Laser medium unit and laser device

Abstract

To provide a laser medium unit and a laser device capable of sufficiently suppressing both deterioration in laser medium characteristics due to stress birefringence and deterioration in laser medium characteristics due to thermal birefringence, and facilitating temperature control of the laser medium.SOLUTION: A laser medium unit 10A includes a laser medium 11 and a holder 12. The laser medium 11 has a pair of end faces 11a and 11b. The holder 12 surrounds the laser medium 11 and holds the laser medium 11 when viewed in a Z-axis direction. The holder 12 includes a deformation-allowing portion 131 extending from the inside to the outside of the holder 12 when viewed in the Z-axis direction. The laser medium 11 and the holder 12 are in contact with each other. A contact region R of the holder 12 with the laser medium 11 has a width in the Z-axis direction and extends along a side surface 11c of the laser medium 11 when viewed from the Z-axis direction.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a laser medium unit and a laser device.

Background Art

[0002] Patent Document 1 describes a laser medium unit including a disk-shaped laser medium, a holding plate that surrounds the laser medium when viewed in the thickness direction of the laser medium, and a C-ring, a spring, or a plurality of contact fingers (hereinafter referred to as "C-ring etc.") disposed between the laser medium and the holding plate. In the laser medium unit described in Patent Document 1, when the holding plate is cooled by a cooling gas, the C-ring etc. functions as a heat conduction part that releases the heat generated in the laser medium to the holding plate, and also functions as a stress relaxation part that relaxes the stress generated in the laser medium due to the shrinkage of the holding plate.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the laser medium unit described in Patent Document 1, it is assumed that the C-ring etc. functions as a stress relaxation part, and the deterioration of the characteristics of the laser medium due to stress birefringence is suppressed. However, in the laser medium unit described in Patent Document 1, since the contact between the C-ring etc. and the laser medium is insufficient, the C-ring etc. does not function sufficiently as a heat conduction part, and in addition to the fact that the deterioration of the characteristics of the laser medium due to thermal birefringence is not sufficiently suppressed, it is assumed that the temperature control of the laser medium becomes difficult.

[0005] Therefore, an object of the present invention is to provide a laser medium unit and a laser device that can sufficiently suppress both a decrease in the characteristics of a laser medium due to stress birefringence and a decrease in the characteristics of a laser medium due to thermal birefringence, and can easily control the temperature of the laser medium.

Means for Solving the Problems

[0006] The laser medium unit of the present invention includes a laser medium having a pair of end faces, and a holder that surrounds the laser medium and holds the laser medium when viewed from a direction intersecting the pair of end faces. The holder includes a deformation allowance portion that extends from the inside to the outside of the holder when viewed from a direction intersecting the pair of end faces. The laser medium and the holder are in contact with each other. The contact region between the holder and the laser medium has a width in a direction intersecting the pair of end faces, and extends along the outer edge of the laser medium when viewed from a direction intersecting the pair of end faces.

[0007] In this laser medium unit, the holder that holds the laser medium includes a deformation allowance portion that extends from the inside to the outside of the holder. Thereby, even if the laser medium unit is cooled and the holder contracts, the stress generated in the laser medium due to the contraction of the holder can be relaxed, and a decrease in the characteristics of the laser medium due to stress birefringence can be suppressed. Further, the contact region between the holder and the laser medium has a width in a direction intersecting the pair of end faces of the laser medium, and extends along the outer edge of the laser medium when viewed from this direction. Thereby, the heat generated in the laser medium can be efficiently released to the holder, a decrease in the characteristics of the laser medium due to thermal birefringence can be suppressed, and the temperature control of the laser medium can be facilitated. As described above, according to this laser medium unit, both a decrease in the characteristics of the laser medium due to stress birefringence and a decrease in the characteristics of the laser medium due to thermal birefringence can be sufficiently suppressed, and the temperature control of the laser medium can be easily performed.

[0008] In the laser medium unit of the present invention, the laser medium may have a plate shape with each of a pair of end faces as a main face. When the laser medium has a plate shape, for example, compared with the case where the laser medium has a rod shape, it may be difficult to secure the contact area with the laser medium in the holder. Therefore, when the laser medium has a plate shape, the configuration of the holder described above is particularly effective.

[0009] In the laser medium unit of the present invention, the holder may have a main body portion including a deformation allowance portion and a stress relaxation portion provided between the laser medium and the main body portion. Thereby, the stress generated in the laser medium due to the shrinkage of the holder can be more reliably relaxed, and the deterioration of the characteristics of the laser medium due to stress birefringence can be more reliably suppressed.

[0010] In the laser medium unit of the present invention, the laser medium may have an optical amplification region and an optical absorption region surrounding the optical amplification region when viewed from a direction intersecting a pair of end faces. Thereby, since a part of the emitted light generated in the optical amplification region is absorbed by the optical absorption region, the occurrence of parasitic oscillation is suppressed. Further, in the optical absorption region, heat is generated by the absorption of a part of the emitted light, so the configuration of the holder described above is particularly effective.

[0011] In the laser medium unit of the present invention, the deformation allowance portion may include a slit extending from the inside to the outside of the holder when viewed from a direction intersecting a pair of end faces. Thereby, it is possible to easily and surely obtain a holder that can achieve both relaxation of the stress generated in the laser medium due to the shrinkage of the holder and efficient escape of the heat generated in the laser medium to the holder.

