm. As shown in FIG. 8B, the signal having a wavelength of about 1384 nm mainly exists in a section between the end surface S5 and the end surface S6. Similarly, the wavelength (λi) of idler light that is wavelength-converted from pump light is, for example, about 4610 nm. As shown in FIG. 8B, the idler light having a wavelength of about 4610 nm is generated from the wavelength conversion element 8, propagates toward the end face S4, passes through the end face S4, and is output to the outside. Thus, the wavelength conversion element 8 outputs laser light having a wavelength in the mid-infrared region (3 to 5 μm), for example.

  The wavelength conversion element 8 is formed such that the end face S5 on the laser crystal 4 side is substantially transmitted (low reflection) with respect to the pump light and substantially reflected (high reflection) with respect to the signal light. The opposite end face S6 is formed so as to be substantially transmissive (low reflection) for pump light, substantially reflected (high reflection) for signal light, and substantially transmissive (low reflection) for idler light. In the present embodiment, the resonator mirror 5 is formed so that the idler light is almost transmitted through the end surface S3 on the laser crystal 4 side and the end surface S4 on the opposite side to the laser crystal 4. The reflection and transmission characteristics of each wavelength other than the above for the laser light of each wavelength are the same as in the first embodiment. For example, the reflectance for the laser light of each wavelength on each end surface (S1 to S6) By applying an appropriate coating, the setting is made as shown in FIG. Note that AR, HR, and PR shown in FIG. 9 indicate the same contents as the reflectance described in FIG.

Next, regarding the operation in which the solid-state laser 1 of the third embodiment configured as described above outputs idler light to the outside, for example, the wavelength conversion element 8 is lithium niobate LiNbO ₃ (PPLN: Periodically-Poled LN). The case where the wavelength of the target idler light is 4610 nm will be described as an example. Note that the operation for generating pump light in a single longitudinal mode from the second resonator 7 is the same as that in the first embodiment, and therefore the description is simplified.

  First, as shown in FIGS. 8A and 8B, excitation light from the excitation light source 2 is input to the laser crystal 4, and pump light is output from the laser crystal 4. The output value of the pump light is suppressed so that the output intensity of the pump light output from the laser crystal 4 is, for example, less than the oscillation threshold value of the wavelength conversion element 8 in order to suppress power consumption. Then, the pump light having an output below the oscillation threshold passes through the wavelength conversion element 8 and propagates toward the end face S4 of the resonator mirror 5. Then, the pump light is reflected by the end surface S4, and is amplified by the first resonator 6 and the second resonator 7 in the same manner as in the first embodiment, and is converted into a single longitudinal mode. For example, pump light generated from the laser crystal 4 is reflected by the end face S4, and among the pump light, pump light that has passed through the end face S3 propagates toward the end face S1, passes through the wavelength conversion element 8, and passes through the end face S1. , And the output intensity of the pump light is amplified to be equal to or greater than the oscillation threshold value of the wavelength conversion element 8. Next, the pump light amplified to an output intensity equal to or higher than the oscillation threshold and converted into a single longitudinal mode is reflected by the end face S1, is input to the wavelength conversion element 8, and is determined based on the wavelength conversion element 8 ( 4) Conversion into signal light and idler light having a wavelength satisfying the equation. The idler light passes through the end surface S4 and is output to the outside. Further, the signal light resonates between the end surface S5 and the end surface S6. In the above description, the case where the output intensity of the pump light is amplified to be equal to or higher than the oscillation threshold value of the wavelength conversion element 8 when the pump light reciprocates once in the first resonator 4 has been described. You may reciprocate multiple times until the threshold is reached.

  With such a configuration, it is possible to input single longitudinal mode pump light to the general wavelength conversion element 8 and perform wavelength conversion, so that high-quality idler light can be output. In this way, as in the first embodiment, the structure is simple, suitable for downsizing, and the adjustment work is simple, and pump light in a single longitudinal mode can be generated, and the quality is high. For example, it is possible to provide a solid-state laser capable of outputting laser light having a wavelength in the mid-infrared region. In addition, the first resonator 6 can increase the intensity of the pump light output from the laser crystal 4 to an output that is equal to or higher than the oscillation threshold value of the wavelength conversion element 8. Power consumption can be suppressed by driving. Further, in the present embodiment, since the signal light can resonate between the end face S5 and the end face S6 of the wavelength conversion element 8, the oscillation threshold of the wavelength conversion element 8 is set to the signal light as conventionally known. Therefore, power consumption can be further suppressed.

  FIG. 10A is a schematic configuration diagram showing a fourth embodiment of the solid-state laser 1 according to the present invention, where a broken line indicates an optical path of excitation light, and a dotted line indicates an optical path of laser light having a wavelength different from that of the excitation light. This shows the situation where idler light is output to the outside. FIG. 10B is a diagram illustrating an example of main wavelengths of laser light propagating in each section. In addition, the same code | symbol is attached | subjected to the element same as 3rd Embodiment of FIG. 8, description is abbreviate | omitted, and only a different part is demonstrated.

