Laser medium unit and laser device

Abstract

The laser medium unit comprises a laser medium and a retainer. The laser medium has a pair of cross-sections. The retainer surrounds the laser medium and holds it when viewed from a direction intersecting the pair of cross-sections. The retainer includes a deformation-allowing portion that extends from the inner side to the outer side of the retainer when viewed from a direction intersecting the pair of cross-sections. The laser medium and the retainer are in contact with each other. The contact area with the laser medium in the retainer has a width in a direction intersecting the pair of cross-sections and extends along the side of the laser medium when viewed from a direction intersecting the pair of cross-sections.

Description

Technology Field

[0001] The present disclosure relates to a laser medium unit and a laser device. Background Technology

[0002] Patent Document 1 describes a laser medium unit comprising a laser medium having a disc shape, a retaining plate surrounding the laser medium when viewed from the thickness direction, and a C-ring, a spring, or a plurality of contact fingers (hereinafter referred to as "C-ring, etc."). The C-ring, etc. is disposed between the laser medium and the retaining plate. In the laser medium unit described in Patent Document 1, when the retaining plate is cooled by a cooling gas, the C-ring, etc. functions as a heat conduction part that dissipates heat generated from the laser medium to the retaining plate, and also functions as a stress relief part that relieves stress generated in the laser medium due to the contraction of the retaining plate. Prior art literature

[0003] Patent Document 1: International Publication No. 2013 / 093503 The problem to be solved

[0004] In the laser medium unit described in Patent Document 1, it is assumed that the C-ring, etc. functions as a stress relief part, and thereby suppresses the degradation of the laser medium's properties caused by stress birefringence. 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 sufficiently function as a heat conduction part, and thereby, in addition to not sufficiently suppressing the degradation of the laser medium's properties caused by thermal birefringence, it is assumed that temperature control of the laser medium becomes difficult.

[0005] Accordingly, the present disclosure aims to provide a laser medium unit and a laser device capable of sufficiently suppressing both the degradation of the laser medium properties caused by stress birefringence and the degradation of the laser medium properties caused by thermal birefringence, while also facilitating temperature control of the laser medium. means of solving the problem

[0006] A laser medium unit of one aspect of the present disclosure comprises a laser medium having a pair of end faces and a retainer that surrounds the laser medium when viewed from a direction intersecting the pair of end faces and holds the laser medium, wherein the retainer includes a deformation-allowing portion that extends from the inside to the outside of the retainer when viewed from a direction intersecting the pair of end faces, and the laser medium and the retainer are in contact with each other, and the contact area with the laser medium in the retainer 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, a retainer that holds the laser medium includes a deformation-allowing portion extending from the inner side to the outer side of the retainer. By doing so, even if the laser medium unit cools and the retainer contracts, the stress generated in the laser medium due to the contraction of the retainer can be relieved, thereby suppressing the degradation of the laser medium's properties caused by stress birefringence. Furthermore, the contact area between the retainer and the laser medium has a width in a direction intersecting a pair of cross-sections of the laser medium and extends along the outer edge of the laser medium when viewed from that direction. By doing so, heat generated from the laser medium can be efficiently dissipated to the retainer, thereby suppressing the degradation of the laser medium's properties caused by thermal birefringence and facilitating temperature control of the laser medium. According to the above, this laser medium unit can sufficiently suppress both the degradation of laser medium properties caused by stress birefringence and the degradation of laser medium properties caused by thermal birefringence, and also facilitate temperature control of the laser medium.

[0008] In a laser medium unit of one aspect of the present disclosure, the laser medium may have a plate shape with each of a pair of cross-sections as the main surface. When the laser medium has a plate shape, there is a concern that it may be difficult to secure a contact area with the laser medium in the retainer compared to, for example, when the laser medium has a rod shape. Therefore, when the laser medium has a plate shape, the configuration of the retainer described above is particularly effective.

[0009] In a laser medium unit of one aspect of the present disclosure, the retainer may have a main body portion including a deformation-allowing portion and a stress-relieving portion provided between the laser medium and the main body portion. By doing so, the stress generated in the laser medium due to the contraction of the retainer can be relieved more effectively, thereby more effectively suppressing the degradation of the laser medium properties caused by stress birefringence.

[0010] In a laser medium unit of one aspect of the present disclosure, the laser medium may have a light amplification region and a light absorption region surrounding the light amplification region when viewed from a direction intersecting a pair of cross-sections. By doing so, since a portion of the emitted light generated in the light amplification region is absorbed by the light absorption region, the occurrence of parasitic oscillation is suppressed. Furthermore, since heat is generated in the light absorption region due to the absorption of a portion of the emitted light, the configuration of the above-described retainer is particularly effective.

[0011] In a laser medium unit of one aspect of the present disclosure, the deformation-allowing portion may include a slit extending from the inner side to the outer side of the retainer when viewed from a direction intersecting a pair of cross-sections. By doing so, it is possible to easily and reliably obtain a retainer capable of both relieving stress generated in the laser medium due to the contraction of the retainer and efficiently dissipating heat generated in the laser medium into the retainer.

[0012] In a laser medium unit of one aspect of the present disclosure, the slits are each of a plurality of slits, and the plurality of slits may be arranged at equal intervals when viewed from a direction intersecting a pair of cross-sections. By doing so, the stress generated in the laser medium due to the contraction of the retainer can be uniformly relieved, and the heat generated in the laser medium can be uniformly dissipated to the retainer.