[0012] In the laser medium unit of the present invention, the slit is each of a plurality of slits, and the plurality of slits may be arranged at equal angular intervals when viewed from a direction intersecting a pair of end faces. Thereby, the stress generated in the laser medium due to the shrinkage of the holder can be uniformly relaxed, and the heat generated in the laser medium can be uniformly released to the holder.

[0013] The laser medium unit of the present invention further includes a first elastic member, the slit is each of a plurality of slits, and the first elastic member may be disposed in each of the plurality of slits. Thereby, even if the holder is divided by the plurality of slits, the holder can be appropriately brought into contact with the laser medium.

[0014] The laser medium unit of the present invention further includes a mounting member, the slit is each of a plurality of slits, and the mounting member may surround the holder when viewed from a direction intersecting a pair of end faces. Thereby, even if the holder is divided by the plurality of slits, the holder can be appropriately brought into contact with the laser medium.

[0015] The laser medium unit of the present invention may further include a second elastic member disposed between the holder and the mounting member. Thereby, even if the holder is divided by the plurality of slits, the holder can be appropriately brought into contact with the laser medium.

[0016] In the laser medium unit of the present invention, the coefficient of thermal expansion of the mounting member may be smaller than that of the holder. Thereby, when the laser medium unit is cooled, the amount of shrinkage of the mounting member becomes smaller than the amount of shrinkage of the holder. However, since the second elastic member is disposed between the holder and the mounting member, it is possible to suppress the influence of the shrinkage of the mounting member on the laser medium.

[0017] In the laser medium unit of the present invention, the coefficient of thermal expansion of the mounting member may be larger than that of the holder. Thereby, when the laser medium unit is cooled, the amount of shrinkage of the mounting member becomes larger than the amount of shrinkage of the holder. However, since the second elastic member is disposed between the holder and the mounting member, it is possible to suppress the influence of the shrinkage of the mounting member on the laser medium.

[0018] The laser device of the present invention includes the above-described laser medium unit.

[0019] According to the laser device of the present invention, as described above, it is possible to sufficiently suppress both the deterioration of the characteristics of the laser medium due to stress birefringence and the deterioration of the characteristics of the laser medium due to thermal birefringence, and to facilitate the temperature control of the laser medium.

[0020] The laser device of the present invention may further include a chamber through which a refrigerant flows, accommodating a laser medium unit. Thereby, the laser medium unit can be efficiently cooled.

[0021] In the laser device of the present invention, the laser medium unit is each of a plurality of laser medium units, and each of the plurality of laser medium units may be arranged with a gap through which a refrigerant flows. Thereby, the plurality of laser medium units can be efficiently cooled.

[0022] The laser device of the present invention may further include a laser light source that emits laser light amplified by the laser medium unit, and an excitation light source that emits excitation light for exciting the laser medium. Thereby, laser light can be amplified with good characteristics.

[0023] In the laser device of the present invention, the excitation light source is each of a first excitation light source and a second excitation light source. The first excitation light source is arranged on one side in a direction intersecting a pair of end faces with respect to the laser medium unit, and the second excitation light source may be arranged on the other side in a direction intersecting a pair of end faces with respect to the laser medium unit. Thereby, laser light can be amplified with better characteristics.

Effects of the Invention

[0024] According to the present invention, it is possible to provide a laser medium unit and a laser device that can sufficiently suppress both the deterioration of the characteristics of the laser medium due to stress birefringence and the deterioration of the characteristics of the laser medium due to thermal birefringence, and can facilitate the temperature control of the laser medium.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Modes for Carrying Out the Invention

[0026] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same or corresponding parts are denoted by the same reference numerals, and redundant descriptions are omitted.

[0027] [First Embodiment] As shown in FIG. 1, the laser device 1 of the first embodiment includes a plurality of laser medium units 10A, a chamber 2, a laser light source 3, and a plurality of excitation light sources 4. Each laser medium unit 10A is arranged with a gap along the Z-axis direction.

[0028] The chamber 2 has a main body portion 21, a pair of window portions 22, an introduction portion 25, and a derivation portion 26. The main body portion 21 has an internal space S for accommodating a plurality of laser medium units 10A. A pair of openings 21a and a pair of openings 21b are formed in the main body portion 21. The pair of openings 21a face each other in the Z-axis direction. The pair of openings 21b face each other in the Y-axis direction.

[0029] Each window portion 22 is attached to the main body portion 21 so as to close each opening 21a. The window portion 22 includes a frame body 23 and a window member 24 held by the frame body 23. The window member 24 transmits the laser light L1 and the excitation light L2, which will be described later.

[0030] The introduction portion 25 has an introduction passage 25a. The introduction portion 25 is attached to the main body portion 21 such that the introduction passage 25a communicates with the internal space S through the opening 21b. The introduction portion 25 introduces a refrigerant C (for example, a cooling gas such as cryogenic helium gas) into the internal space S. The refrigerant C flows through a gap formed between adjacent laser medium units 10A in the internal space S. The discharge portion 26 has a discharge passage 26a. The discharge portion 26 is attached to the main body portion 21 such that the discharge passage 26a communicates with the internal space S through the opening 21b. The discharge portion 26 discharges the refrigerant C from the internal space S.

