Laser elements and electronic devices

Abstract

[Problem] To prevent a decrease in oscillation efficiency of laser beams and a decrease in conversion efficiency of light wavelengths due to thermal interference. [Solution] A laser element according to the present invention is provided with: a laminated semiconductor layer having a first reflection layer for a first wavelength and an active layer for performing surface emission of light having the first wavelength; a laser medium that is disposed at a rear side of the laminated semiconductor layer on the optical axis thereof and that has a second reflection layer for a second wavelength on a first surface facing the laminated semiconductor layer and a third reflection layer for the first wavelength on a second surface on the reverse side of the first surface; a fourth reflection layer for the second wavelength, said fourth reflection layer being disposed on the second surface or at a side farther back than the second surface on the optical axis; a first resonator for resonating light having the first wavelength between the first reflection layer and the third reflection layer; a second resonator for resonating light having the second wavelength between the second reflection layer and the fourth reflection layer; and a heat dissipating section that is disposed between the laminated semiconductor layer and the laser medium and that dissipates heat generated in at least one of the laminated semiconductor layer and the laser medium.

Description

[Technical Field]

[0001] The present disclosure relates to laser devices and electronic devices. [Background technology]

[0002] The peak power of a laser is defined as pulse energy divided by pulse width, and to obtain higher peak power, it is important to obtain a shorter pulse width. A Q-switched solid-state laser that outputs laser pulses has the characteristic that the length of its own resonator is proportional to the obtained pulse width, and the minimum resonator length is determined by the length of the solid-state laser medium used. The length of the solid-state laser medium installed in the resonator as a gain medium is determined by the amount of pump light absorbed, so simply shortening the length of the solid-state laser medium will result in insufficient absorption of the pump light and a significant decrease in pumping efficiency.

[0003] For this reason, in the conventional method of externally pumping a Q-switched solid-state laser medium with a semiconductor laser, it is not desirable to shorten the length of the solid-state laser medium beyond the pump light absorption length, and it is not possible to obtain shorter pulses. In other words, shortening the length of the solid-state laser medium in an attempt to obtain a short pulse width reduces the amount of pump light absorbed and decreases the pumping efficiency. Conversely, extending the length of the solid-state laser medium in an attempt to increase the amount of pump light absorbed increases the resonator length, resulting in a trade-off that increases the pulse width.

[0004] On the other hand, from the perspective of manufacturing and light source output stability, conventional Q-switched solid-state lasers require highly accurate positioning of multiple optical elements and assembly and adjustment, making them unsuitable for mass production and making it difficult to reduce costs. In addition, there are issues with the stability of the light source output due to misalignment of each optical element.

[0005] Conventionally, a method has been known in which a Q-switched solid-state laser is externally excited using, for example, a semiconductor laser to generate a short-pulse laser (see Patent Documents 1 and 2). Since the obtained pulse width is proportional to the cavity length of the Q-switched solid-state laser, it is desirable to shorten the cavity length and obtain a shorter pulse width in order to obtain a higher laser peak power.

[0006] However, with conventional methods, the thickness of the solid-state laser medium that can be used is limited by the absorption length, which is determined by the wavelength of the pumping semiconductor laser and the absorption coefficient of the solid-state laser medium at that wavelength. For example, in the case of Nd:YAG (10 at%), which is the most commonly used material in Q-switched solid-state lasers, the absorption length for 808 nm pumping light is about 10 mm. If the length of the solid-state laser medium is made shorter than this length, the remaining pumping light that is not absorbed returns to the semiconductor laser, causing unstable operation or generating heat. For disk lasers, a method has been proposed in which the pumping light is folded back multiple times, but this requires a complex pumping optical system, posing challenges to miniaturization and cost reduction.

[0007] Furthermore, in the past, in order to miniaturize laser light sources, a method has been proposed in which a vertical cavity surface emitting laser (VCSEL) for excitation and a solid-state laser medium are laminated together, as shown in Patent Document 3. However, there is only a description that they are "laminated together," and there is no specific description as to whether the light transmitting surfaces are bonded together, what bonding process is used, or how the problems that arise as a result are solved. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-219232 [Patent Document 2] Japanese Patent Application Publication No. 2019-176119 [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-173393 Summary of the Invention [Problem to be solved by the invention]

[0009] When a surface-emitting laser and a solid-state laser medium are integrated to reduce the size, thermal interference may occur between them, which can result in a decrease in the laser light oscillation efficiency of the surface-emitting laser and a decrease in the optical wavelength conversion efficiency of the solid-state laser medium.

[0010] Therefore, the present disclosure provides a laser element and electronic device that can prevent a decrease in the oscillation efficiency of laser light and a decrease in the conversion efficiency of light wavelength due to thermal interference. [Means for solving the problem]

[0011] In order to solve the above problems, according to the present disclosure, there is provided a light emitting device including: a laminated semiconductor layer having a first reflective layer for a first wavelength and an active layer that performs surface emission of the first wavelength; a laser medium disposed on the rear side of the optical axis of the laminated semiconductor layer, the laser medium having a second reflective layer for a second wavelength on a first surface facing the laminated semiconductor layer and a third reflective layer for the first wavelength on a second surface opposite to the first surface; a fourth reflective layer for the second wavelength, which is disposed on the second surface or on a rear side of the second surface along the optical axis; a first resonator that resonates light of the first wavelength between the first reflective layer and the third reflective layer; a second resonator that resonates light of the second wavelength between the second reflective layer and the fourth reflective layer; a heat dissipation unit disposed between the laminated semiconductor layer and the laser medium, for dissipating heat generated by at least one of the laminated semiconductor layer and the laser medium; A laser element is provided in which the optical axis of the laminated semiconductor layers and the optical axis of the laser medium are arranged on the same axis.

[0012] The heat dissipation section may be disposed between the laminated semiconductor layer and the laser medium and may include a first member having a higher thermal conductivity than the laser medium.

[0013] The laser medium may include a metal layer disposed on a part or all of the surface of the first member facing the laser medium, the metal layer having a thermal conductivity higher than that of the laminated semiconductor layer and the laser medium.

[0014] The laser device may further include a second member bonded to the side surfaces of the laminated semiconductor layer, the first member, and the laser medium, and configured to dissipate heat transferred to the first member.

[0015] a substrate supporting the laminated semiconductor layer; a bonding wire connected to a pad on the substrate and an electrode of the laminated semiconductor layer; The second member may be disposed so as to cover the side surfaces of the laminated semiconductor layer and the laser medium, and the bonding wire.

[0016] the first member includes at least one of sapphire and diamond, The second member may include a metallic material.

[0017] The optical fiber may further include a protective layer disposed on a surface of the first member facing the laminated semiconductor layer, the protective layer transmitting light of the first wavelength and reflecting light of the second wavelength.

[0018] The first member may have a first region that transmits light of the first wavelength, and a second region that is disposed around the first region and has a higher thermal conductivity than the laser medium.

[0019] The second region may be an insulating material or a metallic material.

[0020] the second region is disposed so as to surround the first region, The outer peripheral surface of the second region or a corner of the outer peripheral surface may be positioned equidistant from the center position of the first region.

[0021] A plurality of the first resonators and a plurality of the second resonators may be provided in a planar direction of the laminated semiconductor layer, the heat dissipation portion, and the laser medium.

[0022] The heat dissipation section may have an air gap disposed between the laminated semiconductor layer and the laser medium.

[0023] The light source may further include a first optical element disposed between the second reflective layer to the fourth reflective layer, and configured to expand the beam diameter of the light of the second wavelength.

[0024] The first resonator may include a second optical element that focuses the light of the first wavelength in an optical axis direction.

[0025] a saturable absorber having the fourth reflecting layer on a third surface opposite to the laser medium, The optical axis of the laminated semiconductor layer, the optical axis of the laser medium, and the optical axis of the saturable absorber may be arranged on the same axis.

[0026] The laminated semiconductor layer, the laser medium, and the saturable absorber may be integrally bonded together.

[0027] The optical fiber may further include a polarization control element that is disposed between the laser medium and the saturable absorber or on the rear side of the saturable absorber along the optical axis, and that controls the polarization state of the light of the second wavelength.

[0028] The fourth reflective layer may be an output coupling mirror in the second cavity.

[0029] the laminated semiconductor layer has a fifth reflective layer for the first wavelength, the fifth reflective layer being disposed closer to the laser medium than the first reflective layer; The fifth reflective layer may transmit a portion of the light of the first wavelength.