[0013] A laser medium unit of one aspect of the present disclosure further comprises a first elastic member, and the slits are each of a plurality of slits, and the first elastic member may be disposed in each of the plurality of slits. By this, even if a retainer is divided by a plurality of slits, the retainer can be properly brought into contact with the laser medium.

[0014] A laser medium unit of one aspect of the present disclosure further comprises a mounting member, and the slits are each of a plurality of slits, and the mounting member may surround a retainer when viewed from a direction intersecting a pair of cross-sections. By this, even if the retainer is divided by a plurality of slits, the retainer can be properly brought into contact with the laser medium.

[0015] A laser medium unit of one aspect of the present disclosure may further comprise a second elastic member disposed between a retainer and a mounting member. By doing so, even if the retainer is divided by a plurality of slits, the retainer can be properly brought into contact with the laser medium.

[0016] In a laser medium unit of one aspect of the present disclosure, the thermal expansion rate of the mounting member may be smaller than the thermal expansion rate of the retainer. By this, when the laser medium unit is cooled, the amount of shrinkage of the mounting member becomes smaller than the amount of shrinkage of the retainer, but since a second elastic member is disposed between the retainer and the mounting member, the effect of the shrinkage of the mounting member on the laser medium can be suppressed.

[0017] In a laser medium unit of one aspect of the present disclosure, the thermal expansion rate of the mounting member may be greater than the thermal expansion rate of the retainer. As a result, when the laser medium unit is cooled, the amount of shrinkage of the mounting member becomes greater than the amount of shrinkage of the retainer, but since a second elastic member is disposed between the retainer and the mounting member, the effect of the shrinkage of the mounting member on the laser medium can be suppressed.

[0018] A laser device of one aspect of the present disclosure comprises the laser medium unit.

[0019] According to a laser device of one aspect of the present disclosure, as described above, it is possible to sufficiently suppress both the degradation of the laser medium properties caused by stress birefringence and the degradation of the laser medium properties caused by thermal birefringence, and at the same time facilitate temperature control of the laser medium.

[0020] A laser device of one aspect of the present disclosure may further comprise a chamber through which a coolant flows, in addition to housing a laser medium unit. By doing so, the laser medium unit can be cooled efficiently.

[0021] In a laser device of one aspect of the present disclosure, 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 coolant flows. By doing so, the plurality of laser medium units can be cooled efficiently.

[0022] A laser device of one aspect of the present disclosure may further comprise a laser light source that emits laser light amplified by a laser medium unit, and an excitation light source that emits excitation light that excites a laser medium. By doing so, laser light can be amplified with good characteristics.

[0023] In a laser device of one aspect of the present disclosure, the excitation light source is each a first excitation light source and a second excitation light source, and the first excitation light source may be disposed on one side in a direction intersecting a pair of cross-sections with respect to the laser medium unit, and the second excitation light source may be disposed on the other side in a direction intersecting a pair of cross-sections with respect to the laser medium unit. By doing so, the laser light can be amplified with better characteristics. Effects of the invention

[0024] According to the present disclosure, it is possible to provide a laser medium unit and a laser device capable of sufficiently suppressing both the degradation of the laser medium properties caused by stress birefringence and the degradation of the laser medium properties caused by thermal birefringence, while also facilitating temperature control of the laser medium. Brief explanation of the drawing

[0025] FIG. 1 is a configuration diagram of a laser device of a first embodiment. Figure 2 is a front view of the laser medium unit shown in Figure 1. FIG. 3 is an exploded perspective view of the laser medium unit shown in FIG. 2. FIG. 4 is a front view of a laser medium unit of a second embodiment. Figure 5 is an exploded perspective view of the laser medium unit shown in Figure 4. FIG. 6 is a front view of a laser medium unit of a third embodiment. FIG. 7 is a front view of a laser medium unit of a modified example. FIG. 8 is a front view of a laser medium unit of a modified example. FIG. 9 is a drawing showing the first elastic member of the deformation example. Specific details for implementing the invention

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

[0027] [First Embodiment]

[0028] As shown in FIG. 1, a laser device (1) of a first embodiment comprises 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 between them along the Z-axis direction.

[0029] The chamber (2) has a main body (21), a pair of window sections (22), an introduction section (25), and an extraction section (26). The main body (21) has an internal space (S) that accommodates a plurality of laser medium units (10A). A pair of openings (21a) and a pair of openings (21b) are formed in the main body (21). A pair of openings (21a) are opposite each other in the Z-axis direction. A pair of openings (21b) are opposite each other in the Y-axis direction.

[0030] Each window portion (22) is mounted on the main body portion (21) to cover each opening (21a). The window portion (22) includes a frame (23) and a window member (24) supported by the frame (23). The window member (24) transmits the laser light (L1) and excitation light (L2) described later.

[0031] The introduction section (25) has an introduction passage (25a). The introduction section (25) is mounted on the main body (21) so that the introduction passage (25a) communicates with the internal space (S) through an opening (21b). The introduction section (25) introduces a refrigerant (C) (e.g., a cooling gas such as low-temperature helium gas) into the internal space (S). The refrigerant (C) flows through the gap formed between adjacent laser medium units (10A) in the internal space (S). The extraction section (26) has an extraction passage (26a). The extraction section (26) is mounted on the main body (21) so that the extraction passage (26a) communicates with the internal space (S) through an opening (21b). The extraction section (26) extracts the refrigerant (C) from the internal space (S).