[0031] The laser light source 3 is disposed on one side in the Z-axis direction with respect to the chamber 2 (a plurality of laser medium units 10A). The laser light source 3 emits laser light L1, which is seed light, toward the plurality of laser medium units 10A. The laser light L1 emitted from the laser light source 3 enters the plurality of laser medium units 10A through the window member 24 of the window portion 22 disposed on one side in the Z-axis direction with respect to the plurality of laser medium units 10A. The laser light L1 is amplified by each laser medium unit 10A.

[0032] The plurality of excitation light sources 4 includes a pair of first excitation light sources 41 and a pair of second excitation light sources 42. The pair of first excitation light sources 41 is arranged on one side in the Z-axis direction with respect to the chamber 2 (the plurality of laser medium units 10A). Each first excitation light source 41 emits excitation light L2 to the plurality of laser medium units 10A. The excitation light L2 emitted from each first excitation light source 41 enters the plurality of laser medium units 10A through the window member 24 of the window portion 22 arranged on one side in the Z-axis direction with respect to the plurality of laser medium units 10A. The pair of second excitation light sources 42 is arranged on the other side in the Z-axis direction with respect to the chamber 2 (the plurality of laser medium units 10A). Each second excitation light source 42 emits excitation light L2 to the plurality of laser medium units 10A. The excitation light L2 emitted from each second excitation light source 42 enters the plurality of laser medium units 10A through the window member 24 of the window portion 22 arranged on the other side in the Z-axis direction with respect to the plurality of laser medium units 10A. The excitation light L2 excites the laser medium 11 described later.

[0033] As shown in FIGS. 2 and 3, the laser medium unit 10A includes a laser medium 11, a holder 12, and a first elastic member 15. The laser medium 11 has a pair of end faces 11a, 11b and a side face 11c. The laser medium 11 has a plate shape with a pair of end faces 11a, 11b as main faces. The laser medium 11 has, for example, a disk shape. The side face 11c of the laser medium 11 has a predetermined width in the Z-axis direction (the direction intersecting the pair of end faces 11a, 11b of the laser medium 11). The thickness of the laser medium 11 (that is, the width of the side face 11c in the Z-axis direction) is, for example, about several mm to several tens of mm.

[0034] The laser medium 11 is a solid laser medium. The laser medium 11 is, for example, YAG doped with Yb as an active element. The laser medium 11 is excited by the excitation light L2 and outputs emission light. The emission light is, for example, stimulated emission light. The stimulated emission light contributes to the optical amplification of the laser light L1.

[0035] The holding body 12 surrounds the laser medium 11 when viewed from the Z-axis direction and holds the laser medium 11. The holding body 12 has a main body portion 13 and a plurality of locking portions (claw portions) 14. The main body portion 13 has, for example, a plate shape. The main body portion 13 has an inner surface 13a and an outer surface 13b. In the first embodiment, the inner surface 13a of the main body portion 13 constitutes the inner surface 12a of the holding body 12, and the outer surface 13b of the main body portion 13 constitutes the outer surface 12b of the holding body 12.

[0036] The inner surface 13a extends along the side surface 11c of the laser medium 11 when viewed from the Z-axis direction. In the first embodiment, the inner surface 13a has a circular shape when viewed from the Z-axis direction. The outer surface 13b has, for example, a rectangular shape when viewed from the Z-axis direction. Each of the inner surface 13a and the outer surface 13b of the main body portion 13 has a predetermined width in the Z-axis direction (the thickness direction of the main body portion 13). The thickness of the main body portion 13 (that is, the width of each of the inner surface 13a and the outer surface 13b in the Z-axis direction) is, for example, about several mm to several tens of mm. The thickness of the main body portion 13 is substantially the same as the thickness of the laser medium 11. The coefficient of thermal expansion of the main body portion 13 is larger than that of the laser medium 11. The material of the main body portion 13 is, for example, copper or the like.

[0037] A pair of locking portions 14 are provided on one main surface of the main body portion 13. Similarly, a pair of locking portions 14 are provided on the other main surface of the main body portion 13. On each of the one main surface and the other main surface of the main body portion 13, the pair of locking portions 14 face each other through the inner region of the main body portion 13 when viewed from the Z-axis direction. On each of the one main surface and the other main surface of the main body portion 13, each locking portion 14 protrudes inside the main body portion 13 more than the inner surface 13a when viewed from the Z-axis direction.

[0038] The main body portion 13 surrounds the laser medium 11 when viewed from the Z-axis direction. That is, the laser medium 11 is disposed inside the main body portion 13. When viewed from the Z-axis direction, the diameter of the laser medium 11 is substantially the same as the diameter of the inner surface 13a of the main body portion 13. The movement of the laser medium 11 in a direction perpendicular to the Z-axis direction is restricted by the main body portion 13. The laser medium 11 is sandwiched by a plurality of locking portions 14 in the Z-axis direction. The movement of the laser medium 11 in the Z-axis direction is restricted by the plurality of locking portions 14. Thus, the laser medium 11 is held inside the main body portion 13 by the main body portion 13 and the plurality of locking portions 14.

[0039] The laser medium 11 and the holder 12 are in contact with each other. The laser medium 11 and the holder 12 are in direct contact without intervening other members (such as members with poor heat conductivity, etc.). Specifically, the side surface 11c of the laser medium 11 and the inner surface 13a of the main body portion 13 are in contact with each other. The contact region R between the laser medium 11 and the holder 12 has a predetermined width in the Z-axis direction. The width of the contact region R in the Z-axis direction is preferably 50% or more of the thickness of the laser medium 11, more preferably 70% or more of the thickness of the laser medium 11, and still more preferably 90% or more of the thickness of the laser medium 11. In the first embodiment, the inner surface 13a of the main body portion 13 corresponds to the contact region R. That is, the width of the contact region R in the Z-axis direction is substantially the same as the thickness of the laser medium 11.

