Laser medium unit, laser amplifier, and laser oscillator

Abstract

To provide a laser medium unit, a laser amplification device, and a laser oscillation device that can improve assemblability while reducing thermal lensing effects.SOLUTION: A laser medium unit 2 includes a laser gain medium 10 that is formed in a plate shape, has a first surface 10a and a second surface 10b, which is opposite to the first surface 10a, and generates emitted light upon irradiation of excitation light L1 from the first surface 10a and a light guiding and cooling member 20 that is connected to the first surface 10a and guides the excitation light L1 toward the first surface 10a and cools the laser gain medium 10. The first surface 10a includes a first area R1 to which the light guiding and cooling member 20 is thermally connected and a second area R2 other than the first area R1. The entire second area R2 is thermally shielded from the light guiding and cooling member 20.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a laser medium unit, a laser amplifier, and a laser oscillator. [Background technology]

[0002] Patent Document 1 describes a laser medium unit. This laser medium unit includes a plate-shaped laser gain medium that generates emitted light when irradiated with pumping light from a first surface, and a cooling member thermally connected to a second surface of the laser gain medium opposite the first surface. In this laser medium unit, the cooled area formed on the second surface by the cooling member is set to an area equal to or smaller than the area irradiated with pumping light in the laser gain medium, thereby reducing the thermal lens effect caused by a temperature gradient. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-129391 Summary of the Invention [Problem to be solved by the invention]

[0004] In the laser medium unit as described above, it is necessary to connect the cooling member to the laser gain medium so that the area cooled by the cooling member is equal to or smaller than the irradiation area of ​​the pumping light, and for example, when the laser gain medium is made compact, high precision is required in assembling the cooling member and the laser gain medium.

[0005] An object of the present invention is to provide a laser medium unit, a laser amplifier, and a laser oscillator that can reduce the thermal lens effect and improve assembly efficiency. [Means for solving the problem]

[0006] The laser medium unit of the present invention comprises a laser gain medium formed in a plate shape and having a first surface and a second surface opposite to the first surface, the laser gain medium generating emitted light when irradiated with pumping light from the first surface, and a light-guiding cooling member connected to the first surface, guiding the pumping light toward the first surface and cooling the laser gain medium, the first surface comprising a first region to which the light-guiding cooling member is thermally connected, and a second region other than the first region, and the entire second region is thermally insulated from the light-guiding cooling member.

[0007] In this laser medium unit, a light-guiding cooling member is connected to the first surface of the laser gain medium, and the light-guiding cooling member guides the pumping light toward the first surface and cools the laser gain medium. This ensures that the pumping light irradiation area and the cooling area on the first surface coincide with each other, thereby reliably reducing the thermal lens effect. Furthermore, since the irradiation area and the cooling area can be aligned simply by connecting the light-guiding cooling member to the laser gain medium, assembly is easier than, for example, connecting the cooling member to the laser gain medium so that the cooling area is located within a predetermined irradiation area. Furthermore, in this laser medium unit, the first surface of the laser gain medium includes a first area thermally connected to the light-guiding cooling member and a second area other than the first area, and the entire second area is thermally insulated from the light-guiding cooling member. This prevents the temperature distribution in the second area in a direction parallel to the first surface from becoming non-uniform, thereby preventing the thermal lens effect caused by the non-uniform temperature distribution in the second area. Therefore, this laser medium unit reduces the thermal lens effect and improves assembly. Furthermore, in this laser medium unit, the light-guiding cooling member connected to the first surface can guide the pump light toward the first surface and cool the laser gain medium, thereby simplifying the configuration on the second surface side and increasing the degree of freedom in arranging the members.

[0008] The second region may surround the first region, which can prevent the temperature distribution in the second region in a direction parallel to the first surface from becoming uneven, thereby further reducing the thermal lens effect.

[0009] When viewed from a direction perpendicular to the first surface, the first region may have a shape that is line-symmetric with respect to a line passing through the center of the first surface and point-symmetric with respect to the center. In this case, the temperature distribution in the first region in a direction parallel to the first surface can be made uniform, and the thermal lens effect can be further reduced.

[0010] The light-guiding and cooling member may have a light-guiding section connected to the first surface and a cooling section in contact with a side surface of the light-guiding section. In this case, the light-guiding section can guide the pump light toward the first surface, and the cooling section can effectively cool the laser gain medium via the light-guiding section.

[0011] The light-guiding cooling member may have a light-guiding section connected to the first surface, and the light-guiding section may be configured to homogenize the intensity distribution of the excitation light in a direction parallel to the first surface when the excitation light is guided by the light-guiding section. In this case, the first surface can be irradiated with excitation light whose intensity distribution in the direction parallel to the first surface has been homogenized, thereby further reducing the thermal lens effect. Furthermore, because the intensity distribution of the excitation light can be homogenized by the light-guiding cooling member, the configuration can be simplified compared to, for example, a case in which a separate member for homogenizing the intensity distribution of the excitation light is provided.

[0012] The light-guiding cooling member may have a light-guiding section connected to the first surface, and the length of the light-guiding section in a direction perpendicular to the first surface may be longer than the length of the light-guiding section in a direction parallel to the first surface. In this case, the light-guiding section can effectively homogenize the intensity distribution of the excitation light.

[0013] The laser medium unit of the present invention may further include a light source that outputs pumping light, and the light source may be a semiconductor laser having a plurality of light-emitting regions. In this case, the intensity of the pumping light can be increased.

[0014] A layer that transmits pump light but reflects emitted light may be formed on the first surface, allowing the pump light to enter the laser gain medium from the first surface side while reflecting the emitted light toward the second surface side.

[0015] The light-guiding cooling member may have a layer formed on its surface on which the pumping light is incident, which layer transmits the pumping light and reflects the emitted light. In this case, the pumping light is allowed to enter the laser gain medium from the first surface side, while the emitted light is reflected toward the second surface side.

[0016] The second surface may be provided with a layer that reflects the excitation light but transmits the emitted light, thereby preventing the excitation light from passing through the second surface and allowing the emitted light to exit through the second surface.

[0017] A plurality of laser gain media and a plurality of light-guiding cooling members may be provided, and the plurality of laser gain media and the plurality of light-guiding cooling members may be connected alternately. In this case, the pumping light can be absorbed by the plurality of laser gain media, and the absorption efficiency of the pumping light can be improved. Furthermore, when the light-guiding cooling members are connected to both sides (the first surface side and the second surface side) of the laser gain medium, the laser gain medium can be pumped and cooled from both sides.

[0018] The laser medium unit of the present invention may further include a plurality of light sources each outputting pumping light, and the pumping light from each of the plurality of light sources may be incident on the light-guiding cooling member. In this case, the intensity of the pumping light can be increased.

[0019] The light-guiding cooling member may have a light-guiding section connected to the first surface, and the outer peripheral surface of the light-guiding section may be formed in a tapered shape that is inclined with respect to a direction perpendicular to the first surface. In this case, the excitation light is likely to be repeatedly reflected by the inner surface of the light-guiding section, and the intensity distribution of the excitation light can be effectively uniformed by the light-guiding section.