[0032] A laser light source (3) is positioned on one side in the Z-axis direction relative to the chamber (2) (multiple laser medium units (10A)). The laser light source (3) emits laser light (L1), which is seed light, toward the multiple laser medium units (10A). The laser light (L1) emitted from the laser light source (3) passes through the window member (24) of the window portion (22) positioned on one side in the Z-axis direction relative to the multiple laser medium units (10A) and is incident on the multiple laser medium units (10A). The laser light (L1) is amplified by each laser medium unit (10A).

[0033] A plurality of excitation light sources (4) include a pair of first excitation light sources (41) and a pair of second excitation light sources (42). A pair of first excitation light sources (41) are positioned on one side in the Z-axis direction with respect to the chamber (2) (a 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) passes through a window member (24) of a window portion (22) positioned on one side in the Z-axis direction with respect to the plurality of laser medium units (10A) and is incident on the plurality of laser medium units (10A). A pair of second excitation light sources (42) are positioned on the other side in the Z-axis direction with respect to the chamber (2) (a plurality of laser medium units (10A)). Each second excitation light source (42) emits excitation light (L2) toward a plurality of laser medium units (10A). The excitation light (L2) emitted from each second excitation light source (42) passes through a window member (24) of a window portion (22) positioned on the other side in the Z-axis direction relative to the plurality of laser medium units (10A) and is incident on the plurality of laser medium units (10A). The excitation light (L2) excites the laser medium (11) described later.

[0034] As shown in FIGS. 2 and 3, the laser medium unit (10A) comprises a laser medium (11), a retainer (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 the pair of end faces (11a, 11b) as the main face. The laser medium (11) has, for example, a disc shape. The side face (11c) of the laser medium (11) has a predetermined width in the Z-axis direction (a direction intersecting the pair of end faces (11a, 11b) of the laser medium (11). The thickness of the laser medium (11) (i.e., the width of the side face (11c) in the Z-axis direction) is, for example, several mm to several tens of mm.

[0035] 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 an emitted light. The emitted light is, for example, stimulated emission light. The stimulated emission light contributes to the optical amplification of the laser light (L1).

[0036] A retainer (12) surrounds a laser medium (11) when viewed from the Z-axis direction and retains the laser medium (11). The retainer (12) has a main body (13) and a plurality of claw portions (14). The main body (13) is shaped like a plate, for example. The main body (13) has an inner surface (13a) and an outer surface (13b). In the first embodiment, the inner surface (13a) of the main body (13) forms the inner surface (12a) of the retainer (12), and the outer surface (13b) of the main body (13) forms the outer surface (12b) of the retainer (12).

[0037] The inner surface (13a) is extended along the side (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 a rectangular shape when viewed from the Z-axis direction, for example. Each of the inner surface (13a) and the outer surface (13b) of the main body (13) has a predetermined width in the Z-axis direction (the thickness direction of the main body (13)). The thickness of the main body (13) (i.e., the width of each of the inner surface (13a) and the outer surface (13b) in the Z-axis direction) is, for example, several mm to several tens of mm. The thickness of the main body (13) is approximately the same as the thickness of the laser medium (11). The thermal expansion rate of the main body (13) is greater than the thermal expansion rate of the laser medium (11). The material of the main body (13) is, for example, copper, etc.

[0038] A pair of locking parts (14) are provided on one side of the main body (13). Likewise, a pair of locking parts (14) are provided on the other side of the main body (13). On each side of the main body (13) and the other side, the pair of locking parts (14) face each other with the inner area of ​​the main body (13) in between when viewed from the Z-axis direction. On each side of the main body (13) and the other side, each locking part (14) protrudes inward toward the main body (13) beyond the inner surface (13a) when viewed from the Z-axis direction.

[0039] The main body (13) surrounds the laser medium (11) when viewed from the Z-axis direction. That is, the laser medium (11) is positioned inside the main body (13). When viewed from the Z-axis direction, the diameter of the laser medium (11) is approximately the same as the diameter of the inner surface (13a) of the main body (13). The movement of the laser medium (11) in a direction perpendicular to the Z-axis direction is restricted by the main body (13). The laser medium (11) is held in place by a plurality of locking parts (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 parts (14). In this way, the laser medium (11) is maintained inside the main body (13) by the main body (13) and the plurality of locking parts (14).

[0040] The laser medium (11) and the retainer (12) are in contact with each other. The laser medium (11) and the retainer (12) are in direct contact without any other materials (e.g., materials with poor thermal conductivity) in between. Specifically, the side surface (11c) of the laser medium (11) and the inner surface (13a) of the main body (13) are in contact with each other. The contact area (R) with the laser medium (11) in the retainer (12) has a predetermined width in the Z-axis direction. The width of the contact area (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 even 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 (13) corresponds to the contact area (R). That is, the width of the contact area (R) in the Z-axis direction is approximately equal to the thickness of the laser medium (11).