[0030] According to the present disclosure, a laser element; a control unit that controls the emission of light from the laser element, The laser element is a laminated semiconductor layer having a first reflective layer for a first wavelength and an active layer for surface emitting light of the first wavelength; a laser medium disposed on the rear side of the optical axis of the laminated semiconductor layer, the laser medium having a second reflective layer for a second wavelength on a first surface facing the laminated semiconductor layer and a third reflective layer for the first wavelength on a second surface opposite to the first surface; a fourth reflective layer for the second wavelength, which is disposed on the second surface or on a rear side of the second surface along the optical axis; a first resonator that resonates light of the first wavelength between the first reflective layer and the third reflective layer; a second resonator that resonates light of the second wavelength between the second reflective layer and the fourth reflective layer; a heat dissipation unit disposed between the laminated semiconductor layer and the laser medium, for dissipating heat generated by at least one of the laminated semiconductor layer and the laser medium; An electronic device is provided, in which the optical axis of the laminated semiconductor layer and the optical axis of the laser medium are arranged on the same axis. [Brief explanation of the drawings]

[0031] [Figure 1] 1 is a diagram showing the basic configuration of a laser element according to the present disclosure. [Figure 2] FIG. 1 is a schematic cross-sectional view of a laser element equipped with a heat dissipation portion according to a first embodiment. [Figure 3] FIG. 10 is a schematic cross-sectional view of a laser element equipped with a heat dissipation portion according to a second embodiment. [Figure 4] FIG. 10 is a schematic cross-sectional view of a laser element equipped with a heat dissipation portion according to a third embodiment. [Figure 5] FIG. 10 is a schematic cross-sectional view of a laser element equipped with a heat dissipation portion according to a fourth embodiment. [Figure 6] FIG. 10 is a schematic cross-sectional view of a laser element equipped with a heat dissipation portion according to a fifth embodiment. [Figure 7] FIG. 13 is a schematic cross-sectional view of a laser element equipped with a heat dissipation part according to a sixth embodiment. [Figure 8] FIG. 13 is a schematic cross-sectional view of a laser element equipped with a heat dissipation part according to a seventh embodiment. [Figure 9] FIG. 13 is a schematic cross-sectional view of a laser element equipped with a heat dissipation part according to an eighth embodiment. [Figure 10]FIG. 13 is a schematic cross-sectional view of a laser element equipped with a heat dissipation part according to a ninth embodiment. [Figure 11A] FIG. 22 is a diagram schematically showing an example of a planar shape of a heat discharging portion according to a tenth embodiment. [Figure 11B] FIG. 22 is a diagram schematically showing another example of the planar shape of the heat discharging portion according to the tenth embodiment. [Figure 11C] FIG. 22 is a diagram schematically showing another example of the planar shape of the heat discharging portion according to the tenth embodiment. [Figure 11D] FIG. 22 is a diagram schematically showing another example of the planar shape of the heat discharging portion according to the tenth embodiment. [Figure 12] FIG. 1 is a schematic cross-sectional view of a laser array in which a plurality of lens elements are arranged in a one-dimensional or two-dimensional direction. [Figure 13A] FIG. 10 is a diagram showing the temperature distribution of a laser light source at the center of a laser array that does not have a heat dissipation section. [Figure 13B] FIG. 10 is a diagram showing the temperature distribution of a laser light source at the center of a laser array equipped with a heat dissipation section. [Figure 13C] FIG. 10 is a diagram showing the temperature distribution of laser light sources at the corners of a laser array that does not have a heat dissipation section. [Figure 13D] 10A and 10B are diagrams showing the temperature distribution of laser light sources at the corners of a laser array equipped with a heat dissipation section; [Figure 14] 3A to 3C are diagrams schematically illustrating a manufacturing process for a laser element according to the present disclosure. [Figure 15] FIG. 1 is a diagram showing a laser element in which a first transparent medium is disposed between an excitation light source and a solid-state laser medium. [Figure 16] FIG. 1 is a diagram showing the basic configuration of a laser element that does not have a saturable absorber. [Figure 17A] A perspective view showing the configuration of Innoslab. [Figure 17B] FIG. 17B is a plan view seen from the Y direction of FIG. 17A. [Figure 17C] FIG. 17B is a plan view seen from the Z direction of FIG. 17A. [Figure 18A] 1 is a cross-sectional view of a laser gain element according to the present disclosure; [Figure 18B] 1 is a perspective view of a laser gain element according to the present disclosure; [Figure 18C] FIG. 2 is a plan view schematically showing the optical path of laser light within the laser amplifier element. [Figure 19A] 18B is a cross-sectional view of the laser amplification element in which the heat dissipation performance of the first heat dissipation member in FIG. 18A is improved. [Figure 19B] A cross-sectional view taken along line AA in Figure 19A. [Figure 20] FIG. 1 is a diagram showing an example of a schematic configuration of an endoscope system. [Figure 21] FIG. 21 is a block diagram showing an example of the functional configuration of the camera and the CCU shown in FIG. 20. [Figure 22] FIG. 1 is a diagram showing an example of a schematic configuration of a microsurgery system. DETAILED DESCRIPTION OF THE INVENTION

[0032] Hereinafter, an embodiment of a laser device will be described with reference to the drawings. The following description will focus on the main components of the laser device, but the laser device may include components and functions that are not shown or described. The following description does not exclude components and functions that are not shown or described.

[0033] (Technical features of the laser element according to the present disclosure) First, before describing the internal configuration and operation of the laser element according to the present disclosure, the technical features of the laser element according to the present disclosure will be described.

[0034] The laser element according to the present disclosure has a structure in which a part of a surface-emitting laser is used as an excitation light source and a solid-state laser medium for Q-switching are integrally joined together. As will be described later, the laser element according to the present disclosure may include a laser element that does not have a Q-switching function, but first, a laser element that has a Q-switching function will be described.

[0035] In the laser device according to the present disclosure, a solid-state laser medium for Q-switching is shared by two resonators, each of which has a first resonator that resonates at a first wavelength and a second resonator that resonates at a second wavelength (also called a Q-switched solid-state laser resonator).

[0036] By sharing the solid-state laser medium between the two resonators, high-intensity excitation of the solid-state laser medium within the first resonator is possible, even if the length of the solid-state laser medium is shortened, and laser pulses with shorter pulse widths can be generated.

[0037] Furthermore, the laser element according to the present disclosure is an integrated laminated structure that can be fabricated using semiconductor process technology, and therefore has excellent mass productivity and stability of laser output.

[0038] Here, the excitation light source is a form of a vertical cavity surface emitting laser (VCSEL). It differs from a VCSEL in that at least one of the mirrors constituting the resonator is provided outside the laminated semiconductor layer, which is the main body of the excitation light source. As will be described later, the laser element according to the present disclosure has a structure in which a solid-state laser medium is disposed between the laminated semiconductor layer and a mirror disposed outside the laminated semiconductor layer.

[0039] As described above, the laser element according to the present disclosure can generate laser pulses with a short pulse width by Q-switching, but heat generated by the non-conversion of light from the excitation light source is transferred to the solid-state laser medium, which may cause an increase in the temperature of the solid-state laser medium. If the temperature of the solid-state laser medium increases, the efficiency of conversion of the optical wavelength from the first wavelength to the second wavelength in the solid-state laser medium decreases. The greater the optical output intensity of the excitation light source, the greater the effect of the decrease in the efficiency of conversion of the optical wavelength in the solid-state laser medium.

[0040] In addition to the heat generated by the pump light source, heat generated by the solid-state laser medium may be transferred to the pump light source, further increasing the temperature of the pump light source. If the temperature of the pump light source increases, the IL characteristics (light emission efficiency) of the pump light source will deteriorate. Furthermore, if the temperature of the pump light source increases, the temperature of the active layer (junction temperature Tj) of the pump light source will increase, deteriorating long-term reliability (MTTF: Mean Time To Failure).

[0041] To solve the above-mentioned problems, the laser device according to the present disclosure has the following three features. (1) The first and second resonators share a solid-state laser medium. The first resonator includes a pumping light source and a solid-state laser medium. The second resonator includes a solid-state laser medium and a saturable absorber, and performs Q-switched laser oscillation using the pumping light from the first resonator.

[0042] (2) A heat exhaust unit is provided between the pumping light source and the solid-state laser medium. The heat exhaust unit exhausts heat generated by at least one of the pumping light source and the solid-state laser medium.

[0043] (3) The pumping light source, the solid-state laser medium, and the saturable absorber have an integrated structure. In the laser device according to the present disclosure, excitation light generated by injecting current into an excitation light source is absorbed by a solid-state laser medium in a first resonator. The solid-state laser medium, together with a saturable absorber installed adjacent to the first resonator, constitutes a second resonator. When the solid-state laser medium is sufficiently excited and the output of spontaneously emitted light increases and exceeds a certain threshold, the optical absorption rate in the saturable absorber drops sharply, allowing the spontaneously emitted light generated in the solid-state laser medium to pass through the saturable absorber, causing stimulated emission in the solid-state laser medium. This results in Q-switched pulse oscillation.

[0044] (Basic structure of laser element) Specific embodiments of the laser device according to the present disclosure will be described below. Fig. 1 is a diagram showing the basic configuration of a laser device 1 according to the present disclosure. The laser device 1 in Fig. 1 has a configuration in which an excitation light source 2, a solid-state laser medium 3, and a saturable absorber 4 are integrally bonded together.

[0045] The pumping light source 2 is a partial structure of the above-mentioned VCSEL and has a laminated semiconductor layer structure. Hereinafter, the pumping light source 2 may also be referred to as the laminated semiconductor layer 2. The pumping light source 2 in FIG. 1 has a structure in which a substrate 5, an n-contact layer 33, a fifth reflective layer R5, a cladding layer 6, an active layer 7, a cladding layer 8, a pre-oxidation layer 31, and a first reflective layer R1 are laminated in this order. Note that although the laser device 1 in FIG. 1 shows a bottom-emission type configuration in which continuous wave (CW) pumping light is emitted from the substrate 5, it may also have a top-emission type configuration in which CW pumping light is emitted from the first reflective layer R1 side.

[0046] The substrate 5 is, for example, an n-GaAs substrate 5. The n-GaAs substrate 5 is desirably as thin as possible because it absorbs a certain proportion of the light of the first wavelength λ1, which is the excitation wavelength of the excitation light source 2. On the other hand, it is desirably thick enough to maintain mechanical strength during the bonding process described below.