[0020] The laser medium unit of the present invention may further include a housing having a vacuum internal space, and the laser gain medium and the light-guiding cooling member may be disposed in the internal space. In this case, when the laser gain medium is cooled to a low temperature, for example, 0°C or lower, it is possible to prevent condensation from occurring on the laser gain medium, etc.

[0021] The light-guiding cooling member may have a light-guiding portion connected to the first surface, the light-guiding portion being formed in a cylindrical shape and defining a flow path therein for a coolant to flow in. In this case, the laser gain medium can be effectively cooled by flowing the coolant through the flow path.

[0022] The laser amplifier of the present invention includes the laser medium unit described above, and laser light is incident on the first surface or the second surface, and the laser light is amplified by the emitted light in the laser gain medium and output. With this laser amplifier, for the reasons described above, it is possible to reduce the thermal lens effect and improve assembly ease.

[0023] Laser light may be incident on the second surface and the amplified laser light may be output from the second surface. In this case, the laser light travels back and forth within the laser gain medium, thereby increasing the interaction length contributing to the amplification of the laser light and improving the efficiency of extracting light energy.

[0024] The laser amplifier of the present invention may include a plurality of the above-described laser medium units, wherein in each of the plurality of laser medium units, laser light is incident on the second surface, and the laser light amplified by the emitted light in the laser gain medium is emitted from the second surface, and the plurality of laser medium units may include a first laser medium unit and a second laser medium unit, and the laser light emitted from the first laser medium unit may be amplified in the second laser medium unit. In this case, the laser light can be effectively amplified by the plurality of laser medium units.

[0025] The laser oscillator of the present invention includes the laser medium unit described above and a partial reflector disposed on the optical path of the emitted light output from the laser gain medium, which causes the emitted light to oscillate into a laser beam. For the reasons described above, this laser oscillator can reduce the thermal lens effect and improve assembly ease. [Effects of the Invention]

[0026] According to the present invention, it is possible to provide a laser medium unit, a laser amplifier, and a laser oscillator that can reduce the thermal lens effect and improve the ease of assembly. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a perspective view of a laser amplifier according to an embodiment. [Figure 2] FIG. 1 is a plan view of a laser amplifier device. [Figure 3] FIG. 2 is a perspective view of a laser medium unit. [Figure 4] FIG. 2 is a plan view of a laser medium unit. [Figure 5] FIG. 2 is another plan view of the laser medium unit. [Figure 6] FIG. 2 illustrates a first surface of a laser gain medium. [Figure 7] FIG. 1(a) is a diagram showing a flat-top intensity distribution, and FIG. 1(b) is a diagram showing a Gaussian intensity distribution. [Figure 8] FIG. 10 is a plan view of a laser medium unit according to a first modified example. [Figure 9] FIG. 10 is a plan view of a laser medium unit according to a second modified example. [Figure 10] FIG. 10 is a plan view of a laser medium unit according to a third modified example. [Figure 11] FIG. 10 is a plan view of a laser medium unit according to a fourth modified example. [Figure 12] FIG. 11 is a plan view of a laser medium unit according to a fifth modified example. [Figure 13] FIG. 13 is a plan view of a laser oscillation device according to a sixth modified example. [Figure 14] FIG. 13 is a perspective view showing a laser amplifier according to a seventh modified example. [Figure 15] FIG. 13 is a plan view showing a laser amplifier according to a seventh modified example. [Figure 16] 10(a) and 10(b) are diagrams showing other examples of the arrangement of the first and second regions. DETAILED DESCRIPTION OF THE INVENTION

[0028] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, the same or equivalent elements are designated by the same reference numerals, and redundant description will be omitted. [Laser amplifier]

[0029] 1 and 2, the laser amplifier 1 is an active mirror type laser device including a plurality of laser medium units 2 and a light transmitting member 3. In this example, the plurality of laser medium units 2 include three laser medium units 2A, 2B, and 2C. Each of the laser medium units 2A, 2B, and 2C includes a laser gain medium 10, and is connected to the light transmitting member 3 at the laser gain medium 10.

[0030] The light transmitting member 3 is made of a material that can transmit the excitation light L1 and laser light L2 (described later). The light transmitting member 3 is made of, for example, yttrium aluminum garnet (YAG). The light transmitting member 3 is not doped with an active element such as Nd (neodymium).

[0031] 2, in the laser amplifier 1, laser light L2 introduced as seed light into the light transmitting member 3 is sequentially amplified in the laser gain media 10 of the laser medium units 2A, 2B, and 2C, and the amplified laser light L2 is emitted as output light from the light transmitting member 3. First, the configuration of one laser medium unit 2 will be described below, but the laser medium units 2A, 2B, and 2C have the same configuration. [Laser medium unit]

[0032] As shown in FIGS. 3, 4, and 5, the laser medium unit 2 (laser head) includes a laser gain medium 10, a light-guiding cooling member 20, a light source 30, and a condenser lens 40. The laser gain medium 10 is made of, for example, YAG doped with Nd (neodymium) as an active element. That is, the laser gain medium 10 is doped with an active element. The active element doped in the YAG may be Yb (ytterbium). The laser gain medium 10 is excited by pumping light L1 to generate emitted light. An example of the emitted light is stimulated emission light. This stimulated emission light contributes to the optical amplification of the laser light L2.

[0033] The laser gain medium 10 is formed, for example, in a disk shape and has a first surface 10a and a second surface 10b opposite to the first surface 10a. The first surface 10a and the second surface 10b are main surfaces of the plate-shaped laser gain medium 10 and are flat surfaces parallel to each other. As an example, the diameter of the laser gain medium 10 is about 25 mm and the thickness is about 5 mm. Note that the first surface 10a and the second surface 10b do not have to extend parallel to each other; for example, the second surface 10b may be inclined at about 1 degree with respect to the first surface 10a.

[0034] As shown in Fig. 4, a first layer 11 is formed on the first surface 10a. In this example, the first layer 11 is formed on the entire surface of the first surface 10a. The first layer 11 functions as a first light selection section that transmits the excitation light L1 while reflecting the laser light L2 (emitted light). The first layer 11 is formed, for example, by applying an anti-reflection coating to the excitation light L1 and a high-reflection coating to the laser light L2 to the first surface 10a.

[0035] A second layer 12 is formed on the second surface 10b. In this example, the second layer 12 is formed on the entire surface of the second surface 10b. The second layer 12 functions as a second light selection section that reflects the excitation light L1 while transmitting the laser light L2 (emitted light). The second layer 12 is formed, for example, by applying a high-reflection coating to the excitation light L1 and an anti-reflection coating to the laser light L2 to the second surface 10b.