[0041] The contact area (R) extends along the side (11c) of the laser medium (11) when viewed from the Z-axis direction. That is, the contact area (R) extends along the outer edge of the laser medium (11) when viewed from the Z-axis direction. The contact area (R) is not separated from the outer edge of the laser medium (11) when viewed from the Z-axis direction. The side (11c) of the laser medium (11) and the contact area (R) are a single continuous surface. No concave portions, such as holes, are formed in the side (11c) and the contact area (R). There is no space between the side (11c) and the contact area (R). The laser medium (11) and the retainer (12) are in continuous contact without gaps in the contact area (R). The laser medium (11) and the retainer (12) are in close contact with each other in the contact area (R).

[0042] The main body (13) includes a plurality of deformation-allowing portions (131) that allow deformation of the main body (13). Each deformation-allowing portion (131) extends from the inner side to the outer side of the retainer (12) when viewed from the Z-axis direction. Each deformation-allowing portion (131) is a slit (13c). Each slit (13c) extends from the inner side to the outer side of the retainer (12) when viewed from the Z-axis direction. Each slit (13c) extends to the inner surface (13a) and the outer surface (13b) of the main body (13). By this, the main body (13) is divided into a plurality of main body members (132). The plurality of slits (13c) are arranged at equal intervals when viewed from the Z-axis direction. As an example, each slit (13c) is extended toward the inner surface (13a) from a position approximately in the center of each edge of the outer surface (13b) of the main body (13) when viewed from the Z-axis direction.

[0043] When viewed from the Z-axis direction, the width of each slit (13c) is sufficiently small relative to the length of the inner surface (13a) (side surface (11c) of the laser medium (11)) of the main body (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 (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 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 area (R) in the Z-axis direction. The width of the slit (13c) when viewed from the Z-axis direction is, for example, several hundred μm to several mm.

[0044] The first elastic member (15) is positioned in each slit (13c). The first elastic member (15) is composed, for example, of a plurality of overlapping wire-shaped elastic bodies. The material of the first elastic member (15) is, for example, copper. The first elastic member (15) is, for example, a copper mesh. The first elastic member (15) is fixed to the side of each main body member (132) constituting the slit (13c), for example by welding or soldering. The plurality of main body members (132) are held integrally by the first elastic member (15). The inner surface (13a) of the main body part (13) is in contact with the side (11c) of the laser medium (11) by the elastic force of the first elastic member (15). Specifically, when the inner surface (13a) of the main body (13) is in contact with the side surface (11c) of the laser medium (11), the first elastic member (15) is stretched. A plurality of main body members (132) are brought closer together by the elastic force of the first elastic member (15).

[0045] As described above, in the laser medium unit (10A), the retainer (12) that holds the laser medium (11) includes a deformation-allowing portion (131) that extends from the inner side to the outer side of the retainer (12). By this, even if the laser medium unit (10A) cools and the retainer (12) contracts, the stress generated in the laser medium (11) due to the contraction of the retainer (12) can be relieved, thereby suppressing the deterioration of the laser medium (11) characteristics caused by stress birefringence. In addition, the contact area (R) with the laser medium (11) in the retainer (12) has a width in the Z-axis direction and extends along the side (11c) of the laser medium (11) when viewed from the Z-axis direction. That is, there is no space between the contact area (R) of the retainer (12) and the side (11c) of the laser medium (11). The retainer (12) and the laser medium (11) are in close contact with each other in the contact area (R). Additionally, when viewed from the Z-axis direction, the width of each slit (13c) is sufficiently small relative to the length of the inner surface (13a) of the main body (13). By doing so, heat generated in the laser medium (11) can be efficiently dissipated to the retainer (12), thereby suppressing the degradation of the laser medium (11)'s characteristics caused by thermal birefringence and facilitating temperature control of the laser medium (11). Since the laser medium (11) may have a tendency to accumulate heat, it is particularly important to efficiently cool the laser medium (11). According to the above configuration, heat from the laser medium (11) can be efficiently dissipated, thereby suppressing the degradation of the laser medium (11)'s characteristics or the destabilization of the laser medium (11)'s characteristics. According to the above, the laser medium unit (10A) can sufficiently suppress both the degradation of the laser medium (11) characteristics caused by stress birefringence and the degradation of the laser medium (11) characteristics caused by thermal birefringence, and also facilitate temperature control of the laser medium (11).

[0046] In the laser medium unit (10A), the laser medium (11) has a plate shape with each of the pair of cross-sections (11a, 11b) as the main surface. When the laser medium (11) has a plate shape, there is a concern that it may be difficult to secure the contact area (R) with the laser medium (11) in the retainer (12) compared to, for example, when the laser medium has a rod shape. Therefore, when the laser medium (11) has a plate shape, the configuration of the retainer (12) described above is particularly effective. In addition to the contact area (R) with the laser medium (11) in the retainer (12), heat generated from the laser medium (11) can also be efficiently discharged from the pair of cross-sections (11a, 11b) of the laser medium (11).

[0047] In the laser medium unit (10A), the deformation allowable portion (131) includes a slit (13c) that extends from the inner side to the outer side of the retainer (12) when viewed from the Z-axis direction. By doing so, it is possible to easily and reliably obtain a retainer capable of relieving stress generated in the laser medium (11) due to the contraction of the retainer (12) and efficiently discharging heat generated in the laser medium (11) into the retainer.