[0040] The contact region R extends along the side surface 11c of the laser medium 11 when viewed from the Z-axis direction. That is, the contact region R extends along the outer edge of the laser medium 11 when viewed from the Z-axis direction. The contact region R does not depart from the outer edge of the laser medium 11 when viewed from the Z-axis direction. The side surface 11c of the laser medium 11 and the contact region R are a continuous surface. No recesses such as holes are formed in the side surface 11c and the contact region R. There is no space between the side surface 11c and the contact region R. The laser medium 11 and the holder 12 are in continuous and gapless contact in the contact region R. The laser medium 11 and the holder 12 are in close contact with each other in the contact region R.

[0041] The main body portion 13 includes a plurality of deformation allowance portions 131 that allow deformation of the main body portion 13. Each deformation allowance portion 131 extends from the inside to the outside of the holder 12 when viewed from the Z-axis direction. Each deformation allowance portion 131 is a slit 13c. Each slit 13c extends from the inside to the outside of the holder 12 when viewed from the Z-axis direction. Each slit 13c reaches the inner surface 13a and the outer surface 13b of the main body portion 13. As a result, the main body portion 13 is divided into a plurality of main body members 132. The plurality of slits 13c are arranged at equal angular intervals when viewed from the Z-axis direction. As an example, each slit 13c extends from a position approximately at the center of each side portion of the outer surface 13b of the main body portion 13 toward the inner surface 13a when viewed from the Z-axis direction.

[0042] When viewed from the Z-axis direction, the width of each slit 13c is sufficiently small with respect to the length of the inner surface 13a (side surface 11c of the laser medium 11) of the main body portion 13. When viewed from the Z-axis direction, the width of each slit 13c is 5% or less of the length of the inner surface 13a (side surface 11c of the laser medium 11) of the main body portion 13. The width of the slit 13c when viewed from the Z-axis direction is smaller than the length of the slit 13c in the extending direction of the slit 13c. The width of the slit 13c when viewed from the Z-axis direction is smaller than the width of the contact region R in the Z-axis direction. The width of the slit 13c when viewed from the Z-axis direction is, for example, on the order of several hundred μm to several mm.

[0043] The first elastic member 15 is disposed in each slit 13c. The first elastic member 15 is constituted by, for example, a plurality of wire-shaped elastic bodies overlapping each other. The material of the first elastic member 15 is, for example, copper or the like. The first elastic member 15 is, for example, a copper mesh. The first elastic member 15 is fixed to the side surfaces of the respective main body members 132 constituting the slit 13c by, for example, welding or brazing. The plurality of main body members 132 are integrally held by the first elastic member 15. The inner surface 13a of the main body portion 13 is in contact with the side surface 11c of the laser medium 11 by the elastic force of the first elastic member 15. Specifically, in a state where the inner surface 13a of the main body portion 13 is in contact with the side surface 11c of the laser medium 11, the first elastic member 15 is being pulled. The plurality of main body members 132 are brought closer to each other by the elastic force of the first elastic member 15.

[0044] As described above, in the laser medium unit 10A, the holder 12 that holds the laser medium 11 includes a deformation allowance portion 131 that extends from the inside to the outside of the holder 12. Thereby, even if the laser medium unit 10A is cooled and the holder 12 contracts, the stress generated in the laser medium 11 due to the contraction of the holder 12 can be relaxed, and the deterioration of the characteristics of the laser medium 11 caused by stress birefringence can be suppressed. Further, the contact region R of the holder 12 with the laser medium 11 has a width in the Z-axis direction and extends along the side surface 11c of the laser medium 11 when viewed from the Z-axis direction. That is, there is no space between the contact region R of the holder 12 and the side surface 11c of the laser medium 11. The holder 12 and the laser medium 11 are in close contact with each other in the contact region R. Further, when viewed from the Z-axis direction, the width of each slit 13c is sufficiently small with respect to the length of the inner surface 13a of the main body portion 13. Thereby, the heat generated in the laser medium 11 can be efficiently released to the holder 12, the deterioration of the characteristics of the laser medium 11 caused by thermal birefringence can be suppressed, and the temperature control of the laser medium 11 can be facilitated. Since the laser medium 11 may have a property of easily accumulating heat, it is particularly important to efficiently cool the laser medium 11. According to the above configuration, the heat of the laser medium 11 can be efficiently released, and the deterioration or destabilization of the characteristics of the laser medium 11 can be suppressed. As described above, according to the laser medium unit 10A, both the deterioration of the characteristics of the laser medium 11 caused by stress birefringence and the deterioration of the characteristics of the laser medium 11 caused by thermal birefringence can be sufficiently suppressed, and the temperature control of the laser medium 11 can be facilitated.

[0045] In the laser medium unit 10A, the laser medium 11 has a plate shape with each of a pair of end faces 11a and 11b as a main surface. When the laser medium 11 has a plate shape, for example, compared with the case where the laser medium has a rod shape, there is a possibility that it becomes difficult to secure the contact region R with the laser medium 11 in the holder 12. Therefore, when the laser medium 11 has a plate shape, the configuration of the holder 12 described above is particularly effective. In addition to the contact region R with the laser medium 11 in the holder 12, heat generated in the laser medium 11 can be efficiently released from the pair of end faces 11a and 11b of the laser medium 11 as well.