[0036] The light-guiding cooling member 20 has a light-guiding section 21 and a cooling section 22. The light-guiding section 21 is formed in a cylindrical shape using, for example, sapphire, quartz, or undoped YAG. In this example, the light-guiding section 21 extends along a first direction D1 perpendicular to the first surface 10a, and is connected to the first surface 10a at one end face 21a in the first direction D1. More specifically, as described above, the first layer 11 is formed on the first surface 10a, and the light-guiding section 21 is connected to the first surface 10a via the first layer 11. In this manner, in this specification, the connection of a member A to a member B includes the connection of a member A to a member B via another element.

[0037] The excitation light L1 is introduced into the light-guiding unit 21 from an end face 21b opposite to the end face 21a. The light-guiding unit 21 guides the introduced excitation light L1 toward the end face 21a (first surface 10a). The light-guiding unit 21 is configured so that, when the excitation light L1 is guided by the light-guiding unit 21, the intensity distribution of the excitation light L1 in a direction parallel to the first surface 10a is homogenized. That is, when the excitation light L1 is guided by the light-guiding unit 21, the intensity distribution of the excitation light L1 at the end face 21a (first surface 10a) is more homogenized than the intensity distribution of the excitation light L1 at the end face 21b. In this example, the excitation light L1 incident on the light-guiding unit 21 is mixed by being guided while being repeatedly reflected by the side face 21c of the light-guiding unit 21, and is then incident on the first surface 10a as light having a homogenized intensity distribution. When the transverse mode (intensity distribution in a direction parallel to the first surface 10a) of the excitation light L1 incident on the light-guiding section 21 is a single mode, the transverse mode of the excitation light L1 can be converted to a multimode by guiding the excitation light L1 through the light-guiding section 21.

[0038] In order to homogenize the intensity distribution of excitation light L1, it is advantageous for light guiding section 21 to have a large aspect ratio (the ratio of length T1 in first direction D1 to length T2 in the direction parallel to first surface 10a). Therefore, in this example, length T1 of light guiding section 21 in first direction D1 is longer than length T2 (maximum length; in this example, the diameter of light guiding section 21) of light guiding section 21 in the direction parallel to first surface 10a. That is, the aspect ratio of light guiding section 21 is greater than 1. As an example, length T1 is approximately 100 mm, and length T2 is approximately 6 mm. Thus, the aspect ratio of light guiding section 21 may be 6 or greater, or may be 10 or greater. Length T1 is the length (maximum length) of light guiding section 21 at the contact surface (end surface 21a) with first surface 10a, regardless of the shape of light guiding section 21.

[0039] The cooling unit 22 is a cooling block made of a metal material such as copper or stainless steel, and is in contact with the side surface 21c of the light-guiding unit 21. In this example, the cooling unit 22 is formed to have a through hole extending along the first direction D1, and the inner surface of the through hole is in contact with the side surface 21c of the light-guiding unit 21 along the entire periphery. The cooling unit 22 has, for example, a rectangular outer shape when viewed from the first direction D1. The cooling unit 22 faces the first surface 10a of the laser gain medium 10 in the first direction D1. In this example, the cooling unit 22 is made of a material having a higher thermal conductivity than that of the light-guiding unit 21, and cools the light-guiding unit 21 by radiating heat from the light-guiding unit 21 to the outside (air) (conduction cooling). Cooling the light-guiding unit 21 also cools the laser gain medium 10 connected to the light-guiding unit 21. That is, the cooling unit 22 cools the laser gain medium 10 via the light-guiding unit 21.

[0040] In this way, the light-guiding cooling member 20 guides the pumping light L1 toward the first surface 10a of the laser gain medium 10 by the light-guiding section 21, and cools the laser gain medium 10 via the light-guiding section 21 by the cooling section 22. FIG. 6 is a view of the first surface 10a as viewed from the first direction D1. In FIG. 6, the first region R1 to which the light-guiding section 21 is connected is indicated by hatching. As shown in FIG. 6, the first surface 10a is made up of two regions: the first region R1 and a second region R2 other than the first region R1. The first region R1 is a connected region to which the light-guiding section 21 is connected, and the second region R2 is a non-connected region to which the light-guiding section 21 is not connected.

[0041] The light-guiding cooling member 20 is thermally connected to the first region R1. On the other hand, the entire second region R2 is thermally insulated from the light-guiding cooling member 20. "The light-guiding cooling member 20 is thermally connected to the first region R1" means that heat can be transferred between the first region R1 and the light-guiding cooling member 20. "The second region R2 is thermally insulated from the light-guiding cooling member 20" means that heat is not transferred between the second region R2 and the light-guiding cooling member 20 (except for heat transfer via the first region R1). In this example, the light-guiding section 21 is thermally connected to the first region R1 via the first layer 11. The light-guiding cooling member 20 is not in contact with the second region R2, and a space is formed between the second region R2 and the cooling section 22, and air exists in this space. As a result, the entire second region R2 is thermally insulated from the light-guiding cooling member 20. Furthermore, the light-guiding section 21 is optically connected to the first region R1 via the first layer 11 (so that light can travel between the first region R1 and the light-guiding section 21). The first region R1 functions as an irradiation region where the first surface 10a is irradiated with the pumping light L1 and a cooling region where the laser gain medium 10 is cooled by the light-guiding cooling member 20. The second region R2 is a non-irradiation region where the first surface 10a is not irradiated with the pumping light L1, and also a non-cooling region where the laser gain medium 10 is not cooled by the light-guiding cooling member 20.

[0042] A member having thermal insulation properties may be interposed between the second region R2 and the cooling unit 22 (light-guiding cooling member 20). In this case, the second region R2 is also thermally insulated from the cooling unit 22. The thermal conductivity of the member may be, for example, 1.0 W / m·k or less. That is, a member having thermal conductivity of 1.0 W / m·k or less may be interposed between the second region R2 and the cooling unit 22. In this example, the laser gain medium 10 is fixed by being connected to the light-guiding unit 21 at the first surface 10a and to the light-transmitting member 3 at the second surface 10b. The laser gain medium 10 is not in contact with any member other than the light-guiding unit 21 and the light-transmitting member 3. However, the laser gain medium 10 may be supported by a member having thermal conductivity of 1.0 W / m·k or less.

[0043] 6, when viewed from the first direction D1, each of the first region R1 and the second region R2 has a shape that is line-symmetric with respect to each of straight lines LN1 and LN2 passing through the center C of the first surface 10a and point-symmetric with respect to the center C. The straight lines LN1 and LN2 are perpendicular to each other. In this example, the shape of the first region R1 is a circle corresponding to the end face 21a of the light-guiding unit 21, and the shape of the second region R2 is an annular shape that surrounds the first region R1.

[0044] The light source 30 is an excitation light source that outputs excitation light L1. The light source 30 is, for example, a semiconductor laser having multiple light-emitting regions. In this example, the light source 30 is configured as a laser diode module in which multiple rectangular plate-shaped laser diodes are stacked along a predetermined direction, and has multiple light-emitting regions formed by the end faces of the laser diodes.