[0047] The active layer 7 emits light of the first wavelength λ1. The cladding layers 6 and 8 are, for example, AlGaAs cladding layers. The first reflective layer R1 reflects light of the first wavelength λ1. The fifth reflective layer R5 has a certain transmittance for light of the first wavelength λ1. The first reflective layer R1 and the fifth reflective layer R5 are, for example, electrically conductive semiconductor distributed Bragg reflectors (DBRs). Current is injected from the outside through the first reflective layer R1 and the fifth reflective layer R5, causing recombination and light emission in the quantum wells in the active layer 7, resulting in laser oscillation of the first wavelength λ1. A portion of the pre-oxidation layer (for example, an AlAs layer) 31 on the cladding layer side of the first reflective layer R1 is oxidized to become a post-oxidation layer (for example, an Al2O3 layer) 32.

[0048] The fifth reflective layer R5 is disposed on, for example, an n-GaAs substrate 5. For example, the fifth reflective layer R5 is made of Al doped with an n-type dopant (for example, silicon). z1 Ga 1-z1 As / Al z2 Ga 1-z2The fifth reflective layer R5 has a multilayer reflective film made of As (0≦z1≦z2≦1). The fifth reflective layer R5 is also called an n-DBR. More specifically, an n-contact layer 33 is disposed between the fifth reflective layer R5 and the n-GaAs substrate 5.

[0049] The active layer 7 is made of, for example, Al x1 In y1 Ga 1-x1-y1 As layer and Al x3 In y3 Ga 1-x3-y3 It has a multi-quantum well layer with an As layer stacked thereon.

[0050] The first reflective layer R1 has a multi-reflection film made of, for example, Alz3Ga1-z3As / AlZ4Ga1-z4As (0≦z3≦z4≦1) doped with a p-type dopant (e.g., carbon). The first reflective layer R1 is also called a p-DBR.

[0051] The semiconductor layers R5, 6, 7, 8, and R1 in the excitation light source 2 can be formed using a crystal growth method such as MOCVD (metal organic chemical vapor deposition) or MBE (molecular beam epitaxy). After the crystal growth, processes such as mesa etching for element isolation, formation of an insulating film, and deposition of an electrode film are performed, enabling the device to be driven by current injection.

[0052] The solid-state laser medium 3 is bonded to the end face of the n-GaAs substrate 5 of the pumping light source 2 opposite to the fifth reflecting layer R5. Hereinafter, the end face of the solid-state laser medium 3 facing the pumping light source 2 will be referred to as the first face F1, and the end face of the solid-state laser medium 3 facing the saturable absorber 4 will be referred to as the second face F2. The laser pulse output face of the saturable absorber 4 will be referred to as the third face F3, and the end face of the pumping light source 2 facing the solid-state laser medium 3 will be referred to as the fourth face F4. The end face of the saturable absorber 4 facing the solid-state laser medium 3 will be referred to as the fifth face F5. Although shown separately in FIG. 1 for convenience, the fourth face F4 of the pumping light source 2 is bonded to the first face F1 of the solid-state laser medium 3, and the second face F2 of the solid-state laser medium 3 is bonded to the fifth face F5 of the saturable absorber 4.

[0053] 1 includes a first resonator 11 and a second resonator 12. The first resonator 11 resonates light of a first wavelength λ1 between a first reflective layer R1 in the pumping light source 2 and a third reflective layer R3 in the solid-state laser medium 3. The second resonator 12 resonates light of a second wavelength λ2 between a second reflective layer R2 in the solid-state laser medium 3 and a fourth reflective layer R4 in the saturable absorber 4.

[0054] The second resonator 12 is also called a Q-switched solid-state laser resonator 12. A third reflective layer R3, which is a highly reflective layer, is provided in the solid-state laser medium 3 so that the first resonator 11 can perform stable resonant operation. In a typical pumping light source 2, a partial reflecting mirror for emitting light of the first wavelength λ1 to the outside is disposed at the position of the third reflective layer R3 in FIG. 1. In contrast, in the laser device 1 in FIG. 1, the third reflective layer R3 is used to confine the power of the pumping light of the first wavelength λ1 within the first resonator 11, and therefore the third reflective layer R3 is made to be a highly reflective layer.

[0055] In this way, three reflective layers (the first reflective layer R1, the fifth reflective layer R5, and the third reflective layer R3) are provided inside the first resonator 11, which is composed of the pumping light source 2 and the solid-state laser medium 3. Therefore, the first resonator 11 has a coupled cavity structure.

[0056] The solid-state laser medium 3 is excited by confining the power of the pump light of the first wavelength λ1 within the first resonator 11. This generates Q-switched laser pulse oscillation in the second resonator 12. The second resonator 12 resonates the light of the second wavelength λ2 between the second reflective layer R2 in the solid-state laser medium 3 and the fourth reflective layer R4 in the saturable absorber 4. The second reflective layer R2 is a highly reflective layer, while the fourth reflective layer R4 is a partially reflective layer. In FIG. 1, the fourth reflective layer R4 is provided on the end face of the saturable absorber 4, but it may also be located behind the saturable absorber 4 along the optical axis. "Behind the optical axis" refers to the direction in which light is emitted on the optical axis. In other words, the fourth reflective layer R4 does not necessarily have to be located inside or on the surface of the saturable absorber 4. The fourth reflective layer R4 is an output coupling mirror in the second resonator 12.

[0057] The solid-state laser medium 3 includes, for example, a Yb:YAG (yttrium aluminum garnet) crystal doped with Yb (ytterbium). In this case, the first wavelength λ1 of the first resonator 11 is 940 nm, and the second wavelength λ2 of the second resonator 12 is 1030 nm.

[0058] The solid-state laser medium 3 is not limited to Yb:YAG, and for example, at least one of Nd:YAG, Nd:YVO4, Nd:YLF, Nd:glass, Yb:YAG, Yb:YLF, Yb:FAP, Yb:SFAP, Yb:YVO, Yb:glass, Yb:KYW, Yb:BCBF, Yb:YCOB, Yb:GdCOB, and YB:YAB can be used as the solid-state laser medium 3. The form is not limited to crystal, and ceramic materials can also be used.

[0059] Furthermore, the solid-state laser medium 3 may be a four-level solid-state laser medium 3 or a quasi-three-level solid-state laser medium 3. However, since the appropriate pumping wavelength (first wavelength λ1) differs depending on the crystal, it is necessary to select the semiconductor material of the active layer 7 in the pumping light source 2 according to the material of the solid-state laser medium 3.

[0060] The saturable absorber 4 includes, for example, a YAG (Cr:YAG) crystal doped with Cr (chromium). The saturable absorber 4 is a material whose transmittance increases when the intensity of incident light exceeds a predetermined threshold. The transmittance of the saturable absorber 4 increases due to the excitation light of the first wavelength λ1 from the first resonator 11, and a laser pulse of the second wavelength λ2 is emitted. This is called a Q-switch. V:YAG can also be used as the material for the saturable absorber 4. However, other types of saturable absorbers 4 may also be used. Furthermore, this does not preclude the use of an active Q-switch element as the Q-switch.

[0061] 1, the pump light source 2, the solid-state laser medium 3, and the saturable absorber 4 are shown separately, but they are actually bonded together using a bonding process to form an integrated laminated structure. Examples of bonding processes that can be used include surface activated bonding, atomic diffusion bonding, and plasma activated bonding. Alternatively, other bonding (adhesion) processes can be used.

[0062] To stably bond the solid-state laser medium 3 to the pumping light source 2, the surface of the n-GaAs substrate 5 within the pumping light source 2 must be flat. Therefore, as described above, it is desirable to arrange the electrodes E1 and E2, which are used to inject current into the first reflective layer R1 and the fifth reflective layer R5, so that they are not exposed on the surface of the n-GaAs substrate 5. In the example shown in FIG. 1 , electrodes E1 and E2 are arranged on the end face of the pumping light source 2 facing the first reflective layer R1. Electrode E1 is a p-electrode and is electrically connected to the first reflective layer R1. Electrode E2 is an n-electrode formed by filling the inner wall of a trench extending from the first reflective layer R1 to the n-contact layer 33 with a conductive material 35 via an insulating film 34. By arranging electrodes E1 and E2 on the same end face of the pumping light source 2 as shown in FIG. 1 , this end face can be solder-mounted to a support substrate (not shown). Even when multiple laser elements are arranged in an array, arranging electrodes E1 and E2 on the same end face allows this end face to be mounted on a support substrate. The shapes and locations of the electrodes E1 and E2 shown in FIG. 1 are merely examples.

[0063] In this way, by forming the laser element 1 of Figure 1 into a stacked structure, it becomes easy to produce the stacked structure and then dic it into individual chips, or to form a laser array in which multiple laser elements 1 are arranged in an array on a single substrate.