[0046] In the laser medium unit 10A, the deformation allowance portion 131 includes a slit 13c that extends from the inside to the outside of the holder 12 when viewed in the Z-axis direction. Thereby, it is possible to easily and surely obtain a holder that can achieve both relaxing the stress generated in the laser medium 11 due to the shrinkage of the holder 12 and efficiently releasing the heat generated in the laser medium 11 to the holder.

[0047] In the laser medium unit 10A, the plurality of slits 13c are arranged at equal angular intervals when viewed in the Z-axis direction. Thereby, the stress generated in the laser medium 11 due to the shrinkage of the holder 12 can be uniformly relaxed, and the heat generated in the laser medium 11 can be uniformly released to the holder 12.

[0048] The laser medium unit 10A includes a first elastic member 15. The first elastic member 15 is disposed in each of the plurality of slits 13c. Thereby, even if the holder 12 is divided by the plurality of slits 13c, the holder 12 can be appropriately brought into contact with the laser medium 11.

[0049] According to the laser device 1, as described above, it is possible to sufficiently suppress both the degradation of the characteristics of the laser medium 11 due to stress birefringence and the degradation of the characteristics of the laser medium 11 due to thermal birefringence, and to facilitate the temperature control of the laser medium 11.

[0050] The laser device 1 includes a chamber 2 in which a laser medium unit 10A is accommodated and through which a refrigerant C flows. Thereby, the laser medium unit 10A can be efficiently cooled.

[0051] In the laser device 1, each of the plurality of laser medium units 10A is arranged with a gap through which the refrigerant C flows therebetween. Thereby, the plurality of laser medium units 10A can be efficiently cooled.

[0052] The laser device 1 includes a laser light source 3 that emits laser light L1 amplified by the laser medium unit 10A, and an excitation light source 4 that emits excitation light L2 for exciting the laser medium 11. Thereby, the laser light L1 can be amplified with good characteristics.

[0053] In the laser device 1, a first excitation light source 41 is arranged on one side in the Z-axis direction with respect to the laser medium unit 10A, and a second excitation light source 42 is arranged on the other side in the Z-axis direction with respect to the laser medium unit 10A. Thereby, the laser light L1 can be amplified with better characteristics.

[0054] [Second Embodiment] As shown in FIGS. 4 and 5, the laser medium unit 10B of the second embodiment mainly differs from the laser medium unit 10A of the first embodiment in that it includes a holding body 12B instead of the holding body 12, further includes a mounting member 16, and does not include a first elastic member 15.

[0055] The laser medium unit 10B includes a holding body 12B. The holding body 12B has a pair of main body portions 13A and 13B. The main body portion 13A corresponds to a part of one side in the Z-axis direction of the main body portion 13 of the first embodiment, and the main body portion 13B corresponds to a part of the other side in the Z-axis direction of the main body portion 13 of the first embodiment.

[0056] Specifically, each main body portion 13A, 13B has an inner surface 13a and an outer surface 13b. The thickness of each main body portion 13A, 13B is about half of the thickness of the main body portion 13 in the first embodiment. A pair of locking portions 14 are provided on one main surface of the main body portion 13A. A pair of locking portions 14 are provided on the other main surface of the main body portion 13B. The laser medium 11 is sandwiched between the main body portion 13A and the main body portion 13B in the Z-axis direction. Each main body portion 13A, 13B includes a plurality of deformation allowance portions 131. Each deformation allowance portion 131 is a slit 13c. In a state where the laser medium 11 is sandwiched between the main body portion 13A and the main body portion 13B, the main body portions 13A, 13B have the same configuration as the main body portion 13 in the first embodiment. In the second embodiment, the first elastic member 15 is not disposed in each slit 13c.

[0057] The laser medium unit 10B includes a mounting member 16. The mounting member 16 surrounds the holder 12B when viewed from the Z-axis direction. Specifically, the mounting member 16 has a first mounting member 161 and a second mounting member 162. The first mounting member 161 has, for example, a rectangular frame shape. A first step portion 16c and a second step portion 16d are formed between the inner edge 16a and the outer edge 16b of the first mounting member 161. The first step portion 16c has, for example, a rectangular shape when viewed from the Z-axis direction. The second step portion 16d is located outside the first step portion 16c when viewed from the Z-axis direction. The second step portion 16d extends along the Y-axis direction and reaches the outer edge 16b of the first mounting member 161 when viewed from the Z-axis direction.

[0058] The second mounting member 162 has, for example, a rectangular frame shape. The inner edge 16e of the second mounting member 162 substantially coincides with the inner edge 16a of the first mounting member 161 when viewed from the Z-axis direction. The outer edge 16f of the second mounting member 162 substantially coincides with the second step portion 16d of the first mounting member 161 when viewed from the Z-axis direction. The second mounting member 162 is disposed on the second step portion 16d of the first mounting member 161.

[0059] The outer surfaces 13b of the pair of main body parts 13A and 13B are located outside the inner edge 16a of the first attachment member 161 and the inner edge 16e of the second attachment member 162 when viewed from the Z-axis direction, and substantially coincide with the first step portion 16c. The laser medium 11 and the holder 12B are sandwiched between the first attachment member 161 and the second attachment member 162 in a state of being disposed on the first step portion 16c. Thus, the holder 12B is collectively held by the attachment member 16.