[0048] In the laser medium unit (10A), a plurality of slits (13c) are arranged at equal intervals when viewed from the Z-axis direction. By doing so, the stress generated in the laser medium (11) due to the contraction of the retainer (12) can be uniformly relieved, and the heat generated in the laser medium (11) can be uniformly released into the retainer (12).

[0049] The laser medium unit (10A) is provided with a first elastic member (15). The first elastic member (15) is disposed in each of the plurality of slits (13c). By this, even if the retainer (12) is divided by the plurality of slits (13c), the retainer (12) can be properly brought into contact with the laser medium (11).

[0050] According to the laser device (1), as described above, both the degradation of the laser medium (11) due to stress birefringence and the degradation of the laser medium (11) due to thermal birefringence can be sufficiently suppressed, and the temperature control of the laser medium (11) can be facilitated.

[0051] The laser device (1) is equipped with a chamber (2). The chamber (2) accommodates a laser medium unit (10A). A coolant (C) flows through the chamber (2). By doing so, the laser medium unit (10A) can be cooled efficiently.

[0052] In the laser device (1), each of the plurality of laser medium units (10A) is arranged with a gap through which a coolant (C) flows. By doing so, the plurality of laser medium units (10A) can be cooled efficiently.

[0053] The laser device (1) is equipped with a laser light source (3) and an excitation light source (4). The laser light source (3) emits laser light (L1) that is amplified by a laser medium unit (10A). The excitation light source (4) emits excitation light (L2) that excites the laser medium (11). By doing so, the laser light (L1) can be amplified with good characteristics.

[0054] In the laser device (1), a first excitation light source (41) is positioned on one side in the Z-axis direction relative to the laser medium unit (10A), and a second excitation light source (42) is positioned on the other side in the Z-axis direction relative to the laser medium unit (10A). By doing so, the laser light (L1) can be amplified with better characteristics.

[0055] [Second Embodiment]

[0056] As shown in FIGS. 4 and 5, the laser medium unit (10B) of the second embodiment is mainly different from the laser medium unit (10A) of the first embodiment in that it has a retainer (12B) instead of a retainer (12), has a mounting member (16), and does not have a first elastic member (15).

[0057] The laser medium unit (10B) is equipped with a retainer (12B). The retainer (12B) has a pair of main body parts (13A, 13B). The main body part (13A) corresponds to a part of one side in the Z-axis direction of the main body part (13) of the first embodiment. The main body part (13B) corresponds to a part of the other side in the Z-axis direction of the main body part (13) of the first embodiment.

[0058] Specifically, each main body part (13A, 13B) has an inner surface (13a) and an outer surface (13b). The thickness of each main body part (13A, 13B) is about half the thickness of the main body part (13) of the first embodiment. A pair of locking parts (14) are provided on one side of the main body part (13A). A pair of locking parts (14) are provided on the other side of the main body part (13B). A laser medium (11) is sandwiched between the main body part (13A) and the main body part (13B) in the Z-axis direction. Each main body part (13A, 13B) includes a plurality of deformation-allowing parts (131). Each deformation-allowing part (131) is a slit (13c). When the laser medium (11) is sandwiched between the main body part (13A) and the main body part (13B), the main body part (13A, 13B) has the same configuration as the main body part (13) of the first embodiment. In the second embodiment, the first elastic member (15) is not placed in each slit (13c).

[0059] The laser medium unit (10B) is provided with a mounting member (16). The mounting member (16) surrounds the retainer (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. In the first mounting member (161), a first stepped portion (16c) and a second stepped portion (16d) are formed between the inner edge (16a) and the outer edge (16b). The first stepped portion (16c) has, for example, a rectangular shape when viewed from the Z-axis direction. The second stepped portion (16d) is located on the outside of the first stepped portion (16c) when viewed from the Z-axis direction. The second step portion (16d) extends along the Y-axis direction when viewed from the Z-axis direction and also reaches the outer edge (16b) of the first mounting member (161).

[0060] The second mounting member (162) has, for example, a rectangular frame shape. The inner edge (16e) of the second mounting member (162) roughly 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) roughly coincides with the second stepped portion (16d) of the first mounting member (161) when viewed from the Z-axis direction. The second mounting member (162) is positioned on the second stepped portion (16d) of the first mounting member (161).

[0061] The outer surface (13b) of a pair of main body parts (13A, 13B) is located further outward than the inner edge (16a) of the first mounting member (161) and the inner edge (16e) of the second mounting member (162) when viewed from the Z-axis direction, and is approximately aligned with the first stepped portion (16c). The laser medium (11) and the retainer (12B) are placed in the first stepped portion (16c) and are sandwiched between the first mounting member (161) and the second mounting member (162). In this way, the retainer (12B) is held together by the mounting member (16).

[0062] As described above, the laser medium unit (10B) is equipped with a mounting member (16). The mounting member (16) surrounds the retainer (12B) when viewed from the Z-axis direction. By this, even if the retainer (12) is divided by a plurality of slits (13c), the retainer (12) can be properly brought into contact with the laser medium (11).

[0063] [Third Embodiment]

[0064] As shown in FIG. 6, the laser medium unit (10C) of the third embodiment is mainly different from the laser medium unit (10A) of the first embodiment in that it has a laser medium (11C) instead of a laser medium (11), has a retainer (12C) instead of a retainer (12), does not have a first elastic member (15), has a mounting member (18) further, and has a second elastic member (19) further.