[0064] When fabricating a laser device 1 with a laminated structure using a bonding process, the arithmetic mean roughness Ra of each surface layer must be approximately 1 nm or less, preferably 0.5 nm or less. Chemical mechanical polishing (CMP) is used to achieve these arithmetic mean roughnesses. To avoid optical loss at the interfaces between layers, a dielectric multilayer film may be interposed between the layers and bonded via the dielectric multilayer film. For example, the refractive index n of the GaAs substrate 5, which serves as the base substrate for the pumping light source 2, at a wavelength of 940 nm is 3.2, which is higher than that of YAG (n: 1.7) and other common dielectric multilayer film materials. Therefore, when bonding the solid-state laser medium 3 and saturable absorber 4 to the pumping light source 2, it is necessary to prevent optical loss due to refractive index mismatch. Specifically, it is desirable to place an anti-reflection film (AR coating or anti-reflection coating) between the pumping light source 2 and the solid-state laser medium 3 to prevent reflection of the light of the first wavelength λ1 of the first resonator 11. It is also desirable to place an anti-reflection film (AR coating film or anti-reflection coating film) between the solid-state laser medium 3 and the saturable absorber 4 .

[0065] Depending on the bonding material, polishing may be difficult. For example, a material transparent to the first wavelength λ1 and the second wavelength λ2, such as SiO2, may be deposited as a base layer for bonding, and this SiO2 layer may be polished to an arithmetic mean roughness Ra of approximately 1 nm (preferably 0.5 nm or less) to be used as the interface for bonding. Here, materials other than SiO2 may also be used as the base layer, and the material is not limited here. An anti-reflective film may be provided between the SiO2 base layer material and the substrate layer.

[0066] Dielectric multilayer films include short-wavelength transmission filter films (SWPF), long-wavelength transmission filter films (LWPF), band-pass filter films (BPF), and anti-reflection protective films (AR). They are coating layers consisting of alternating layers of high-refractive index material and low-refractive index material. It is desirable to use different types of dielectric multilayer films as needed. The dielectric multilayer film can be formed by physical vapor deposition (PVD), specifically, vacuum deposition, ion-assisted deposition, sputtering, or other deposition methods. The film formation method is not critical. The properties of the dielectric multilayer film can also be selected arbitrarily. For example, the second reflective layer R2 can be a short-wavelength transmission filter film, and the third reflective layer R3 can be a long-wavelength transmission filter film. Furthermore, applying a long-wavelength transmission filter film to the third reflective layer R3 can prevent the first wavelength from penetrating the saturable absorber and thus prevent malfunction of the Q-switch. Note that short wavelength transmission means transmitting light of the first wavelength λ1 and reflecting light of the second wavelength λ2, while long wavelength transmission means reflecting light of the first wavelength λ1 and transmitting light of the second wavelength λ2.

[0067] A polarizer with a photonic crystal structure that separates the ratio of P-polarized light and S-polarized light may be provided inside the second resonator 12. A diffraction grating may be provided inside the second resonator 12 to convert the polarization state of the emitted laser pulse from random polarization to linear polarization. The fine grooves of the photonic crystal structure or diffraction grating can be used as an interface for bonding by forming a film of a material such as SiO2 and polishing it.

[0068] (Operating principle of laser element 1) Next, the operation of the laser device 1 in Fig. 1 will be described. By injecting a current into the active layer 7 via the electrodes of the pumping light source 2, laser oscillation of the first wavelength λ1 occurs in the first resonator 11, exciting the solid-state laser medium 3. Because the saturable absorber 4 is bonded to the solid-state laser medium 3, in the initial stage of laser oscillation of the first wavelength λ1, the spontaneously emitted light from the solid-state laser medium 3 is absorbed by the saturable absorber 4, and optical feedback by the fourth reflecting layer R4 on the emission surface side of the saturable absorber 4 does not occur, preventing Q-switched laser oscillation.

[0069] Thereafter, the power of the pumping light of the first wavelength λ1 accumulates in the solid-state laser medium 3, and when the solid-state laser medium 3 reaches a sufficiently pumped state, the output of the spontaneously emitted light increases, and when it exceeds a certain threshold, the light absorption rate in the saturable absorber 4 drops sharply, allowing the spontaneously emitted light generated in the solid-state laser medium 3 to pass through the saturable absorber 4. As a result, the light of the first wavelength λ1 is emitted from the solid-state laser medium 3 by the first resonator 11, and the second resonator 12 resonates the light of the second wavelength λ2 between the second reflective layer R2 and the fourth reflective layer R4. This causes Q-switched laser oscillation, and a Q-switched laser pulse is emitted via the fourth reflective layer R4 toward space (the space on the right in FIG. 1).

[0070] A nonlinear optical crystal for wavelength conversion can be placed inside the second resonator 12. The wavelength of the laser pulse after wavelength conversion can be changed depending on the type of nonlinear optical crystal. Examples of wavelength conversion materials include nonlinear optical crystals such as LiNbO3, BBO, LBO, CLBO, BiBO, KTP, and SLT. Phase matching materials similar to these may also be used as the wavelength conversion material. However, the type of wavelength conversion material is not critical. The second wavelength λ2 can be converted to another wavelength by the wavelength conversion material.

[0071] The above describes the basic configuration and operating principle for obtaining Q-switched laser oscillation according to the present disclosure. However, the above basic configuration cannot prevent a decrease in the oscillation efficiency of laser light due to thermal interference between the excitation light source and the solid-state laser medium, or a decrease in the conversion efficiency of light wavelength.

[0072] (Causes and solutions for thermal interference) When the pumping light source 2 and the solid-state laser medium 3, which are made of laminated semiconductor layers, are adjacent to each other or directly bonded, the temperature of the pumping light source rises as the current flowing through the active layer 7 of the pumping light source 2 increases, and heat is transferred from the pumping light source 2 to the solid-state laser medium 3, causing the temperature of the solid-state laser medium 3 to rise. This reduces the efficiency of conversion of the optical wavelength from the first wavelength to the second wavelength in the solid-state laser medium 3. On the other hand, when the temperature of the solid-state laser medium 3 rises due to pumping light absorption, heat is transferred from the solid-state laser medium 3 to the pumping light source 2, causing the temperature of the pumping light source 2 to rise further. This causes thermal interference between the pumping light source 2 and the solid-state laser medium 3, deteriorating the IL characteristics (light emission efficiency) of the pumping light source 2 and increasing the junction temperature Tj of the active layer 7, resulting in a deterioration in long-term reliability (MTTF: Mean Time To Failure).

[0073] To suppress thermal interference between the pumping light source 2 and the solid-state laser medium 3, it is desirable to provide a heat dissipation section between them. The heat dissipation section is, for example, a transparent material that can transmit light of the first wavelength and has a higher thermal conductivity than the solid-state laser medium 3. Generally, YAG, which has a thermal conductivity of 17 W / (m·K), is often used as the material for the solid-state laser medium 3. In particular, when the substrate size in the direction perpendicular to the optical axis of the solid-state laser medium 3 is significantly larger (e.g., several mm) than the beam diameter (100 μm), the temperature gradient within the surface of the solid-state laser medium 3 becomes large. Therefore, providing a material with high thermal conductivity is effective for transferring heat laterally to the solid-state laser medium 3. For example, sapphire has a thermal conductivity of 40 W / (m·K), which is higher than that of YAG, and has a refractive index and thermal expansion coefficient similar to those of YAG. Other materials that can be used include CVD diamond with a thermal conductivity of 1000 W / (m K) and SiC with a thermal conductivity of 200 W / (m K). As such, there are multiple candidates for the material to be used in the heat dissipation section, and it is not limited to a specific material.

[0074] It is also desirable to conduct heat in the in-plane direction perpendicular to the optical axis of the laser element, provide a heat propagation path to a support member (e.g., Cu with a thermal conductivity of 400 W / (m K)) arranged around the excitation light source 2 and the solid-state laser medium 3, and then dissipate the heat from the support member to the housing of the laser element package. In the laser element according to the present disclosure, a heat dissipation part is arranged between the excitation light source 2 made of laminated semiconductor layers and the solid-state laser medium 3, so that it is possible to prevent a decrease in the oscillation efficiency of the laser light and a decrease in the conversion efficiency of the light wavelength due to thermal interference without losing the advantage of a compact integrated structure.

[0075] Furthermore, it is necessary to make the transverse mode, which is the beam intensity distribution of the first wavelength of the first resonator 11, and the transverse mode, which is the beam intensity distribution of the second wavelength of the second resonator 12, substantially identical to each other to achieve mode coupling and maximize the output of the oscillation light from the second resonator 12. Therefore, it is desirable to consider the cooling efficiency and the transverse mode coupling efficiency when determining the thickness of the heat exhaust portion 13 between the pumping light source 2 and the solid-state laser medium 3, which forms part of the resonator length of the first resonator 11.

[0076] Furthermore, in order to efficiently couple the transverse mode, which is the beam intensity distribution of the first wavelength in the first resonator 11, with the transverse mode, which is the beam intensity distribution of the second wavelength in the second resonator 12, simply adjusting the thickness of the heat dissipation section 13 may result in an increase in thickness. This increases the length of the first resonator 11, causing diffraction loss of the first wavelength, and also increasing the overall length of the laser device 1.

[0077] By filling a part of the first resonator 11 with a highly refractive material and concentrating the first wavelength, it is possible to efficiently couple the transverse mode, which is the beam intensity distribution of the first wavelength, with the transverse mode, which is the beam intensity distribution of the second wavelength of the second resonator 12, without impairing the cooling performance or increasing the length of the first resonator 11, thereby maximizing the output of the oscillating light.