[0060] As described above, the laser medium unit 10B includes the attachment member 16. The attachment member 16 surrounds the holder 12B when viewed from the Z-axis direction. Thereby, even if the holder 12 is divided by the plurality of slits 13c, the holder 12 can be appropriately brought into contact with the laser medium 11.

[0061] [Third Embodiment] As shown in FIG. 6, the laser medium unit 10C of the third embodiment mainly differs from the laser medium unit 10A of the first embodiment in that it includes a laser medium 11C instead of the laser medium 11, includes a holder 12C instead of the holder 12, does not include the first elastic member 15, further includes an attachment member 18, and further includes a second elastic member 19.

[0062] The laser medium unit 10C includes a laser medium 11C. The laser medium 11C has an optical amplification region 111 and an optical absorption region 112. The optical amplification region 111 is, for example, YAG doped with Yb as an active element. The optical amplification region 111 has, for example, a disk shape. The optical absorption region 112 surrounds the optical amplification region 111 when viewed from the Z-axis direction. The optical absorption region 112 is integrally formed with the optical amplification region 111. The optical absorption region 112 suppresses the occurrence of parasitic oscillation by absorbing a part of the emission light generated in the optical amplification region 111. The outer surface of the optical absorption region 112 constitutes the side surface 11c of the laser medium 11C. The material of the optical absorption region 112 is, for example, Cr:YAG ceramics, Sm:YAG, black ink, or black resin.

[0063] The laser medium unit 10C includes a holder 12C. The holder 12C has a main body portion 13 and a stress relaxation portion 17. The stress relaxation portion 17 is provided on the inner surface 13a of the main body portion 13. That is, the stress relaxation portion 17 is provided between the laser medium 11C and the main body portion 13. The stress relaxation portion 17 has a ring shape. The stress relaxation portion 17 has a predetermined width in the Z-axis direction. The width of the stress relaxation portion 17 in the Z-axis direction is, for example, about several mm to several tens of mm. The width of the stress relaxation portion 17 in the Z-axis direction is substantially the same as the thickness of the laser medium 11C. The stress relaxation portion 17 extends along the side surface 11c of the laser medium 11C when viewed from the Z-axis direction. The stress relaxation portion 17 is continuously connected when viewed from the Z-axis direction. For example, a notch or the like may be locally formed in the stress relaxation portion 17. The notch may be formed at a position corresponding to the slit 13c of the main body portion 13 and may have substantially the same width as the slit 13c.

[0064] The laser medium 11C and the holder 12C are in contact with each other. Specifically, the side surface 11c of the laser medium 11C and the inner surface 17a of the stress relaxation portion 17 are in contact with each other. In the third embodiment, the inner surface 17a of the stress relaxation portion 17 constitutes the inner surface 12a of the holder 12. In the third embodiment, the inner surface 17a of the stress relaxation portion 17 corresponds to the contact region R. The elastic modulus of the stress relaxation portion 17 is smaller than the elastic modulus of the main body portion 13. The thermal conductivity of the stress relaxation portion 17 is larger than the thermal conductivity of the laser medium 11C. The absolute value of the difference between the thermal conductivity of the stress relaxation portion 17 and the thermal conductivity of the main body portion 13 is smaller than the absolute value of the difference between the thermal conductivity of the stress relaxation portion 17 and the thermal conductivity of the laser medium 11C. That is, the thermal conductivity of the stress relaxation portion 17 is closer to that of the main body portion 13 than that of the laser medium 11C. The material of the stress relaxation portion 17 is, for example, indium or the like.

[0065] The laser medium unit 10C includes a mounting member 18. The mounting member 18 surrounds the holder 12C when viewed from the Z-axis direction. The mounting member 18 has, for example, a rectangular frame shape when viewed from the Z-axis direction. The inner surface 18a of the mounting member 18 is located outside the outer surface 13b of the main body 13 when viewed from the Z-axis direction. The coefficient of thermal expansion of the mounting member 18 is smaller than that of the main body 13. The material of the mounting member 18 is, for example, stainless steel or the like.

[0066] The laser medium unit 10C includes a second elastic member 19. The second elastic member 19 is disposed between the main body 13 and the mounting member 18. The second elastic member 19 extends along the outer surface 13b of the main body 13 when viewed from the Z-axis direction. Similar to the first elastic member 15, the second elastic member 19 is composed of, for example, a plurality of overlapping wire-shaped elastic bodies. The material of the second elastic member 19 is, for example, copper or the like. The second elastic member 19 is, for example, a copper mesh. The second elastic member 19 is fixed to the outer surface 13b of the main body 13 and the inner surface 18a of the mounting member 18 by, for example, welding or brazing.

[0067] The plurality of main body members 132 of the main body 13 are collectively held by the mounting member 18 and the second elastic member 19. The inner surface 17a of the stress relaxation portion 17 contacts the side surface 11c of the laser medium 11C by the elastic force of the second elastic member 19. Specifically, the second elastic member 19 is compressed. The plurality of main body members 132 are pressed against the laser medium 11C by the elastic force of the second elastic member 19. The inner surface 17a of the stress relaxation portion 17 contacts the side surface 11c of the laser medium 11C by being pressed by the plurality of main body members 132. In addition, in FIG. 6, the illustration of the locking portion 14 is omitted.