[0065] The laser medium unit (10C) is equipped with a laser medium (11C). The laser medium (11C) has a light amplification region (111) and a light absorption region (112). The light amplification region (111) is, for example, YAG doped with Yb as an active element. The light amplification region (111) is, for example, in the shape of a disc. The light absorption region (112) surrounds the light amplification region (111) when viewed from the Z-axis direction. The light absorption region (112) is formed integrally with the light amplification region (111). The light absorption region (112) suppresses the occurrence of parasitic oscillation by absorbing a portion of the emitted light generated from the light amplification region (111). The outer surface of the light absorption region (112) constitutes the side surface (11c) of the laser medium (11C). The material of the light absorption region (112) is, for example, Cr:YAG ceramics, Sm:YAG, black ink or black resin, etc.

[0066] The laser medium unit (10C) is provided with a retainer (12C). The retainer (12C) has a main body (13) and a stress relief portion (17). The stress relief portion (17) is provided on the inner surface (13a) of the main body (13). That is, the stress relief portion (17) is provided between the laser medium (11C) and the main body (13). The stress relief portion (17) has a ring shape. The stress relief portion (17) has a predetermined width in the Z-axis direction. The width of the stress relief portion (17) in the Z-axis direction is, for example, several mm to several tens of mm. The width of the stress relief portion (17) in the Z-axis direction is approximately the same as the thickness of the laser medium (11C). The stress relief portion (17) is extended along the side (11c) of the laser medium (11C) when viewed from the Z-axis direction. The stress relief portion (17) is continuously connected when viewed from the Z-axis direction. For example, a notch or similar structure may be formed locally in the stress relief portion (17). For example, the notch may be formed at a position corresponding to the slit (13c) of the main body portion (13) and may have a width approximately equal to that of the slit (13c).

[0067] The laser medium (11C) and the retainer (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 relief part (17) are in contact with each other. In the third embodiment, the inner surface (17a) of the stress relief part (17) constitutes the inner surface (12a) of the retainer (12). In the third embodiment, the inner surface (17a) of the stress relief part (17) corresponds to the contact area (R). The elastic modulus of the stress relief part (17) is smaller than the elastic modulus of the main body (13). The thermal conductivity of the stress relief part (17) is greater than the thermal conductivity of the laser medium (11C). The absolute value of the difference between the thermal conductivity of the stress relief part (17) and the thermal conductivity of the main body part (13) is smaller than the absolute value of the difference between the thermal conductivity of the stress relief part (17) and the thermal conductivity of the laser medium (11C). That is, the thermal conductivity of the stress relief part (17) is closer to that of the main body part (13) than to that of the laser medium (11C). The material of the stress relief part (17) is, for example, indium.

[0068] The laser medium unit (10C) is provided with a mounting member (18). The mounting member (18) surrounds the retainer (12C) when viewed from the Z-axis direction. When viewed from the Z-axis direction, the mounting member (18) has, for example, a rectangular frame shape. The inner surface (18a) of the mounting member (18) is located further outward than the outer surface (13b) of the main body (13) when viewed from the Z-axis direction. The thermal expansion rate of the mounting member (18) is smaller than the thermal expansion rate of the main body (13). The material of the mounting member (18) is, for example, stainless steel.

[0069] The laser medium unit (10C) is provided with a second elastic member (19). The second elastic member (19) is positioned between the main body (13) and the mounting member (18). The second elastic member (19) is extended along the outer surface (13b) of the main body (13) when viewed from the Z-axis direction. Like 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. 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 soldering.

[0070] A plurality of main body members (132) of the main body part (13) are held together by a mounting member (18) and a second elastic member (19). The inner surface (17a) of the stress relief part (17) is in contact with 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. A 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 relief part (17) is in contact with the side surface (11c) of the laser medium (11C) by being pressed against the plurality of main body members (132). Also, in FIG. 6, the illustration of the locking part (14) is omitted.

[0071] As described above, in the laser medium unit (10C), the retainer (12C) has a main body (13) and a stress relief part (17). The main body (13) includes a deformation allowance part (131). The stress relief part (17) is provided between the laser medium (11C) and the main body (13). By this, the stress generated in the laser medium (11C) due to the contraction of the retainer (12C) can be relieved more effectively, thereby more effectively suppressing the degradation of the laser medium (11C) characteristics caused by stress birefringence. In addition, since the elastic modulus of the stress relief part (17) is smaller than the elastic modulus of the main body (13), the adhesion between the laser medium (11C) and the retainer (12C) can be improved. By this, heat generated in the laser medium (11C) can be dissipated more efficiently into the retainer (12C).