[0078] Furthermore, in the laser element according to the present disclosure, there is a risk that high peak intensity oscillation light from the short-pulse Q-switched laser light of the second wavelength may enter the pump light source to which it is joined as feedback light. Since the pump light source 2 is made of a material with a small band gap, optical damage due to multiphoton absorption by the short-pulse laser light is likely to occur. For this reason, it is desirable to arrange multiple short wavelength transmission filter films (SWPF) at multiple interfaces between the pump light source 2 and the solid-state laser medium 3 while shortening the cavity length, to prevent feedback light from entering the pump light source 2.

[0079] Various forms of the heat dissipation section will be described below.

[0080] (First form of heat exhaust part) Fig. 2 is a schematic cross-sectional view of a laser element 1 equipped with a heat dissipation unit 13 according to the first embodiment. The laser element 1 in Fig. 2 is mounted on a submount substrate 91, and the submount substrate 91 is mounted on a support substrate 92. The laser element 1 includes an excitation light source 2 made of laminated semiconductor layers, a heat dissipation unit 13, a solid-state laser medium 3, and a cooling member (second member) 14.

[0081] The excitation light source 2 in Fig. 2 has the same layer structure as, for example, the excitation light source 2 in Fig. 1, but the detailed layer structure is not shown in Fig. 2. By bringing the electrodes E1 and E2 shown in Fig. 1 into contact with the submount substrate 91 and connecting the submount substrate 91 and the support substrate 92 with a bonding wire 16, the current to be passed through the active layer 7 of the excitation light source 2 can be supplied from the support substrate 92 via the bonding wire 16.

[0082] The laser device 1 in Fig. 2 does not include the saturable absorber 4 of Fig. 1. Unlike Fig. 1, the second resonator 12 resonates light of the second wavelength λ2 between the second reflective layer R2 and the fourth reflective layer R4 in the solid-state laser medium 3. The fourth reflective layer R4 is disposed on the second surface F2 of the solid-state laser medium 3, or on the rear side of the second surface F2 along the optical axis.

[0083] 2 is joined to an end face of the excitation light source 2 and an end face of the solid-state laser medium 3, so that heat generated by the excitation light source 2 and the solid-state laser medium 3 is transferred to the heat exhaust part 13. The heat exhaust part 13 has, for example, a heat exhaust member (first member) 17 made of a material with a higher thermal conductivity than the solid-state laser medium 3. The material of the heat exhaust member 17 is, for example, sapphire or diamond, but is not limited to a specific material.

[0084] The pumping light source 2, the heat exhaust section 13, and the solid-state laser medium 3 are arranged on the same optical axis. A cooling member 14 is joined to each side of the pumping light source 2, the heat exhaust section 13, and the solid-state laser medium 3. The cooling member 14 is made of a metal material with high thermal conductivity, such as Cu. The cooling member 14 dissipates heat transferred from the pumping light source 2 and the solid-state laser medium 3 to the heat exhaust section 13. The cooling member 14 may be joined to a package (not shown) to dissipate heat using the package.

[0085] In the laser element 1 of Fig. 2, heat generated in the pumping light source 2 and the solid-state laser medium 3 is transferred to the heat exhaust section 13. The heat exhaust section 13 exhausts the heat from the pumping light source 2 and the solid-state laser medium 3 to the cooling member 14. This makes it possible to suppress temperature increases in the pumping light source 2 and the solid-state laser medium 3. Therefore, according to the laser element 1 of Fig. 2, it is possible to suppress thermal interference between the pumping light source 2 and the solid-state laser medium 3, prevent a decrease in the oscillation efficiency of the laser light in the pumping light source 2, and prevent a decrease in the light wavelength conversion efficiency in the solid-state laser medium 3.

[0086] Note that the heat dissipation unit 13 may be an air gap provided between the pumping light source 2 and the solid-state laser medium 3 instead of providing the heat dissipation member 17. By arranging the pumping light source 2 and the solid-state laser medium 3 at a distance so that they do not come into surface contact, heat transfer can be suppressed and thermal interference can be prevented. The cooling member 14 not only functions to cool the pumping light source 2 and the solid-state laser medium 3, but also to support the pumping light source 2 and the solid-state laser medium 3 while maintaining the air gap. Although air is present in the air gap, the thermal conductivity of air is lower than that of the pumping light source 2 and the solid-state laser medium 3, so heat transfer between the pumping light source 2 and the solid-state laser medium 3 can be suppressed and thermal interference between them can be prevented.

[0087] (Second form of heat exhaust part 13) 3 is a schematic cross-sectional view of a laser device 1 equipped with a heat dissipation portion 13 according to the second embodiment. The laser device 1 of FIG. 3 is obtained by adding a saturable absorber 4 to the laser device 1 of FIG. 2. As shown in FIG. 3, the saturable absorber 4 is bonded to an end face of the solid-state laser medium 3. The second resonator 12 in the laser device 1 of FIG. 3 resonates light of the second wavelength λ2 between the second reflective layer R2 in the solid-state laser medium 3 and the fourth reflective layer R4 in the saturable absorber 4, similar to FIG. 1.

[0088] The laser device 1 in FIG. 3 is provided with the heat exhaust section 13 similar to that in FIG. 2, and therefore thermal interference between the pumping light source 2 and the solid-state laser medium 3 can be suppressed.

[0089] (Third form of heat exhaust part 13) FIG. 4 is a schematic cross-sectional view of a laser device 1 equipped with a heat dissipation unit 13 according to a third embodiment. The laser device 1 of FIG. 4 has a two-layer structure in which a metal layer 18 with high thermal conductivity, such as Cu, is disposed on the surface of a heat dissipation member 17 made of sapphire or the like. The metal layer 18 is formed on the heat dissipation member 17 by, for example, vapor deposition or sputtering. Because the cooling member 14 is bonded to the sides of the cooling member 14, the heat dissipation unit 13, and the solid-state laser medium 3, disposing the metal layer 18 on the surface of the heat dissipation member 17 allows heat from the solid-state laser medium 3 to be efficiently transferred to the heat dissipation member 17 and the cooling member 14 via the metal layer 18, further improving the heat dissipation performance of the heat dissipation unit 13. However, because light of the first wavelength generates heat when absorbed by the metal layer, it is necessary to avoid the optical path of the first wavelength.

[0090] The laser device 1 in FIG. 4 does not include a saturable absorber 4, but a saturable absorber 4 may be bonded to the end face of the solid-state laser medium 3 in the same manner as in FIG.

[0091] (Fourth form of heat exhaust part 13) FIG. 5 is a schematic cross-sectional view of a laser device 1 including a heat dissipation section 13 according to a fourth embodiment. The laser device 1 of FIG. 5 differs from the first to third embodiments in the structure of the heat dissipation section 13. The heat dissipation section 13 of FIG. 5 has a first region 13a and a second region 13b. The first region 13a is a region including the optical axis and is disposed approximately in the center of the heat dissipation section 13. The first region 13a is a region that transmits light of the first wavelength. The first region 13a may be a transparent material layer that transmits light of the first wavelength, or may simply be an air gap. The second region 13b is disposed around the first region 13a and has a higher thermal conductivity than the solid-state laser medium 3. The second region 13b may be disposed as a plurality of vias. When the first region 13a is an air gap, the second region 13b functions as a spacer member for supporting the air gap of the first region 13a. The second region 13b is made of an insulating material or a metallic material, such as sapphire or diamond, which has high thermal conductivity.

[0092] The heat generated by the pumping light source 2 and the solid-state laser medium 3 is discharged in the second region 13b in the heat dissipation section 13. The second region 13b is joined to the pumping light source 2 and the solid-state laser medium 3, and is also joined to the cooling member 14, so that the heat transferred from the pumping light source 2 and the solid-state laser medium 3 can be discharged to the cooling member 14.

[0093] The second region 13b may be formed in a circular ring shape so as to surround the first region 13a, or may be formed by a plurality of vias.

[0094] (Fifth form of heat exhaust part 13) FIG. 6 is a schematic cross-sectional view of a laser device 1 equipped with a heat dissipation unit 13 according to a fifth embodiment. In the laser devices 1 of FIGS. 2 to 5, current is injected into the active layer 7 of the laser device 1 via a bonding wire 16. The bonding wire 16 is generally covered with a protective layer to prevent breakage. In the laser device 1 of FIG. 6, the protective layer of the bonding wire 16 and the cooling member 14 are integrated. Hereinafter, this integrated member will be referred to as the cooling member 14. The cooling member 14 of FIG. 6 is not only in contact with the side surfaces of the pumping light source 2, the heat dissipation member 17, and the solid-state laser medium 3, but is also arranged to cover the bonding wire 16. The protective layer of the bonding wire 16 of FIG. 6 is preferably coated with an insulating material. Known insulating coating materials include resin and glass, and are not limited to any specific material as long as the insulating material is used. The cooling member 14 is not limited to any specific material as long as it has a thermal conductivity higher than that of the solid-state laser medium 3.

[0095] A protective layer may be provided so as to cover the side surface of the cooling member and the bonding wires 16 in Fig. 5. In this case, the protective layer is provided separately from the cooling member.

[0096] (Sixth form of heat exhaust part 13) Fig. 7 is a schematic cross-sectional view of a laser element 1 including a heat dissipation portion 13 according to a sixth embodiment. The laser element 1 of Fig. 7 has a layer configuration of the heat dissipation portion 13 that is different from the heat dissipation portion 13 of Fig. 2 or 4. The heat dissipation portion 13 of Fig. 7 has a protective layer 19 laminated on the surface facing the laminated semiconductor layer 2. The protective layer 19 functions as a layer that transmits light of the first wavelength λ1 and reflects light of the second wavelength λ2.