[0045] The condenser lens 40 condenses the pump light L1 output from the light source 30 and guides it to the end face 21b of the light guide 21. The light incident on the end face 21b is guided by the light guide 21 toward the first surface 10a of the laser gain medium 10, passes through the first layer 11, and is incident on the first surface 10a. As shown in FIG. 4, the pump light L1 incident on the first surface 10a propagates through the laser gain medium 10 toward the second surface 10b while diverging in a direction parallel to the first surface 10a. The laser gain medium 10 generates emitted light when irradiated with the pump light L1 from the first surface 10a. The pump light L1 reaching the second surface 10b is reflected by the second layer 12 on the second surface 10b. The divergence angle at which the pump light L1 propagates from the first surface 10a toward the second surface 10b varies depending on the size of the light guide 21 and the thickness of the laser gain medium 10.

[0046] 1 and 2, the laser amplifier 1 will be described. In this example, the laser medium units 2A and 2C are connected to a surface 3a of the light transmitting member 3, and the laser medium unit 2B is connected to a surface 3b of the light transmitting member 3. The surface 3b is the surface opposite to the surface 3a. Each of the laser medium units 2A, 2B, and 2C is connected to the light transmitting member 3 at a second surface 10b of the laser gain medium 10. The laser medium units 2A, 2B, and 2C are arranged so that the laser light L2 emitted from the laser medium unit 2A travels through the light transmitting member 3 and enters the laser medium unit 2B, and the laser light L2 emitted from the laser medium unit 2B travels through the light transmitting member 3 and enters the laser medium unit 2C. In this example, the laser medium units 2A and 2C are aligned along a second direction D2 perpendicular to the first direction D1, and the laser medium unit 2B is located between the laser medium units 2A and 2C when viewed from the first direction D1.

[0047] The laser amplifier 1 includes a laser light source unit (not shown) that outputs or guides laser light L2 toward the light transmitting member 3. The laser light L2 incident on the light transmitting member 3 first travels toward the second surface 10b of the laser gain medium 10 of the laser medium unit 2A, passes through the second layer 12, and is incident on the second surface 10b. When the laser light L2 enters the laser gain medium 10 pumped by the pumping light L1, the laser light L2 is amplified by light emitted by a stimulated emission phenomenon. The amplified laser light L2 is emitted from the second surface 10b of the laser gain medium 10 of the laser medium unit 2A. The laser light L2 emitted from the second surface 10b of the laser gain medium 10 of the laser medium unit 2A is incident on the second surface 10b of the laser gain medium 10 of the laser medium unit 2B, is amplified in the laser gain medium 10, and is emitted from the second surface 10b. In this way, in the laser amplifier 1, the laser light L2 emitted from the laser medium unit 2A (first laser medium unit) is amplified in the laser medium unit 2B (second laser medium unit).

[0048] The laser light L2 emitted from the second surface 10b of the laser gain medium 10 of the laser medium unit 2B is incident on the second surface 10b of the laser gain medium 10 of the laser medium unit 2C, is amplified in the laser gain medium 10, and is emitted from the second surface 10b. The laser light L2 emitted from the laser medium unit 2C is emitted from the light transmitting member 3 and extracted to the outside as output light of the laser amplifier device 1. Note that the laser light L2 incident on the second surface 10b of the laser gain medium 10 of each laser medium unit 2 and reaches the first surface 10a is reflected by the first layer 11 on the first surface 10a. [Action and effect]

[0049] In the laser medium unit 2, a light-guiding cooling member 20 is connected to the first surface 10a of the laser gain medium 10. The light-guiding cooling member 20 guides the pumping light L1 toward the first surface 10a and cools the laser gain medium 10. This ensures that the irradiation area of ​​the pumping light L1 and the cooling area on the first surface 10a coincide with each other, thereby ensuring a reduction in the thermal lens effect. That is, it is possible to reduce the thermal lens effect (reduce the temperature gradient) that occurs due to the difference in the amount of phase shift at the boundary between the irradiation area and the non-cooling area (see Patent Document 1). Furthermore, since the irradiation area and the cooling area can be made to coincide with each other simply by connecting the light-guiding cooling member 20 to the laser gain medium 10, it is possible to improve assembly ease compared to, for example, a case in which a cooling member is connected to the laser gain medium so that the cooling area is located within a predetermined irradiation area. Furthermore, in the laser medium unit 2, the first surface 10a of the laser gain medium 10 is composed of a first region R1 to which the light-guiding cooling member 20 is thermally connected and a second region R2 other than the first region R1, and the entire second region R2 is thermally insulated from the light-guiding cooling member 20. This makes it possible to prevent the temperature distribution in the second region R2 in a direction parallel to the first surface 10a from becoming non-uniform, and to prevent the thermal lens effect caused by the non-uniform temperature distribution in the second region R2 from occurring. Therefore, the laser medium unit 2 can improve assembly while reducing the thermal lens effect. Furthermore, in the laser medium unit 2, the light-guiding cooling member 20 connected to the first surface 10a can guide the pumping light L1 toward the first surface 10a and cool the laser gain medium 10, so that the configuration on the second surface 10b side can be simplified and the degree of freedom in arranging components can be increased.

[0050] The second region R2 surrounds the first region R1, which makes it possible to prevent the temperature distribution in the second region R2 in the direction parallel to the first surface 10a from becoming uneven, thereby further reducing the thermal lens effect.

[0051] When viewed from a first direction D1 perpendicular to the first surface 10a, the first region R1 has a shape that is line-symmetric with respect to lines LN1 and LN2 passing through the center C of the first surface 10a and point-symmetric with respect to the center C. This makes it possible to homogenize the temperature distribution in the first region R1 in the direction parallel to the first surface 10a, and further reduce the thermal lens effect.

[0052] The light-guiding cooling member 20 has a light-guiding portion 21 connected to the first surface 10a of the laser gain medium 10 and a cooling portion 22 in contact with a side surface 21c of the light-guiding portion 21. This allows the light-guiding portion 21 to guide the pumping light L1 toward the first surface 10a, and the cooling portion 22 to effectively cool the laser gain medium 10 via the light-guiding portion 21.

[0053] The light-guiding unit 21 is configured so that, when the excitation light L1 is guided by the light-guiding unit 21, the intensity distribution of the excitation light L1 in a direction parallel to the first surface 10a is homogenized. This allows the excitation light L1, whose intensity distribution in a direction parallel to the first surface 10a is homogenized, to be irradiated onto the first surface 10a, thereby further reducing the thermal lens effect. Furthermore, because the intensity distribution of the excitation light L1 can be homogenized by the light-guiding cooling member 20, the configuration can be simplified compared to, for example, a case in which a separate component (e.g., a homogenizer such as a fly's eye lens, a diffractive optical element, or a light guide) is provided to homogenize the intensity distribution of the excitation light L1. As a result, the number of parts can be reduced, the optical system can be prevented from becoming complicated, and loss of the excitation light can be suppressed.