[0068] As described above, in the laser medium unit 10C, the holder 12C has a main body portion 13 including a deformation tolerance portion 131, and a stress relaxation portion 17 provided between the laser medium 11C and the main body portion 13. Thereby, the stress generated in the laser medium 11C due to the shrinkage of the holder 12C can be more reliably relaxed, and the deterioration of the characteristics of the laser medium 11C caused by stress birefringence can be more reliably suppressed. Further, since the elastic modulus of the stress relaxation portion 17 is smaller than the elastic modulus of the main body portion 13, the adhesion between the laser medium 11C and the holder 12C can be improved. Thereby, the heat generated in the laser medium 11C can be more efficiently dissipated to the holder 12C.

[0069] In the laser medium unit 10C, the laser medium 11C has an optical amplification region 111 and an optical absorption region 112 that surrounds the optical amplification region 111 when viewed from the Z-axis direction. Thereby, since a part of the emitted light generated in the optical amplification region 111 is absorbed by the optical absorption region 112, the occurrence of parasitic oscillation is suppressed. Further, in the optical absorption region 112, heat is generated by the absorption of a part of the emitted light, so the configuration of the holder 12C described above is particularly effective. Further, when the laser medium 11C has a plate shape, cooling from the end face, which is the main surface of the laser medium 11C (end face cooling), is mainstream (general), and cooling from the side surface 11c of the laser medium 11C (side surface cooling) tends not to be noticed. Furthermore, when the laser medium 11C has an optical absorption region 112 that suppresses parasitic oscillation, heat generation particularly increases at the side surface 11c of the laser medium 11C. Therefore, according to the configuration of the holder 12C described above, for example, end face cooling with a refrigerant such as a cooling gas and side surface cooling by the holder 12C are possible, the heat generated in the laser medium 11C can be efficiently dissipated, and the deterioration of the laser characteristics of the laser medium 11C can be effectively suppressed.

[0070] The laser medium unit 10C includes a second elastic member 19 disposed between the holder 12C and the attachment member 18. Thereby, even if the holder 12C is divided by a plurality of slits 13c, the holder 12C can be appropriately brought into contact with the laser medium 11C.

[0071] In the laser medium unit 10C, the coefficient of thermal expansion of the mounting member 18 is smaller than that of the main body portion 13. As a result, when the laser medium unit 10C is cooled, the amount of shrinkage of the mounting member 18 becomes smaller than the amount of shrinkage of the holder 12C. However, the difference between the amount of shrinkage of the mounting member 18 and the amount of shrinkage of the holder 12C can be adjusted by the second elastic member 19 disposed between the holder 12C and the mounting member 18, and the influence of the shrinkage of the mounting member 18 on the laser medium 11C can be suppressed.

[0072] [Modification Example] As described above, each embodiment of the present invention has been described, but the present invention is not limited to the above-described embodiments.

[0073] In the third embodiment, an example in which the outer surface 13b of the main body portion 13 has a rectangular shape when viewed from the Z-axis direction has been shown. However, as shown in FIG. 7, the main body portion 13D may have, for example, an annular shape when viewed from the Z-axis direction. In this case, the inner surface 18a of the mounting member 18D has a circular shape when viewed from the Z-axis direction. Further, the second elastic member 19 may not be disposed between the holder 12D and the mounting member 18D. In this case, the coefficient of thermal expansion of the mounting member 18D is larger than that of the main body portion 13D. As a result, when the mounting member 18D is cooled, the holder 12D can be held by the shrinkage of the mounting member 18D, and the holder 12D can be appropriately brought into contact with the laser medium 11C. Further, as shown in FIG. 8, the main body portion 13E may include one slit 13c (deformation allowance portion 131).

[0074] In the first embodiment, an example in which the first elastic member 15 is constituted by a plurality of wire-like elastic bodies overlapping each other has been shown. However, as shown in FIG. 9, the first elastic member 15 may be, for example, a spring or the like. Also in the third embodiment, the second elastic member 19 may be, for example, a spring or the like. Each of the first elastic member 15 and the second elastic member 19 may be constituted by an elastic resin such as an elastic adhesive.

[0075] In each embodiment, an example in which the laser media 11, 11C are plate-shaped has been shown. However, the laser media 11, 11C may be, for example, rod-shaped. Also, an example in which the laser media 11, 11C are disk-shaped has been shown. However, the laser media 11, 11C may be, for example, rectangular plate-shaped.

[0076] In each embodiment, an example in which the slit 13c reaches the inner surface 13a and the outer surface 13b of the main body portions 13, 13A, 13B has been shown. However, the slit 13c may not reach the inner surface 13a and the outer surface 13b of the main body portions 13, 13A, 13B. The slit 13c may reach either one of the inner surface 13a and the outer surface 13b of the main body portions 13, 13A, 13B, and may not reach either the inner surface 13a or the outer surface 13b. That is, the slit 13c may reach at least one of the inner surface 13a and the outer surface 13b of the main body portions 13, 13A, 13B.