  In the present embodiment, the wavelength conversion element 8 is disposed so as to face the laser crystal 4 with the resonator mirror 5 interposed therebetween, as shown in FIG. In the case of the present embodiment, unlike the resonator mirror 5 in the third embodiment, it is not necessary to apply a low-reflective coating to the end surface S5 and the end surface S6 on the end surfaces (S1 to S6). The reflectance with respect to the laser light of each wavelength is set as shown in FIG.

  Even with such a configuration, the pump light in a single longitudinal mode can be input to the wavelength conversion element 8 for wavelength conversion. Therefore, as in the third embodiment, the structure is simple and suitable for downsizing, and A solid laser capable of generating pump light in a single longitudinal mode with a simple adjustment work and capable of outputting high-quality idler light can be provided. Similarly to the third embodiment, the pump light is amplified by the first resonator 6 and the signal light is amplified by the end face S5 and the end face S6, thereby suppressing the output of the excitation light and driving the excitation light source 2. Power consumption can be suppressed.

  FIG. 12A is a schematic configuration diagram showing a fifth embodiment of the solid-state laser 1 according to the present invention, in which a broken line indicates an optical path of excitation light, and a dotted line indicates an optical path of laser light having a wavelength different from that of the excitation light. This shows the situation where idler light is output to the outside. FIG. 12B is a diagram illustrating an example of main wavelengths of laser light propagating in each section. In addition, the same code | symbol is attached | subjected to the element same as 2nd Embodiment of FIG. 6, description is abbreviate | omitted, and only a different part is demonstrated.

  In this embodiment, as shown in FIG. 12A, the wavelength conversion element 8 is disposed to face the resonator mirror 5 with the laser crystal 4 interposed therebetween. Moreover, the reflectance with respect to the laser beam of each wavelength in each end surface (S1-S6) is set as shown in FIG.

  Even with such a configuration, the structure is simple, suitable for downsizing, and the adjustment work is simple, and pump light in a single longitudinal mode can be generated, and high-quality idler light is output. It is possible to provide a solid-state laser capable. Further, similarly to the third embodiment, it is possible to suppress the power consumption by driving the excitation light source 2 while suppressing the output of the excitation light.

  FIG. 14A is a schematic configuration diagram showing a sixth embodiment of the solid-state laser 1 according to the present invention, in which a broken line indicates an optical path of excitation light, and a dotted line indicates an optical path of laser light having a wavelength different from that of the excitation light. This shows the situation where idler light is output to the outside. FIG. 14B is a diagram illustrating an example of main wavelengths of laser light propagating in each section. In addition, the same code | symbol is attached | subjected to the element same as 5th Embodiment of FIG. 12, description is abbreviate | omitted, and only a different part is demonstrated.

  In this embodiment, as shown in FIG. 14A, the wavelength conversion element 8 is disposed to face the resonator mirror 5 with the laser crystal 4 interposed therebetween.

  In the present embodiment, the first resonator 6 is formed by an end surface S6 opposite to the laser crystal of the wavelength conversion element 8 and an end surface S4 opposite to the laser crystal 4 of the resonator mirror 5.

  In the case of the present embodiment, the laser crystal 4 is formed so that the end face S1 opposite to the resonator mirror 5 is substantially transmitted (low reflection) with respect to the pump light. Further, the wavelength conversion element 8 is formed such that the end surface S6 opposite to the laser crystal 4 side is substantially reflected (highly reflected) with respect to the pump light. The reflection and transmission characteristics with respect to laser light of each wavelength at each end face other than the above are the same as those of the fifth embodiment. For example, the reflectance with respect to laser light of each wavelength at each end face (S1 to S6) By applying an appropriate coating, the setting is made as shown in FIG.

  Even with such a configuration, the structure is simple, suitable for downsizing, and the adjustment work is simple, and pump light in a single longitudinal mode can be generated, and high-quality idler light is output. It is possible to provide a solid-state laser capable. Further, similarly to the third embodiment, it is possible to suppress the power consumption by driving the excitation light source 2 while suppressing the output of the excitation light.

In all the embodiments described above, the laser crystal 4 has the end surface opposite to the excitation light input side, that is, the end surface S2 in the first, third, and fourth embodiments. In the sixth embodiment, an appropriate coating (reflectance HR) may be applied to the end surface S1 so that the excitation light is substantially reflected (highly reflected). When the excitation light is substantially transmitted through the end surface of the laser crystal 4 opposite to the input side of the excitation light, the thickness of the laser crystal 4 is set equal to the optical path length necessary and sufficient to generate the pump light. However, when the excitation light is reflected by applying a highly reflective coating to the end face S1 or end face S2 as described above, for example, the excitation light passes between the end face S1 and the end face S2 of the laser crystal. The distance for one round trip may be equal to the optical path length necessary and sufficient for generating pump light. Accordingly, by coating as described above, it is possible to reduce the thickness of the laser crystal 4, to shorten the resonator length d ₁ of the first resonator 6, further reducing the size of the solid-state laser 1 Can do.