[0054] This point will be further explained with reference to FIG. 7 . A disk-type laser head such as the laser medium unit 2 of the embodiment uses a plate-shaped laser gain medium 10. A disk-type laser head is more resistant to thermal destruction and has a smaller thermal effect than, for example, a rod-type laser head using a long laser gain medium 10, and thus may be thermally advantageous. However, the disk-type laser head is thermally advantageous when the intensity distribution of the pump light is a uniform, flat-top shape as shown in FIG. 7( a). However, when the intensity distribution of the pump light is a Gaussian shape as shown in FIG. 7( b), the disk-type laser head may have thermal characteristics similar to those of a rod-type laser head. In this regard, as described above, in the laser medium unit 2 of the embodiment, the light-guiding section 21 can homogenize the intensity distribution of the pump light L1, thereby reliably reducing the thermal lens effect. Furthermore, since the intensity distribution of the pump light L1 can be homogenized by the light-guiding cooling member 20, the configuration can be simplified compared to, for example, a case in which a separate member for homogenizing the intensity distribution of the pump light L1 is provided.

[0055] A length T1 of light-guiding section 21 in a first direction D1 perpendicular to first surface 10a is longer than a length T2 of light-guiding section 21 in a direction parallel to first surface 10a. This allows light-guiding section 21 to effectively homogenize the intensity distribution of excitation light L1.

[0056] The light source 30 is a semiconductor laser having a plurality of light-emitting regions. This can increase the intensity of the excitation light L1. On the other hand, when light from such a semiconductor laser is condensed, a light pattern for each light-emitting region remains, and the intensity distribution of the excitation light L1 tends to become Gaussian. In this regard, in the laser medium unit 2 of the embodiment, the light guiding section 21 can homogenize the intensity distribution of the excitation light L1. Therefore, even when such a semiconductor laser is used as the light source 30, the homogenized excitation light L1 can be irradiated onto the first surface 10a.

[0057] A first layer 11 that transmits the pumping light L1 but reflects the laser light L2 (emitted light) is formed on the first surface 10a. This allows the pumping light L1 to be incident on the laser gain medium 10 from the first surface 10a side, while reflecting the emitted light toward the second surface 10b side. Furthermore, when the laser light L2 is incident from the second surface 10b side, for example, it is not necessary for the laser light L2 to reach the end face 21b of the light guide 21, so there is no need to reduce the incident angle of the laser light L2 with respect to the second surface 10b. As a result, the allowable range of the incident angle of the laser light L2 with respect to the second surface 10b can be widened.

[0058] A second layer 12 that reflects the excitation light L1 while transmitting the laser light L2 (emitted light) is formed on the second surface 10b. This prevents the excitation light L1 from transmitting through the second surface 10b, while allowing the laser light L2 to be emitted from the second surface 10b.

[0059] In the laser amplifier 1, the laser light L2 is incident on the second surface 10b, and the laser light L2 is amplified by the emitted light in the laser gain medium 10 and output from the second surface 10b. In this case, the laser light L2 travels back and forth within the laser gain medium 10, so that the interaction length contributing to the amplification of the laser light L2 can be increased, and the extraction efficiency of the light energy can be improved.

[0060] In the laser amplifier 1, the plurality of laser medium units 2 include a laser medium unit 2A (first laser medium unit) and a laser medium unit 2B (second laser medium unit), and the laser light L2 emitted from the laser medium unit 2A is amplified in the laser medium unit 2B. This allows the laser light L2 to be effectively amplified by the plurality of laser medium units 2. [Variations]

[0061] In a laser medium unit 2A of a first modification shown in FIG. 8, the first layer 11 is not formed on the first surface 10a of the laser gain medium 10, but is formed on an end face 21b of the light-guiding unit 21 (the incident surface of the light-guiding cooling member 20 for the pumping light L1). The first layer 11 is formed, for example, on the entire surface of the end face 21b. The laser light L2 incident on the second surface 10b of the laser gain medium 10 is reflected by the first layer 11 on the end face 21b. In the first modification, the laser gain medium 10 and the light-guiding unit 21 are formed of different materials having similar refractive indices. For example, the laser gain medium 10 is formed of Nd-doped YAG, and the light-guiding unit 21 is formed of undoped YAG. The laser medium unit 2A of the first modification can also reduce the thermal lens effect and improve assembly ease, as in the above embodiment. Furthermore, the first layer 11 that transmits the pumping light L1 and reflects the laser light L2 (emitted light) is formed on the incident surface of the light-guiding cooling member 20 to which the pumping light L1 is incident, thereby allowing the pumping light L1 to enter the laser gain medium 10 from the first surface 10a side and reflecting the emitted light toward the second surface 10b side. Furthermore, since the first layer 11 is not formed on the first surface 10a, it is possible to easily join the laser gain medium 10 and the light-guiding cooling member 20. Note that when the laser gain medium 10 and the light-guiding section 21 are made of different materials having significantly different refractive indices, an anti-reflection layer may be formed on the first surface 10a to suppress the occurrence of loss due to reflection at the boundary between the laser gain medium 10 and the light-guiding section 21. In other words, in the first modification, the laser gain medium 10 and the light-guiding section 21 are made of different materials having similar refractive indices, so it is possible to suppress the occurrence of loss due to reflection at the boundary between the laser gain medium 10 and the light-guiding section 21.

[0062] FIG. 9 is a plan view of a laser medium unit 2 according to a second modified example. In FIG. 9, a cross section of the light-guiding cooling member 20 is shown. In a laser medium unit 2B according to the second modified example, the light-guiding cooling member 20 has a light-guiding section 21 configured as a lens barrel, and does not have a cooling section 22. The light-guiding section 21 is hollow, and the inner surface of the light-guiding section 21 is subjected to mirror polishing, metal plating, or reflective coating (coating with a dielectric multilayer film or a metal vapor deposition film). The excitation light L1 incident on the light-guiding section 21 is mixed by being guided while repeatedly reflected by the inner surface of the light-guiding section 21. That is, also in the second modified example, the light-guiding section 21 is configured so that, when the excitation light L1 is guided by the light-guiding section 21, the intensity distribution of the excitation light L1 in a direction parallel to the first surface 10a is uniform.

[0063] The light guiding unit 21 defines a flow path P therein for flowing a refrigerant 25. An inlet pipe 23 and an outlet pipe 24 are connected to the light guiding unit 21. The refrigerant 25 is introduced through the inlet pipe 23, flows through the flow path P, and is discharged to the outside through the outlet pipe 24. The refrigerant 25 is, for example, a solution or a gas. A refrigerant that does not absorb the pump light L1 is used as the refrigerant 25. The refrigerant 25 flows through the flow path P to cool the first surface 10a of the laser gain medium 10. A heat insulating member 26, for example, an O-ring, is disposed between the light guiding unit 21 and the first surface 10a. The end of the light guiding unit 21 opposite to the first surface 10a is closed by a cover member 27. The laser medium unit 2B of the second modified example can also reduce the thermal lens effect and improve assembly ease, as in the above embodiment. Furthermore, the laser gain medium 10 can be effectively cooled by flowing the refrigerant 25 through the flow path P.