[0077] In each embodiment, an example in which each deformation allowance portion 131 is the slit 13c has been shown. However, the deformation allowance portion 131 may not be the slit 13c. The deformation allowance portion 131 may be, for example, a first region of the holders 12, 12B, 12C, and a region having an elastic coefficient smaller than that of a second region of the holders 12, 12B, 12C. Also, the deformation allowance portion 131 may be, for example, a first region of the holders 12, 12B, 12C, and a region having a thickness in the Z-axis direction smaller than that of a second region of the holders 12, 12B, 12C. That is, the deformation allowance portion 131 may not penetrate the holders 12, 12B, 12C in the Z-axis direction. The deformation allowance portion 131 may be any portion that allows deformation of the holders 12, 12B, 12C.

[0078] Each of the laser medium unit 10A of the first embodiment and the laser medium unit 10B of the second embodiment may also include a holder 12C having a stress relaxation portion 17, similar to the laser medium unit 10C of the third embodiment.

[0079] Each of the laser medium unit 10A of the first embodiment and the laser medium unit 10B of the second embodiment may also include a laser medium 11C having an optical amplification region 111 and an optical absorption region 112, similar to the laser medium unit 10C of the third embodiment.

[0080] In the third embodiment, an example where the optical absorption region 112 is integrally formed with the optical amplification region 111 has been shown. However, the optical absorption region 112 may be formed separately from the optical amplification region 111. The optical absorption region 112 may be provided as a separate member on the side surface of the optical amplification region 111.

[0081] In the third embodiment, an example where the thermal expansion coefficient of the mounting member 18 is smaller than that of the main body portion 13 has been shown. However, the thermal expansion coefficient of the mounting member 18 may be larger than that of the main body portion 13. In this case, when the laser medium unit 10C is cooled, the amount of contraction of the mounting member 18 becomes larger than the amount of contraction of the holder 12C. However, the difference between the amount of contraction of the mounting member 18 and the amount of contraction of the holder 12C can be adjusted by the second elastic member 19 disposed between the holder 12C and the mounting member 18, and the influence of the contraction of the mounting member 18 on the laser medium 11C can be suppressed.

Description of Reference Numerals

[0082] 1... Laser device, 2... Chamber, 3... Laser light source, 4... Excitation light source, 10A, 10B, 10C... Laser medium unit, 11, 11C... Laser medium, 11a, 11b... End face, 11c... Side face, 12, 12B, 12C, 12D... Holder, 13, 13A, 13B, 13D... Main body portion, 13c... Slit, 15... First elastic member, 16, 18, 18D... Mounting member, 17... Stress relaxation portion, 19... Second elastic member, 41... First excitation light source, 42... Second excitation light source, 111... Optical amplification region, 112... Optical absorption region, 131... Deformation allowance portion, C... Refrigerant.

Claims

1. a laser medium having a pair of end faces; a holder that surrounds the laser medium and holds the laser medium when viewed from a direction intersecting the pair of end faces; the laser medium has a plate shape with each of the pair of end faces as a main face; the holder includes a deformation allowance portion that extends from the inside to the outside of the holder when viewed from the direction intersecting the pair of end faces; the laser medium and the holder are in contact with each other; the contact region of the holder with the laser medium has a width in the direction intersecting the pair of end faces and extends along the outer edge of the laser medium when viewed from the direction intersecting the pair of end faces; the holder has a main body portion including the deformation allowance portion and a stress relaxation portion provided between the laser medium and the main body portion; the deformation allowance portion is not formed as the same member as the stress relaxation portion, a laser medium unit.

2. the laser medium has an optical amplification region and an optical absorption region that surrounds the optical amplification region when viewed from the direction intersecting the pair of end faces, the laser medium unit according to claim 1.

3. the deformation allowance portion includes a slit that extends from the inside to the outside of the holder when viewed from the direction intersecting the pair of end faces, the laser medium unit according to claim 1 or 2.

4. each of the slits is one of a plurality of slits; the plurality of slits are arranged at equal angular intervals when viewed from the direction intersecting the pair of end faces, the laser medium unit according to claim 3.

5. further comprising a first elastic member; each of the slits is one of a plurality of slits; the first elastic member is disposed in each of the plurality of slits, the laser medium unit according to claim 3 or 4.

6. further comprising a mounting member; each of the slits is one of a plurality of slits; the mounting member surrounds the holder when viewed from the direction intersecting the pair of end faces, the laser medium unit according to any one of claims 3 to 5.

7. further comprising a second elastic member disposed between the holder and the mounting member, the laser medium unit according to claim 6.

8. the thermal expansion coefficient of the mounting member is smaller than that of the holder, the laser medium unit according to claim 7.

9. The laser medium unit according to claim 7, wherein the thermal expansion coefficient of the mounting member is larger than the thermal expansion coefficient of the holding body.

10. A laser device comprising the laser medium unit according to any one of claims 1 to 9.

11. The laser device according to claim 10, further comprising a chamber in which the laser medium unit is accommodated and through which a refrigerant flows.

12. The laser medium unit is each of a plurality of laser medium units, The laser device according to claim 11, wherein each of the plurality of laser medium units is arranged with a gap through which the refrigerant flows.

13. A laser light source that emits laser light amplified by the laser medium unit, The laser device according to any one of claims 10 to 12, further comprising an excitation light source that emits excitation light for exciting the laser medium.

14. The excitation light source is each of a first excitation light source and a second excitation light source, The first excitation light source is arranged on one side in the direction intersecting the pair of end faces with respect to the laser medium unit, The laser device according to claim 13, wherein the second excitation light source is arranged on the other side in the direction intersecting the pair of end faces with respect to the laser medium unit.

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