  In the third to sixth embodiments, the signal light is reflected by the end face S6 and resonates between the end face S5 and the end face S6 of the wavelength conversion element 8. However, the present invention is not limited to this. May pass through the end surface S6. Even in this case, high-quality idler light can be output to the outside based on pump light in a single longitudinal mode.

DESCRIPTION OF SYMBOLS 1 ... Solid laser 2 ... Excitation light source 4 ... Laser crystal 5 ... Resonator mirror 6 ... 1st resonator 7 ... 2nd resonator 8 ... Wavelength conversion element

Claims (10)

A first resonator that resonates the pump light with a laser crystal that generates pump light by excitation light , and a resonator mirror that is disposed opposite to the laser crystal ;
In said first resonator comprises a second resonator for resonating portion of the pump light is resonated in the first resonator between end faces of the resonator mirrors, and
A solid-state laser in which the arrangement positions of the laser crystal and the resonator mirror are adjusted so that the gain peak frequency of the first resonator matches the gain peak frequency of the second resonator . The laser crystal is disposed between the light source of the excitation light and the resonator mirror, and substantially transmits the excitation light and substantially reflects the pump light through the end surface opposite to the resonator mirror. And forming the end face on the resonator mirror side so as to substantially transmit the pump light,
The resonator mirror has an end face opposite to the laser crystal formed so as to substantially reflect the pump light, and the end face on the laser crystal side is reflected by an end face opposite to the laser crystal. 2. The solid laser according to claim 1, wherein a part of the pump light is reflected. The laser crystal is disposed to face the light source of the excitation light with the resonator mirror interposed therebetween, and the end surface on the resonator mirror side is formed so as to substantially transmit the excitation light and the pump light, An end surface opposite to the resonator mirror is formed so as to substantially reflect the pump light,
The resonator mirror is formed such that an end surface opposite to the laser crystal is substantially transmitted with respect to the excitation light and substantially reflected with respect to the pump light, and an end surface on the laser crystal side is formed with the excitation light. The solid laser according to claim 1, wherein a part of the pump light which is substantially transmitted and is reflected by the end surface opposite to the laser crystal is reflected.   A wavelength conversion element that is disposed between the laser crystal and the resonator mirror and converts pump light having an output intensity equal to or greater than a predetermined threshold into signal light and idler light having different wavelengths from the pump light; The end face of the resonator mirror on the laser crystal side and the end face on the opposite side of the resonator mirror from the laser crystal are formed so as to substantially transmit the idler light, and the idler light is output to the outside. The solid-state laser according to claim 2.   A wavelength conversion element that is disposed opposite to the laser crystal with the resonator mirror interposed therebetween and converts pump light having an output intensity equal to or greater than a predetermined threshold into signal light and idler light having a wavelength different from that of the pump light. The solid-state laser according to claim 2, wherein the idler light is output to the outside.   A wavelength conversion element that is disposed opposite to the resonator mirror with the laser crystal interposed therebetween and converts pump light having an output intensity equal to or higher than a predetermined threshold into signal light and idler light having a wavelength different from that of the pump light. The solid-state laser according to claim 3, wherein the idler light is output to the outside. In a solid-state laser that generates pump light based on excitation light , amplifies it with a resonator, and outputs laser light having a wavelength different from that of the excitation light,
A laser crystal that generates the pump light by the input of the excitation light; and
A resonator mirror disposed between the light source of the excitation light and the laser crystal, and reflecting pump light generated by the laser crystal at an end surface opposite to the laser crystal;
Disposed facing apart from the resonator mirror across the laser crystal, the pumping light output intensity is above a predetermined threshold value, the said pump light is converted into a different signal light and the idler light wavelength, to the outside A wavelength conversion element that outputs the idler light;
With
Forming a first resonator for resonating the pump light generated from the laser crystal with an end surface of the wavelength conversion element opposite to the laser crystal and an end surface of the resonator mirror opposite to the laser crystal;
A second resonator for resonating a part of the pump light resonated by the first resonator is formed on an end surface of the resonator mirror opposite to the laser crystal and an end surface of the resonator mirror on the laser crystal side. Forming,
A configuration to match with the wavelength converting element and the resonator arrangement position of the mirror adjustment to the second resonator Geinpi over clock frequency of the first resonator gain peak frequency, output from the second cavity, A solid-state laser characterized in that the idler light is output from the wavelength conversion element to the outside based on pump light in a single longitudinal mode whose output intensity is a predetermined threshold value or more. 8. The solid-state laser according to claim 4 , wherein the wavelength conversion element causes the signal light to resonate between an end surface on the laser crystal side and an end surface opposite to the laser crystal side. .   9. The solid according to claim 1, wherein the laser crystal has an end surface opposite to an input side of the excitation light so as to substantially reflect the excitation light. laser.   10. The resonator mirror according to claim 1, wherein an end face on the laser crystal side has a planar shape, and an end face on the opposite side to the laser crystal has a convex shape. Solid laser.

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