[0064] A laser medium unit 2C of a third modified example shown in FIG. 10 includes multiple light sources 30. In the third modified example, the outer peripheral surface of the light guiding section 21 is formed in a tapered shape inclined with respect to the first direction D1. In this example, the outer peripheral surface of the light guiding section 21 is formed in a tapered shape inclined so that the diameter becomes smaller as it approaches the first surface 10a. The laser medium unit 2C of the third modified example can also reduce the thermal lens effect and improve assembly ease, as in the above embodiment. Furthermore, by using multiple light sources 30, the intensity of the excitation light L1 can be increased. Furthermore, because the outer peripheral surface of the light guiding section 21 is formed in a tapered shape inclined so that the diameter becomes smaller as it approaches the first surface 10a, even when multiple light sources 30 are used, the excitation light L1 can be easily incident on the light guiding section 21. Furthermore, since the outer surface of the light-guiding section 21 is formed in a tapered shape inclined with respect to the first direction D1, it is easy to repeatedly reflect the excitation light L1 on the inner surface of the light-guiding section 21, and the intensity distribution of the excitation light L1 can be effectively uniformed by the light-guiding section 21.

[0065] 11 includes a plurality of (three in this example) laser gain media 10 and a plurality of (three in this example) light-guiding cooling members 20. In the fourth modification, the laser gain media 10 and the light-guiding cooling members 20 are connected alternately.

[0066] Let us assume that the three laser gain media 10 are laser gain media 10A, 10B, and 10C, the three light-guiding cooling members 20 are light-guiding cooling members 20A, 20B, and 20C, and the light-guiding portions 21 of the light-guiding cooling members 20A, 20B, and 20C are light-guiding portions 21A, 21B, and 21C, respectively. An end face 21a of the light-guiding portion 21A is connected to a first surface 10a of the laser gain medium 10A. An end face 21b of the light-guiding portion 21B is connected to a second surface 10b of the laser gain medium 10A. An end face 21a of the light-guiding portion 21B is connected to a first surface 10a of the laser gain medium 10B. An end face 21b of the light-guiding portion 21C is connected to a second surface 10b of the laser gain medium 10B. An end face 21a of the light-guiding portion 21C is connected to a first surface 10a of the laser gain medium 10C. The second surface 10b of the laser gain medium 10C is connected to, for example, the light transmitting member 3, and serves as an input / output surface for the laser light L2.

[0067] A first layer 11 that transmits the pumping light L1 and reflects the laser light L2 is formed on the first surface 10a of the laser gain medium 10A. A layer 13 that transmits the pumping light L1 and the laser light L2 is formed on the second surfaces 10b of the laser gain media 10A and 10B and on the first surfaces 10a of the laser gain media 10B and 10C. A second layer 12 that reflects the pumping light L1 and transmits the laser light L2 is formed on the second surface 10b of the laser gain medium 10C.

[0068] The pumping light L1 is incident on the end face 21b of the light guide 21A and is absorbed successively by the laser gain media 10A, 10B, and 10C. The laser light L2 incident on the second surface 10b of the laser gain medium 10C is amplified successively by the laser gain media 10C, 10B, and 10A, and then reflected by the first layer 11 on the first surface 10a of the laser gain medium 10A. The laser light L2 travels toward the second surface 10b of the laser gain medium 10C while being amplified successively by the laser gain media 10A, 10B, and 10C, and is emitted from the second surface 10b of the laser gain medium 10C.

[0069] The laser medium unit 2D of the fourth modification can also reduce the thermal lens effect and improve assembly efficiency, as in the above embodiment. Furthermore, since the plurality of laser gain media 10 and the plurality of beam-guiding cooling members 20 are connected alternately, the pumping light L1 can be absorbed by the plurality of laser gain media 10, thereby improving the absorption efficiency of the pumping light L1. Furthermore, since the beam-guiding cooling members 20A and 20B are connected to both sides (the first surface 10a side and the second surface 10b side) of the laser gain medium 10A, the laser gain medium 10A can be pumped and cooled from both sides. Similarly, since the beam-guiding cooling members 20B and 20C are connected to both sides of the laser gain medium 10B, the laser gain medium 10B can be pumped and cooled from both sides.

[0070] A laser medium unit 2E of the fifth modified example shown in Fig. 12 includes a plurality of (two in this example) light-guiding cooling members 20. The two light-guiding cooling members 20 are light-guiding cooling members 20D and 20E, respectively, and the light-guiding sections 21 of the light-guiding cooling members 20D and 20E are light-guiding sections 21D and 21E, respectively. An end face 21a of the light-guiding section 21D is connected to a first surface 10a of the laser gain medium 10, and an end face 21b of the light-guiding section 21B is connected to a second surface 10b of the laser gain medium 10. A layer 13 that transmits the pumping light L1 and the laser light L2 is formed on the first surface 10a of the laser gain medium 10. A first layer 11 that transmits the pumping light L1 but reflects the laser light L2 is formed on the second surface 10b of the laser gain medium 10.

[0071] The laser medium unit 2E of the fifth modified example includes a plurality of (two in this example) light sources 30 and a plurality of (two in this example) condenser lenses 40. The pumping light L1 output from the first light source 30 is condensed by the first condenser lens 40, enters the end face 21b of the light guiding unit 21D, is guided by the light guiding unit 21D, and is irradiated onto the first surface 10a of the laser gain medium 10. The pumping light L1 output from the second light source 30 is condensed by the second condenser lens 40, enters the end face 21a of the light guiding unit 21E, is guided by the light guiding unit 21E, and is irradiated onto the second surface 10b of the laser gain medium 10. In this way, in this example, the pumping light L1 is irradiated from both the first surface 10a and the second surface 10b.

[0072] The laser medium unit 2E of the fifth modified example includes a dichroic mirror 5 disposed between the first focusing lens 40 and the light guiding unit 21D. The dichroic mirror 5 transmits the pumping light L1 and reflects the laser light L2. The pumping light L1 output from the first light source 30 passes through the dichroic mirror 5 and is incident on the end face 21b of the light guiding unit 21D. In this example, the laser light L2 is supplied toward the dichroic mirror 5. The laser light L2 is reflected by the dichroic mirror 5 toward the end face 21b of the light guiding unit 21D, is incident on the end face 21b of the light guiding unit 21D, is guided by the light guiding unit 21D and is incident on the first surface 10a of the laser gain medium 10. As described above, in this example, the pumping light L1 and the laser light L2 are introduced from one side of the laser gain medium 10.

[0073] The laser medium unit 2E of the fifth modified example can also reduce the thermal lens effect and improve the ease of assembly, as in the above embodiment. Furthermore, since the light-guiding cooling members 20D and 20E are connected to both sides of the laser gain medium 10, the laser gain medium 10 can be pumped and cooled from both sides, and the cooling of the laser gain medium 10 and the accumulation of energy in the laser gain medium 10 can be efficiently performed. Note that the light-guiding cooling member 20E, the second light source 30, and the second focusing lens 40 may be omitted in the fifth modified example.