[0072] In the laser medium unit (10C), the laser medium (11C) has a light amplification region (111) and a light absorption region (112) surrounding the light amplification region (111) when viewed from the Z-axis direction. As a result, since a portion of the emitted light generated in the light amplification region (111) is absorbed by the light absorption region (112), the occurrence of parasitic oscillation is suppressed. Furthermore, since heat is generated in the light absorption region (112) by the absorption of a portion of the emitted light, the configuration of the above-described retainer (12C) is particularly effective. Additionally, when the laser medium (11C) has a plate shape, cooling from the cross-section, which is the main surface of the laser medium (11C) (cross-section cooling) is the mainstream (general), and cooling from the side (11c) of the laser medium (11C) (side cooling) tends not to receive attention. In addition, if the laser medium (11C) has a light absorption region (112) that suppresses parasitic oscillation, heat generation is particularly high on the side (11c) of the laser medium (11C). Therefore, according to the configuration of the above-described retainer (12C), cross-sectional cooling by a refrigerant such as a cooling gas, and side-sectional cooling by the retainer (12C) become possible. By doing so, heat generated in the laser medium (11C) can be efficiently removed, thereby effectively suppressing the degradation of the laser characteristics of the laser medium (11C).

[0073] The laser medium unit (10C) is provided with a second elastic member (19) disposed between the retainer (12C) and the mounting member (18). By this, even if the retainer (12C) is divided by a plurality of slits (13c), the retainer (12C) can be properly brought into contact with the laser medium (11C).

[0074] In the laser medium unit (10C), the thermal expansion rate of the mounting member (18) is smaller than the thermal expansion rate of the main body (13). As a result, when the laser medium unit (10C) is cooled, the amount of shrinkage of the mounting member (18) is smaller than the amount of shrinkage of the retainer (12C). However, by means of the second elastic member (19) positioned between the retainer (12C) and the mounting member (18), the difference between the amount of shrinkage of the mounting member (18) and the amount of shrinkage of the retainer (12C) can be adjusted, thereby suppressing the effect of the shrinkage of the mounting member (18) on the laser medium (11C).

[0075] [Variation Example]

[0076] Although each embodiment of the present disclosure has been described above, the present disclosure is not limited to the embodiments described above.

[0077] In the third embodiment, an example was disclosed in which the outer surface (13b) of the main body (13) has a rectangular shape when viewed from the Z-axis direction, but as shown in FIG. 7, the main body (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. In addition, a second elastic member (19) does not need to be placed between the retainer (12D) and the mounting member (18D). In this case, the thermal expansion rate of the mounting member (18D) is greater than the thermal expansion rate of the main body (13D). By this, when the mounting member (18D) is cooled, the retainer (12D) can be held by the contraction of the mounting member (18D), and the retainer (12D) can be properly brought into contact with the laser medium (11C). Additionally, as shown in FIG. 8, the main body (13E) may include one slit (13c) (deformation allowance part (131)).

[0078] In the first embodiment, an example was disclosed in which the first elastic member (15) is composed of a plurality of overlapping wire-shaped elastic bodies, but as shown in FIG. 9, the first elastic member (15) may be, for example, a spring. In the third embodiment, the second elastic member (19) may also be, for example, a spring. Each of the first elastic member (15) and the second elastic member (19) may be composed of, for example, an elastic resin such as an elastic adhesive.

[0079] In each embodiment, an example has been disclosed in which the laser medium (11, 11C) has a plate shape, but the laser medium (11, 11C) may have a rod shape, for example. Additionally, an example has been disclosed in which the laser medium (11, 11C) has a disc shape, but the laser medium (11, 11C) may have a rectangular plate shape, for example.

[0080] In each embodiment, an example has been disclosed in which the slit (13c) reaches the inner surface (13a) and the outer surface (13b) of the main body (13, 13A, 13B), but the slit (13c) does not have to reach the inner surface (13a) and the outer surface (13b) of the main body (13, 13A, 13B). The slit (13c) may reach either the inner surface (13a) or the outer surface (13b) of the main body (13, 13A, 13B), or it 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 (13, 13A, 13B).

[0081] In each embodiment, an example is disclosed in which each deformation allowable portion (131) is a slit (13c), but the deformation allowable portion (131) does not have to be a slit (13c). The deformation allowable portion (131) may be, for example, a first region among the retainers (12, 12B, 12C). The elastic modulus of the first region may be smaller than the elastic modulus of the second region among the retainers (12, 12B, 12C). Additionally, the deformation allowable portion (131) may be, for example, a first region among the retainers (12, 12B, 12C). The thickness in the Z-axis direction of the first region may be smaller than the thickness in the Z-axis direction of the second region among the retainers (12, 12B, 12C). That is, the deformation allowable portion (131) does not have to penetrate the retainers (12, 12B, 12C) in the Z-axis direction. The deformation allowable portion (131) only needs to allow deformation of the retainer (12, 12B, 12C).

[0082] Each of the laser medium unit (10A) of the first embodiment and the laser medium unit (10B) of the second embodiment may also have a retainer (12C) having a stress relief portion (17), just like the laser medium unit (10C) of the third embodiment.

[0083] Each of the laser medium unit (10A) of the first embodiment and the laser medium unit (10B) of the second embodiment may also have a laser medium (11C) having a light amplification region (111) and a light absorption region (112), similar to the laser medium unit (10C) of the third embodiment.

[0084] In the third embodiment, an example is disclosed in which the light absorption region (112) is formed integrally with the light amplification region (111), but the light absorption region (112) may be formed separately from the light amplification region (111). The light absorption region (112) may be provided on the side of the light amplification region (111) as a separate member.