[0097] By providing the protective layer 19 on the heat dissipation section 13, it is possible to suppress light leakage from the second resonator 12, and it is possible to improve the light emission efficiency of the excitation light source 2 and the light wavelength conversion efficiency of the solid-state laser medium 3. (Seventh form of heat exhaust part 13) FIG. 8 is a schematic cross-sectional view of a laser device 1 equipped with a heat exhaust unit 13 according to the seventh embodiment. A portion of the energy of the excitation light absorbed by the solid-state laser medium 3 in the laser device 1 according to the present disclosure is converted into heat, causing the temperature of the solid-state laser medium 3 to rise. This generates a temperature distribution within the solid-state laser medium 3, which in turn generates a refractive index distribution. In many solid-state laser media 3 made of inorganic materials, the refractive index generally increases with increasing temperature, with the refractive index gradually decreasing in the peripheral regions. This creates a virtual focusing lens called a thermal lens within the solid-state laser medium 3. This thermal lens effect focuses the laser light within the second resonator 12. Because the peak intensity of the laser light is increased within the second resonator 12 due to pulse shortening, focusing of the laser light due to the thermal lens effect significantly increases the likelihood of optical damage occurring within the first and second resonators 12. In particular, since the stacked semiconductor layer constituting the first resonator is made of a material with a small band gap, if leakage light of the laser light with the second wavelength λ2 generated in the second resonator 12 enters the first resonator, optical damage due to multiphoton absorption is likely to occur.

[0098] 8 includes, in addition to the heat dissipation unit 13, an optical element 41 that expands the beam diameter of the laser light of the second wavelength λ2 generated in the second resonator 12. The optical element 41 is disposed between the second reflective layer R2 and the fourth reflective layer R4 of the solid-state laser medium 3. When the laser element 1 does not include the saturable absorber 4, the fourth reflective layer R4 is disposed on the end face of the solid-state laser medium 3 on the light-emitting surface side, or on the rear side of this end face along the optical axis. When the laser element 1 includes the saturable absorber 4, the fourth reflective layer R4 is disposed on the end face of the saturable absorber 4 on the light-emitting surface side, or on the rear side of this end face along the optical axis.

[0099] The optical element 41 reflects or refracts at least a portion of the light of the second wavelength λ2 so that the light of the second wavelength λ2 is not concentrated. More specifically, the optical element 41 is a convex mirror that reflects at least a portion of the incident light so that the incident light is not concentrated, or a light refracting member that refracts at least a portion of the incident light.

[0100] FIG. 8 shows an example in which an optical element 41 is provided on the end surface of the saturable absorber 4 on the light-emitting side. The optical element 41 is formed by processing the end surface of the solid-state laser medium 3 side of a base material made of a material that transmits light of the first wavelength and the second wavelength λ2 into a concave shape, and then forming, for example, a multilayer film along the concave surface, and arranging a convex mirror 42. This convex mirror 42 functions as the fourth reflective layer R4 of the second resonator 12. Light of the second wavelength λ2 incident on this convex mirror 42 is reflected so as not to be focused. This allows the beam diameter of the light of the second wavelength λ2 in the second resonator 12 to be expanded, the peak power of the laser light to be reduced, and optical damage to the solid-state laser medium 3 and the pumping light source 2 to be reduced. In FIG. 8, a heat dissipation member 17 is provided on the underside of the convex mirror 42, and the side of the heat dissipation member 17 that is bonded to the convex mirror 42 is processed into a concave shape.

[0101] (Eighth form of heat exhaust part 13) FIG. 9 is a schematic cross-sectional view of a laser element 1 equipped with a heat dissipation unit 13 according to an eighth embodiment. The heat dissipation unit 13 in the laser element 1 of FIG. 9 includes a heat dissipation member 17 having an active cooling function. For example, the heat dissipation member 17 has a function of storing and circulating a refrigerant 17a. As a specific implementation example, the optical axis portion of the excitation light may be made of a transparent material, and a heat pipe 17b storing a refrigerant may be provided around the transparent material. Alternatively, instead of the heat pipe 17b, a micro-channel leading to the outside of the laser element may be provided in the heat dissipation member 17 to circulate the refrigerant 17a. Forced cooling by the refrigerant 17a allows efficient heat dissipation from the laser medium 3. The refrigerant 17a may be liquid or gas.

[0102] (9th form of heat exhaust part 13) FIG. 10 is a schematic cross-sectional view of a laser device 1 equipped with a heat dissipation unit 13 according to the ninth embodiment. The laser device 1 of FIG. 10 includes a light control member (polarization control element) 43 in addition to the heat dissipation unit 13. The light control member 43 is disposed, for example, between the solid-state laser medium 3 and the saturable absorber 4, or further rearward of the saturable absorber 4 along the optical axis. The light control member 43 controls the refraction, diffraction, or polarization direction of light of the second wavelength λ2. More specifically, the light control member 43 is, for example, a photonic crystal layer. The photonic crystal layer is a layer in which the refractive index changes periodically. The photonic crystal layer can select either P-polarized light or S-polarized light. The light control member 43 may also be a diffraction grating.

[0103] The light control member 43 may have a fine periodic structure. More specifically, the fine periodic structure is, for example, a Fresnel lens, a metasurface structure, or a photonic crystal lens. By adjusting the period and size of the concave and convex portions that make up the fine periodic structure, the refraction, diffraction, or polarization direction of light with the second wavelength λ2 can be controlled.

[0104] (10th form of heat exhaust part 13) 11A, 11B, 11C, and 11D are schematic diagrams illustrating the planar shape of a heat dissipation unit 13 according to the tenth embodiment. The heat dissipation unit 13 illustrated in FIGS. 11A to 11C has a basic structure similar to that of the heat dissipation unit 13 according to any one of the first to eighth embodiments described above, with additional technical features added to the basic structure. The heat dissipation unit 13 illustrated in FIGS. 11A to 11C has a cooling member 14 with a polygonal planar shape, in which the optical axis of the laser light is located at the center. A heat dissipation member 17 such as sapphire may be disposed around the optical axis of the laser light, or an air gap may be used. Because the temperature of the laser light is highest at the optical axis, a structure in which heat is evenly transferred to the heat dissipation member 17 disposed around the optical axis is desirable. Therefore, in FIGS. 11A to 11C, the planar shape of the cooling member 14 is a regular n-gon (n is an integer greater than or equal to 3), and the center of the regular n-gon is the optical axis of the laser element 1. 11D, the optical axis of the laser light is positioned at the center of the cooling member 14, which has a circular planar shape. This makes the distance from each vertex of the regular n-gon or circle to the optical axis equal, allowing heat to be transferred evenly throughout the entire area of ​​the heat dissipation unit 13 and dissipated by the cooling member 14.

[0105] (11th form of heat exhaust part 13) FIG. 12 is a schematic cross-sectional view of a laser array 44 in which a plurality of lens elements are arranged in a one-dimensional or two-dimensional direction. While FIG. 12 shows an example in which each lens element has a heat dissipation section 13 having the same structure as FIG. 2, the lens elements may have a heat dissipation section 13 according to any of the second to tenth embodiments. The heat dissipation sections 13 of the plurality of lens elements are joined together. The integrally structured heat dissipation section 13 has a heat dissipation member 17. A cooling member 14 is joined to the side of the lens array having a plurality of lens elements. The cooling member 14 is joined to the heat dissipation member 17. As a result, heat generated by the excitation light source 2 and the solid lens medium in each lens element is transferred to the heat dissipation member 17 and dissipated from the heat dissipation member 17 to the cooling member 14.

[0106] (Temperature distribution of heat exhaust section 13) 13A, 13B, 13C, and 13D are diagrams showing the temperature distribution of the laser light sources at the center and corners of the laser array 44 when the heat dissipation unit 13 is provided and when it is not provided. Fig. 13A and Fig. 13B show the temperature distribution of the laser light sources at the center of the laser array 44, Fig. 13A shows the case when the heat dissipation unit 13 is not provided, and Fig. 13B shows the case when the heat dissipation unit 13 is provided. Fig. 13C and Fig. 13D show the temperature distribution of the laser light sources at the corners of the laser array 44, Fig. 13C shows the case when the heat dissipation unit 13 is not provided, and Fig. 13D shows the case when the heat dissipation unit 13 is provided.

[0107] The horizontal axis in Figures 13A to 13D indicates the position on the optical axis of the laser element 1, with the fourth reflective layer R4 side of the solid-state laser medium 3 on the left side of the horizontal axis and the support substrate 92 side on the right side of the horizontal axis. The vertical axis in Figures 13A to 13D indicates the temperature at each position. Figures 13A and 13C show the temperature distribution w1 of a laser element 1 that does not have a heat dissipation unit 13. Figures 13B and 13D show the temperature distributions w2 to w5 of four types of laser elements 1 that have different heat dissipation units 13. Temperature distribution w2 shows the temperature distribution of a laser element 1 that has a heat dissipation unit 13 with a sapphire heat dissipation member 17, temperature distribution w3 shows the heat dissipation unit 13 with a sapphire heat dissipation member 17 and a cooling member 14, temperature distribution w4 shows the heat dissipation unit 13 with a diamond heat dissipation member 17 and a cooling member 14, and temperature distribution w5 shows the temperature distribution of a laser element 1 that has a heat dissipation unit 13 with an air gap and a cooling member 14. The cooling member 14 is a copper wall joined to the side surfaces of the pumping light source 2, the heat exhaust portion 13, and the solid-state laser medium 3.