[0074] As in a sixth modified example shown in FIG. 13, the laser medium unit 2 may constitute a laser oscillation device 100. The laser oscillation device 100 includes the laser medium unit 2, a partial reflection mirror (partial reflection portion) 110, and an optical member 120. The partial reflection mirror 110 is a mirror that transmits part of incident light and reflects the rest. The partial reflection mirror 110 may be a mirror having a flat surface or a mirror having a curved surface. The partial reflection mirror 110 is disposed on the optical path of the emitted light output from the laser gain medium 10, and causes the emitted light to undergo laser oscillation.

[0075] The optical element 120 is a element that functions as a Q switch and is constituted by, for example, a saturable absorber, a Pockels cell, or the like. The optical element 120 is disposed between the laser gain medium 10 and the partial reflection mirror 110. In the laser oscillation device 100, emitted light generated in the laser gain medium 10 travels back and forth between the first surface 10a (first layer 11) of the laser gain medium 10 and the partial reflection mirror 110 while being amplified, causing laser oscillation, and the laser light L2 passes through the partial reflection mirror 110 and is extracted to the outside as output light. The laser oscillation device 100 of the sixth modification can also reduce the thermal lens effect and improve assembly ease for the reasons described above. In the sixth modification, a partially reflecting layer (partial reflection portion) may be formed on the second surface 10b of the laser gain medium 10 instead of the partial reflection mirror 110. In this case, the optical element 120 is omitted. Alternatively, in the sixth modification, instead of the partial reflection mirror 110, a partial reflection layer (partial reflection portion) may be formed on the surface of the optical member 120 opposite to the laser gain medium 10 (the right side in FIG. 13).

[0076] In a seventh modified example shown in FIGS. 14 and 15 , the laser amplifier 1 includes a housing 7. In this example, the housing 7 is a vacuum chamber, and the interior of the housing 7 is in a vacuum state. That is, the housing 7 has a vacuum internal space S. The laser medium unit 2 and the light transmitting member 3 are disposed in the internal space S and housed within the housing 7. This configuration is effective in suppressing condensation on the laser gain medium 10, etc., when the laser gain medium 10 is cooled to a low temperature, for example, below 0°C. The wall of the housing 7 is provided with an entrance window 7a through which the laser light L2 enters and an exit window 7b through which the laser light L2 exits. In this example, a condenser lens 40 is attached as a window to the wall of the housing 7, and the light source 30 is disposed outside the housing 7. Alternatively, the condenser lens 40 may be disposed outside the housing 7. In this case, the wall of the housing 7 may be provided with a window that transmits the excitation light L1 from the condenser lens 40. The light transmitting member 3 and each laser gain medium 10 may be fixed to the housing 7 via a heat insulating member. In this case, it is possible to suppress the occurrence of the thermal lens effect while suppressing misalignment between the multiple laser medium units 2, thereby achieving stable operation of the laser amplifier 1. As the heat insulating member, for example, a resin member with low thermal conductivity, ceramic balls, needles, or the like may be used. When ceramic balls or needles are used, the components are supported by point contact, thereby making it possible to reduce the heat flow path and ensure sufficient insulation from the housing 7. For the reasons described above, the laser amplifier 1 of the seventh modification also reduces the thermal lens effect and improves assembly ease. The housing 7 can also be considered to be part of the laser medium unit 2.

[0077] The first region R1 and the second region R2 may be arranged on the first surface 10a of the laser gain medium 10 as in the arrangement examples shown in Figures 16(a) and 16(b). In the example of Figure 16(a), the center of the first region R1 is offset from the center C of the first surface 10a. In the example of Figure 16(b), the first region R1 is formed in a rectangular shape and is not surrounded by the second region R2. The laser medium unit 2 in which the first region R1 and the second region R2 are arranged in this manner can also reduce the thermal lens effect and improve assembly ease, as in the above embodiment.

[0078] The present invention is not limited to the above-described embodiments and modifications. The materials and shapes of the components are not limited to those described above, and various materials and shapes can be used. For example, the shape of the laser gain medium 10 as viewed from the first direction D1 is not limited to a circular shape, and may be any shape, such as a rectangular shape. The material of the cooling unit 22 is not limited to a metallic material, and may be, for example, sapphire.

[0079] In the above embodiment, the light transmitting member 3 may be omitted. For example, the light transmitting member 3 may be replaced with a space. In this case, the laser amplifier 1 can be operated in the same manner as in the above embodiment by, for example, arranging the laser medium units 2A, 2B, and 2C in the same positional relationship as in the above embodiment. In the above embodiment, the laser amplifier 1 may include only one laser medium unit 2.

[0080] The light-guiding portion 21 may have any shape, for example, a hexagonal prism. The cooling portion 22 may be omitted in the above embodiment. In this case, for example, the light-guiding portion 21 may be made of a material with high thermal conductivity (e.g., sapphire), thereby allowing the laser gain medium 10 to be cooled by natural heat dissipation. The cooling portion 22 may cool the light-guiding portion 21 by air cooling or water cooling. For example, a Peltier element may be connected to a cooling block constituting the cooling portion 22 in the above embodiment. Alternatively, a through-hole may be formed in the cooling block, and a cooling liquid or gas may be flowed through the through-hole. Such a cooling method is particularly effective when the laser gain medium 10 and the light-guiding cooling member 20 are placed in a vacuum state, as in the seventh modification, making natural heat dissipation difficult.

[0081] First layer 11 does not have to be formed over the entire surface of first surface 10a. For example, first layer 11 may be formed only on the region of first surface 10a where light-guiding section 21 is connected. However, if first layer 11 is formed over the entire surface of first surface 10a, it is possible to facilitate the task of connecting light-guiding section 21 to first surface 10a so that it is disposed on first layer 11.

[0082] In the above embodiment, a reflective layer that reflects the excitation light L1 may be formed on the entire surface of the side surface 21c of the light-guiding unit 21. The reflective layer may be, for example, a metal layer formed by plating, vapor deposition, or the like, or a reflective coating layer. When a reflective layer is formed, the excitation light L1 can be reliably reflected at the side surface 21c of the light-guiding unit 21. Furthermore, when the reflective layer is a metal plating layer, the cooling performance of the light-guiding cooling member 20 can be improved.

[0083] In the above embodiment, as in the third modification, the light guiding section 21 may be formed in a tapered shape such that the diameter decreases toward the first surface 10a of the laser gain medium 10. Alternatively, conversely, the light guiding section 21 may be formed in a tapered shape such that the diameter increases toward the first surface 10a of the laser gain medium 10. In the above embodiment, a cooling member may be connected to the second surface 10b of the laser gain medium 10. In this case, the laser gain medium 10 can be cooled from both sides, and the laser gain medium 10 can be cooled efficiently. The cooling member may be, for example, the light guiding cooling member 20. In the above embodiment, the side surface of the laser gain medium 10 may be heated. In this case, the thermal lens effect can be further reduced. [Explanation of symbols]

[0084] 1...laser amplifier, 2, 2A, 2B, 2C, 2D, 2E...laser medium unit, 10, 10A, 10B, 10C...laser gain medium, 10a...first surface, 10b...second surface, 11...first layer, 12...second layer, 20, 20A, 20B, 20C, 20D, 20E...light-guiding cooling member, 21, 21A, 21B, 21C, 21D, 21E...light-guiding section, 21c...side surface, 22...cooling section, 30...light source, 100...laser oscillator, 110...partially reflecting mirror (partially reflecting section), L1...pumping light, L2...laser light, R1...first region, R2...second region.