[0085] In the third embodiment, an example is disclosed in which the thermal expansion rate of the mounting member (18) is smaller than the thermal expansion rate of the main body (13), but the thermal expansion rate of the mounting member (18) may be larger than the thermal expansion rate of the main body (13). In this case, when the laser medium unit (10C) is cooled, the amount of shrinkage of the mounting member (18) becomes greater than the amount of shrinkage of the retainer (12C). However, by means of the second elastic member (19) disposed between the retainer (12C) and the mounting member (18), the difference between the amount of shrinkage of the mounting member (18) and the amount of shrinkage of the retainer (12C) can be adjusted, thereby suppressing the effect of the shrinkage of the mounting member (18) on the laser medium (11C). Explanation of the symbols

[0086] 1: Laser device 2: Chamber 3: Laser light source 4: Excitation light source 10A, 10B, 10C: Laser medium units 11, 11C: Laser medium 11a, 11b: Cross-section 11c: Side view 12, 12B, 12C, 12D: Retainers 13, 13A, 13B, 13D: Main body 13c: Slit 15: First elastic member 16, 18, 18D: Mounting members 17: Stress relief section 19: Second elastic member 41: First excitation light source 42: Second excitation light source 111: Light amplification region 112: Light absorption region 131: Deformation allowance region C: Refrigerant

Claims

Claim 1 A laser medium unit comprising a laser medium having a pair of cross-sections, and a retaining body that surrounds the laser medium when viewed from a direction intersecting the pair of cross-sections and holds the laser medium, wherein the laser medium has a plate shape with each of the pair of cross-sections as its main surface, and the retaining body includes a deformation-allowing portion that extends from the inside to the outside of the retaining body when viewed from the direction intersecting the pair of cross-sections, wherein the laser medium and the retaining body are in contact with each other, and the contact area with the laser medium in the retaining body has a width in the direction intersecting the pair of cross-sections and extends along the outer edge of the laser medium when viewed from the direction intersecting the pair of cross-sections, and wherein the retaining body has a main body portion including the deformation-allowing portion and a stress-relieving portion provided between the laser medium and the main body portion, wherein the deformation-allowing portion is not formed as the same member as the stress-relieving portion. Claim 2 A laser medium unit according to claim 1, wherein the laser medium comprises a light amplification region and a light absorption region surrounding the light amplification region when viewed from the direction intersecting the pair of cross-sections. Claim 3 A laser medium unit according to claim 1, wherein the deformation-allowing portion comprises a slit extending from the inner side to the outer side of the retainer when viewed from the direction intersecting the pair of cross-sections. Claim 4 A laser medium unit according to claim 2, wherein the deformation-allowing portion comprises a slit extending from the inner side to the outer side of the retainer when viewed from the direction intersecting the pair of cross-sections. Claim 5 A laser medium unit according to claim 3, wherein each of the slits is a plurality of slits, and the plurality of slits are arranged at equal angular intervals when viewed from the direction intersecting the pair of cross-sections. Claim 6 A laser medium unit according to claim 4, wherein each of the slits is a plurality of slits, and the plurality of slits are arranged at equal angular intervals when viewed from the direction intersecting the pair of cross-sections. Claim 7 A laser medium unit according to any one of claims 3 to 6, further comprising a first elastic member, wherein each of the slits is a plurality of slits, and the first elastic member is disposed in each of the plurality of slits. Claim 8 A laser medium unit according to any one of claims 3 to 6, further comprising a mounting member, wherein each of the slits is a plurality of slits, and the mounting member surrounds the retainer when viewed from the direction intersecting the pair of cross-sections. Claim 9 A laser medium unit according to claim 7, further comprising a mounting member, wherein each of the slits is a plurality of slits, and the mounting member surrounds the retainer when viewed from the direction intersecting the pair of cross-sections. Claim 10 A laser medium unit according to claim 8, further comprising a second elastic member disposed between the retainer and the mounting member. Claim 11 A laser medium unit according to claim 9, further comprising a second elastic member disposed between the retainer and the mounting member. Claim 12 A laser medium unit according to claim 10, wherein the thermal expansion rate of the mounting member is smaller than the thermal expansion rate of the retainer. Claim 13 A laser medium unit according to claim 11, wherein the thermal expansion rate of the mounting member is smaller than the thermal expansion rate of the retainer. Claim 14 A laser medium unit according to claim 10, wherein the thermal expansion rate of the mounting member is greater than the thermal expansion rate of the retainer. Claim 15 A laser medium unit according to claim 11, wherein the thermal expansion rate of the mounting member is greater than the thermal expansion rate of the retainer. Claim 16 A laser device comprising a laser medium unit as described in claim 1. Claim 17 A laser device according to claim 16, further comprising a chamber that accommodates the laser medium unit and through which a coolant flows. Claim 18 A laser device according to claim 17, wherein each of the laser medium units is a plurality of laser medium units, and each of the plurality of laser medium units is arranged with a gap through which the refrigerant flows. Claim 19 A laser device according to any one of claims 16 to 18, further comprising a laser light source that emits laser light amplified by the laser medium unit and an excitation light source that emits excitation light that excites the laser medium. Claim 20 A laser device according to claim 19, wherein the excitation light source is each a first excitation light source and a second excitation light source, wherein the first excitation light source is disposed on one side in the direction intersecting the pair of cross-sections with respect to the laser medium unit, and the second excitation light source is disposed on the other side in the direction intersecting the pair of cross-sections with respect to the laser medium unit.

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