[0108] As shown in the figure, the laser elements 1 in the center of the laser array 44 have a higher temperature overall than the corners, both with and without the heat dissipation section 13. Furthermore, among the four types of heat dissipation section 13, the laser elements 1 equipped with the heat dissipation section 13 having the heat dissipation member 17 made of diamond and the cooling member 14 (temperature distribution w5) have the greatest temperature reduction effect. The next greatest temperature reduction effect is achieved by the laser elements 1 equipped with the heat dissipation section 13 having the heat dissipation member 17 made of sapphire and the cooling member 14 (temperature distribution w4), and the next greatest temperature reduction effect is achieved by the laser elements 1 equipped with the heat dissipation section 13 having the heat dissipation member 17 made of sapphire but no cooling member 14 (temperature distribution w3). The laser elements 1 equipped with the heat dissipation section 13 and the cooling member 14 made of an air gap (temperature distribution w2) have the smallest temperature reduction effect, but the air gap alone can reduce the temperature more than the laser elements 1 equipped with no air gap (temperature distribution w1). Therefore, the heat dissipation section 13 can achieve a certain degree of effect in suppressing the temperature rise inside the laser element 1 even if it is only an air gap.

[0109] (Countermeasures against return light) Furthermore, when the second resonator 12 emits a laser pulse of the second wavelength λ2 by Q-switching, there is a risk that the high peak intensity of the oscillation light of the second wavelength λ2 may enter the pumping light source 2 as feedback light. Because the pumping light source 2 is made of a semiconductor material with a small bandgap, there is a risk that it may be destroyed by the feedback light. For this reason, it is desirable to arrange a heat dissipation unit 13 and a plurality of short wavelength transmission filter films (SWPFs) as protective layers 19 between the pumping light source 2 and the solid-state laser medium 3 while shortening the resonator length, to prevent the feedback light from entering the pumping light source 2.

[0110] (Method for manufacturing laser device 1 of the present disclosure) Fig. 14 is a diagram schematically illustrating the manufacturing process of the laser device 1 of the present disclosure. Fig. 14 illustrates the manufacturing process of the laser device 1 including the optical element 41 for avoiding optical damage and the saturable absorber 4 shown in Fig. 8. Fig. 14 also illustrates an example in which a convex mirror 42 for the optical element 41 is formed on the upper surface side of the saturable absorber.

[0111] First, as shown in step S1 of FIG. 10, a resist film 21 is applied onto a transparent substrate 45 for an optical element 41 to be placed on the saturable absorber 4, and a photomask 22 is placed on the resist film 21, followed by UV exposure.

[0112] Next, as shown in step S2, the exposed areas and the resist film 21 are removed by dry etching or the like to form a plurality of recesses 23 on the upper surface of the transparent substrate 45. A dielectric multilayer film 24 is formed in the plurality of recesses 23 by vapor deposition, sputtering, or the like to form a convex mirror 42.

[0113] Next, as shown in step S3, the laminated semiconductor layer 2 for the excitation light source 2, the heat exhaust member 17, the solid-state laser medium 3, and the saturable absorber 4 processed in step S2 are vertically arranged and aligned. Note that the heat exhaust member 17 is formed by depositing sapphire, diamond, or the like on the upper surface of the laminated semiconductor layer 2 by vapor deposition or sputtering before step S3.

[0114] At this time, as shown in step S4, alignment marks 25 provided at specific locations on the semiconductor layer 2, the solid-state laser medium 3, and the saturable absorber 4 are photographed with a camera 26, and the semiconductor layer 2, the solid-state laser medium 3, and the saturable absorber 4 are aligned and bonded so that the alignment marks 25 are aligned vertically. Next, as shown in step S5, the resultant is singulated into individual laser elements by dicing.

[0115] (Effects of laser device 1 of the present disclosure) As described above, in the laser element 1 of the present disclosure, the heat exhaust unit 13 is provided between the pumping light source 2 and the solid-state laser medium 3, so that heat generated by at least one of the pumping light source 2 and the solid-state laser medium 3 can be exhausted. In particular, by using the heat exhaust member 17 made of a material with a higher thermal conductivity than the solid-state laser medium 3, such as sapphire or diamond, as the heat exhaust unit 13, the heat generated by the pumping light source 2 and the solid-state laser medium 3 can be efficiently exhausted. Furthermore, by joining the cooling member 14 made of Cu or the like to the side surfaces of the pumping light source 2, the heat exhaust unit 13, and the solid-state laser medium 3, the heat generated by the pumping light source 2 and the solid-state laser medium 3 can be dissipated to the cooling member 14 via the heat exhaust member 17, and a temperature rise in the laser element 1 can be suppressed.

[0116] In the laser device 1 according to the present disclosure, the first resonator 11 and the second resonator 12 share the solid-state laser medium 3. Furthermore, the light transmitting surfaces of all optical components in the laser device 1, including the pumping light source 2, the solid-state laser medium 3, and the saturable absorber 4, are bonded and fixed by a bonding process. Furthermore, by providing the above-mentioned heat exhaust unit 13 between the pumping light source 2 and the solid-state laser medium 3, it is possible to suppress a temperature rise in the laser device 1. This improves the reliability and mass productivity of the laser device 1, and enables a high-performance laser device 1 to be obtained at low cost.

[0117] According to the present disclosure, since the solid-state laser medium 3 is bonded to the excitation light source 2, the solid-state laser medium 3 is excited by a standing wave within the excitation light source 2. By designing a resonator that confines excitation light within the first resonator 11, even if the solid-state laser medium 3 is not thick enough to absorb the excitation light when the laser light passes through the first resonator 11 only once, the laser light travels back and forth multiple times, so that the excitation light can ultimately be sufficiently absorbed by the solid-state laser medium 3. This allows for shorter pulse Q-switched laser oscillation without reducing excitation efficiency.

[0118] In conventional Q-switched solid-state lasers, the solid-state laser medium 3 is excited by a traveling wave, and the method of excitation is significantly different from that of the laser element 1 according to the present disclosure. The laser element 1 according to the present disclosure can solve the above-mentioned trade-off that the absorption amount of excitation light decreases when the solid-state laser medium 3 is shortened.

[0119] Furthermore, according to the laser device 1 of the present disclosure, by directly bonding the light transmitting surfaces of the optical components, it is possible to suppress short-term and long-term fluctuations in the laser output caused by mechanical misalignment. Furthermore, since all the optical components can be bonded and then diced to separate them into individual laser light sources, mass productivity can be improved.

[0120] Conventionally, five-axis optical adjustment (X, Y, Z, θ, φ) for the optical axis, decentering, and focus is performed for the excitation light source 2 and second resonator 12 using multiple lenses including a collimator lens and a condenser lens. Furthermore, if an optical element 9 with a beam divergence function (negative refractive power) is added to the second resonator 12, it becomes even more difficult to adjust the position of the optical element 9 with precision.

[0121] However, in the laser element 1 according to the present disclosure, instead of using multiple lenses such as collimator lenses and condenser lenses, the light emitting point of the excitation light source 2 and the center position of the convex mirror 42 of the optical element 9 are aligned by bonding using an alignment mark 25 or the like, thereby eliminating the need to adjust the focus position accuracy in the thickness (Z axis) direction or the tilt in the θ and φ directions. Therefore, the laser element 1 according to the present disclosure makes it possible to suppress short-term and long-term fluctuations in the laser output, facilitating optical adjustment to obtain oscillation light from the excitation light source 2, and realizing a light source with improved mass productivity.

[0122] Furthermore, the laser device 1 according to the present disclosure employs an integrated laminated structure in which the optical axis of the first resonator 11 and the optical axis of the second resonator 12 are coaxial. The laser device 1 according to the present disclosure does not require complex positional and angular alignment, simplifying the structure. This makes it easy to miniaturize the laser device 1.

[0123] Furthermore, a plurality of laser elements 1 according to the present disclosure can be simultaneously formed on the same semiconductor substrate 5 by stacking or bonding a plurality of materials. After simultaneously forming a plurality of laser elements 1, dicing is performed in a post-process to separate each laser element 1, thereby enabling mass production of high-performance laser elements 1 at low cost. Furthermore, the laser element 1 according to the present disclosure can easily produce a laser array 44 in which a plurality of laser elements 1 are two-dimensionally arranged on a single substrate.

[0124] Furthermore, in the laser device 1 according to the present disclosure, the repetition frequency of the laser pulse can be adjusted depending on the type of solid-state laser medium 3. In particular, the laser device 1 according to the present disclosure has a high gain density, and therefore the repetition frequency of the laser pulse can be increased. Furthermore, in the laser device 1 according to the present disclosure, the cavity length can be changed simply by adjusting the thickness of the solid-state laser medium 3, the Q switch (saturable absorber 4), and the wavelength conversion material (nonlinear optical crystal). In other words, the pulse time width of the laser pulse can be changed depending on the thickness of the material, and therefore the characteristics of the laser pulse can be easily adjusted. In particular, shortening the pulse time width of the laser pulse can improve processing accuracy in the field of micromachining.