Claims

1. a laser gain medium formed in a plate shape, having a first surface and a second surface opposite to the first surface, and configured to generate emitted light when irradiated with excitation light from the first surface; a light-guiding cooling member connected to the first surface, guiding the pumping light toward the first surface and cooling the laser gain medium, the first surface includes a first region to which the light-guiding cooling member is thermally connected and a second region other than the first region, the second region is entirely thermally insulated from the light-guiding cooling member, The light-guiding cooling member has a light-guiding portion connected to the first surface and a cooling portion in contact with a side surface of the light-guiding portion.

2. a laser gain medium formed in a plate shape, having a first surface and a second surface opposite to the first surface, and configured to generate emitted light when irradiated with excitation light from the first surface; a light-guiding cooling member connected to the first surface, guiding the pumping light toward the first surface and cooling the laser gain medium, the first surface includes a first region to which the light-guiding cooling member is thermally connected and a second region other than the first region, the second region is entirely thermally insulated from the light-guiding cooling member, a layer that transmits the excitation light and reflects the emitted light is formed on an incident surface of the light-guiding cooling member onto which the excitation light is incident;

3. a laser gain medium formed in a plate shape, having a first surface and a second surface opposite to the first surface, and configured to generate emitted light when irradiated with excitation light from the first surface; a light-guiding cooling member connected to the first surface, guiding the pumping light toward the first surface and cooling the laser gain medium, the first surface includes a first region to which the light-guiding cooling member is thermally connected and a second region other than the first region, the second region is entirely thermally insulated from the light-guiding cooling member, The laser medium unit has a layer formed on the second surface that reflects the excitation light and transmits the emitted light.

4. a laser gain medium formed in a plate shape, having a first surface and a second surface opposite to the first surface, and configured to generate emitted light when irradiated with excitation light from the first surface; a light-guiding cooling member connected to the first surface, guiding the pumping light toward the first surface and cooling the laser gain medium, the first surface includes a first region to which the light-guiding cooling member is thermally connected and a second region other than the first region, the second region is entirely thermally insulated from the light-guiding cooling member, a plurality of the laser gain medium and a plurality of the light-guiding cooling members are provided; The laser medium unit, wherein the plurality of laser gain media and the plurality of light-guiding cooling members are connected in an alternating manner.

5. a laser gain medium formed in a plate shape, having a first surface and a second surface opposite to the first surface, and configured to generate emitted light when irradiated with excitation light from the first surface; a light-guiding cooling member connected to the first surface, for guiding the pumping light toward the first surface and for cooling the laser gain medium; a housing having a vacuum interior space; the first surface includes a first region to which the light-guiding cooling member is thermally connected and a second region other than the first region, the second region is entirely thermally insulated from the light-guiding cooling member, The laser medium unit, wherein the laser gain medium and the light-guiding cooling member are disposed in the internal space.

6. 6. The laser medium unit according to claim 1, wherein the second region surrounds the first region.

7. 7. The laser medium unit according to claim 1, wherein the first region has a shape that is line-symmetric with respect to a line passing through a center of the first surface and point-symmetric with respect to the center when viewed from a direction perpendicular to the first surface.

8. the light-guiding cooling member has a light-guiding portion connected to the first surface, 8. The laser medium unit according to claim 1, wherein the light guiding section is configured such that, when the excitation light is guided by the light guiding section, an intensity distribution of the excitation light in a direction parallel to the first surface is made uniform.

9. the light-guiding cooling member has a light-guiding portion connected to the first surface, 9. The laser medium unit according to claim 1, wherein a length of the light guiding portion in a direction perpendicular to the first surface is longer than a length of the light guiding portion in a direction parallel to the first surface.

10. a light source that outputs the excitation light; 10. The laser medium unit according to claim 1, wherein the light source is a semiconductor laser having a plurality of light-emitting regions.

11. 11. The laser medium unit according to claim 1, wherein a layer that transmits the excitation light and reflects the emitted light is formed on the first surface.

12. further comprising a plurality of light sources each outputting the excitation light; 12. The laser medium unit according to claim 1, wherein the excitation light from each of the plurality of light sources is incident on the light-guiding cooling member.

13. the light-guiding cooling member has a light-guiding portion connected to the first surface, 13. The laser medium unit according to claim 1, wherein an outer peripheral surface of the light guiding portion is formed in a tapered shape that is inclined with respect to a direction perpendicular to the first surface.

14. the light-guiding cooling member has a light-guiding portion connected to the first surface, 14. The laser medium unit according to claim 1, wherein the light guide portion is formed in a cylindrical shape and defines a flow path therein for allowing a coolant to flow.

15. A laser medium unit according to any one of claims 1 to 14, A laser amplifier device in which laser light is incident on the first surface or the second surface, and the laser light is amplified by the emitted light in the laser gain medium and output.

16. A laser amplifier device comprising a laser medium unit, The laser medium unit comprises: a laser gain medium formed in a plate shape, having a first surface and a second surface opposite to the first surface, and configured to generate emitted light when irradiated with excitation light from the first surface; a light-guiding cooling member connected to the first surface, guiding the pumping light toward the first surface and cooling the laser gain medium, the first surface includes a first region to which the light-guiding cooling member is thermally connected and a second region other than the first region, the second region is entirely thermally insulated from the light-guiding cooling member, A laser amplifier device in which laser light is incident on the second surface, and the laser light amplified by the emitted light in the laser gain medium is output from the second surface.

17. A laser amplifier device comprising a plurality of laser medium units, Each of the plurality of laser medium units comprises: a laser gain medium formed in a plate shape, having a first surface and a second surface opposite to the first surface, and configured to generate emitted light when irradiated with excitation light from the first surface; a light-guiding cooling member connected to the first surface, guiding the pumping light toward the first surface and cooling the laser gain medium, the first surface includes a first region to which the light-guiding cooling member is thermally connected and a second region other than the first region, the second region is entirely thermally insulated from the light-guiding cooling member, In each of the plurality of laser medium units, laser light is incident on the second surface, and the laser light amplified by the emitted light in the laser gain medium is emitted from the second surface; the plurality of laser medium units include a first laser medium unit and a second laser medium unit; The laser amplifier, wherein the laser light emitted from the first laser medium unit is amplified in the second laser medium unit.

18. A laser medium unit according to any one of claims 1 to 14, a partial reflector disposed on an optical path of the emitted light output from the laser gain medium, the partial reflector causing the emitted light to undergo laser oscillation.

Images