[0125] Furthermore, by arranging the laser elements 1 according to the present disclosure in a one-dimensional or two-dimensional array, a laser device that achieves both high processing accuracy and high output energy can be obtained. Also, the laser element 1 according to the present disclosure can be applied to other fields such as highly efficient wavelength conversion technology, medical equipment, and distance measurement.

[0126] The laser element 1 in FIG. 1 shows an example in which the pumping light source 2, the solid-state laser medium 3, and the saturable absorber 4 are integrally bonded together, but as shown in FIG. 15 , a first transparent medium 27 that transmits light of the first wavelength λ1 may be disposed between the pumping light source 2 and the solid-state laser medium 3.

[0127] 15, a second transparent medium 28 that transmits light of the second wavelength λ2 may be disposed between the solid-state laser medium 3 and the saturable absorber 4. Note that only one of the first transparent medium 27 and the second transparent medium 28 may be disposed.

[0128] In this way, the pumping light source 2, the solid-state laser medium 3, and the saturable absorber 4 do not necessarily have to be joined together.

[0129] 15, the optical element 9 may be arranged further rearward on the optical axis than the saturable absorber 4. In the optical element 9 of FIG. 15, a transparent member 29 that transmits light of the second wavelength λ2 is processed into a concave shape to form a convex mirror 42. In the case of FIG. 15, the optical axis of the pumping light source 2, the optical axis of the solid-state laser medium 3, the optical axis of the saturable absorber 4, and the optical axis of the optical element 9 must be arranged on the same axis.

[0130] (Laser element 1 without saturable absorber 4) FIG. 1 shows an example in which the laser element 1 is equipped with a saturable absorber 4 and emits short-pulse pulsed laser light, but even in a laser element 1 that does not have a saturable absorber 4 and emits CW laser light, there is a risk of thermal interference occurring between the excitation light source 2 and the solid-state laser medium.

[0131] FIG. 16 is a diagram showing the basic configuration of a laser device 1 that does not have a saturable absorber 4. The laser device 1 in FIG. 16 has a configuration in which the saturable absorber 4 is omitted from FIG. 1. Similar to FIG. 1, the first resonator 11 resonates light of a first wavelength λ1 between the first reflective layer R1 in the pumping light source 2 and the third reflective layer R3 in the solid-state laser medium 3. On the other hand, unlike FIG. 1, the second resonator 12 resonates light of a second wavelength λ2 between the second reflective layer R2 and the fourth reflective layer R4 in the solid-state laser medium 3. The fourth reflective layer R4 is disposed on the second surface F2 of the solid-state laser medium 3 or on the rear side of the second surface F2 along the optical axis.

[0132] Fig. 16 shows an example in which the third reflective layer R3 and the fourth reflective layer R4 are separately provided along the second surface F2 of the solid-state laser medium 3. When the fourth reflective layer R4 is disposed on the rear side of the optical axis relative to the third reflective layer R3 as in Fig. 16, the third reflective layer R3 needs to have the property of transmitting light of the second wavelength λ2.

[0133] The third reflective layer R3 is a highly reflective layer, while the fourth reflective layer R4 is a partially reflective layer. Therefore, the power of the excitation light of the first wavelength is confined within the solid-state laser medium 3. When the solid-state laser medium 3 is sufficiently excited and the output of the spontaneous emission light increases, the light of the second wavelength λ2 passes through the fourth reflective layer R4 and is emitted from the laser element 1.

[0134] Alternatively, the third reflective layer R3 and the fourth reflective layer R4 may be integrated into a single reflective layer, which reflects light of the first wavelength and light of the second wavelength λ2.

[0135] The configuration in which the heat exhaust section 13 is provided between the pumping light source 2 and the solid-state laser medium 3 in the laser device 1 of FIG. 16 is, for example, that shown in FIG. 2, FIG. 4, FIG. 5, FIG. 6, or FIG.

[0136] (laser amplifier) The structure of the laser device 1 according to the present disclosure described above can be applied to a laser amplifying device. Conventionally, in order to avoid optical damage, short-pulse laser light has been amplified by devising and implementing a method of amplifying the light by lowering the peak intensity of the amplified light. For example, there is the chirped pulse amplification method, in which the pulse width of the laser light is first widened and then amplified in that state, and then the pulse width is compressed, as well as the thin disk type and slab type methods, in which the laser light beam is spatially widened to lower its peak intensity. However, all of these methods require a large and complex optical system, making miniaturization difficult and expensive.

[0137] In particular, in recent years, Innoslab technology (developed by the Fraunhofer Institute in Germany and commercialized by EdgeWave and AMPHOS), an amplifier with a slab structure, has become a hot topic as a technology for increasing the output power of laser light. Fig. 17A is a perspective view showing the configuration of Innoslab, Fig. 17B is a plan view of Fig. 17A as seen from the Y direction, and Fig. 17C is a plan view as seen from the Z direction.

[0138] As shown in these figures, Innoslab includes two pump light sources 81 and 82 provided on both sides in the X direction, mirrors M1 to M6, an amplification medium 83, a polarizer 84, and a λ / 4 plate 85. Each of the pump light sources 81 and 82 includes a laser array 86, optical systems L1 to L3, and a waveguide 87.

[0139] Weak light to be amplified (light to be amplified) is input from the input section IN. This light to be amplified travels back and forth many times between mirrors M2 and M5, slightly shifting its path. Each time the light to be amplified passes through the amplifying medium 83 located between mirrors M2 and M5, it is amplified by stimulated emission in the amplifying medium 83, and finally, amplified laser light is emitted from the output section OUT.

[0140] A plurality of laser arrays 86 in the excitation light sources 81 and 82 are stacked in the Z direction and emit laser light in a plane in the X direction. The laser light emitted in a plane from the laser array 86 is collected by a cylindrical lens L1 and enters a waveguide 87. The laser light emitted from the waveguide 87 is beam-shaped by a cylindrical lens L2 and an optical system L3 and enters a half mirror M4. A portion of the laser light that enters the half mirror M4 passes through the half mirror M4 and enters the amplification medium 83.

[0141] In many cases, Nd:YAG or Yb:YAG is used as the amplification medium 83. The amplification medium 83 is thin (e.g., 0.2 mm × 10 mm × 10 mm), and the light to be amplified is incident on a long, narrow rectangular end face. The light to be amplified is so-called seed light, which is a laser pulse emitted from a femtosecond laser or a picosecond laser oscillator.

[0142] 17A to 17C has two advantages. The first advantage is that the heat flux in the gain medium 83 is one-dimensional, so thermal lensing and thermal birefringence, which limit the amplification factor of laser light, do not occur. Thermal lensing and thermal birefringence occur significantly in rod-type gain medium 83, and limit the amplification factor of laser light.

[0143] The second advantage is that since the seed light is incident from the end face of the elongated rectangle described above, the beam shape of the seed light can be elongated in the longitudinal direction, and the peak intensity in the amplification medium 83 can be spatially reduced, thereby preventing optical damage caused by the amplified light.

[0144] On the other hand, Innoslab also has its drawbacks. As shown in Figures 17A to 17C, Innoslab typically employs a configuration in which pumping is performed from both sides of the amplifying medium 83, resulting in a longitudinal length of nearly 1 m. This is because a complex beam shaping optical system is required to shape the light beam from the edge-emitting LD module into a beam that matches the rectangular end face of the amplifying medium 83.

[0145] Furthermore, as a more fundamental issue, the amplification factor of laser light in Innoslab is determined by the area of ​​the amplification medium 83 when the thickness of the amplification medium 83 is constant, and this area is determined by the optical absorption length of the pumping light in the amplification medium 83. This is because the principle of the Innoslab method is a so-called end-pump type amplifier configuration, and there is a limit to the amplification factor of laser light that is determined by the optical absorption length of the pumping light.

[0146] For example, if Yb:YAG is used as the amplifying medium 83 and the wavelength of the excitation light is 940 nm, the excitation light is absorbed approximately 5 mm from the incident surface of the Yb:YAG. Since the Yb:YAG is excited from both sides, the length of the Yb:YAG is set to approximately 10 mm. If the length of the Yb:YAG is made longer than 10 mm, an unexcited region will be created inside the Yb:YAG. For this reason, the amplification medium 83 can only achieve an amplification factor of the length determined by the absorption length of the excitation light. Therefore, the upper limit of the amplification factor is determined by the size of the amplifying medium 83, which is determined by the absorption length of the excitation light.

[0147] Fig. 18A is a cross-sectional view of the laser amplification element 50 according to the present disclosure, Fig. 18B is a perspective view of the laser amplification element 50 according to the present disclosure, and Fig. 18C is a plan view schematically showing the optical path of the laser light within the laser amplification element 50.

[0148] 18A to 18C includes an excitation light source 53 disposed on a support substrate 51 via a submount substrate 52, and a solid-state laser medium 54 disposed on the excitation light source 53, and does not include a saturable absorber 4. The solid-state laser medium 54 is, for example, Yb:YAG. As will be described later, the excitation light source 53 and the solid-state laser medium 54 form a first resonator 55, and light of the first wavelength resonates in the vertical direction (stacking direction) of FIG. 18A. More specifically, the first resonator 55 resonates light of the first wavelength between a first reflective layer R1 (p-DBR 72) in the excitation light source 53 and a second reflective layer R2 in the solid-state laser medium 54. The solid-state laser medium 3 in the laser element 1 in FIG. 1 has a second reflecting layer R2 on the end face facing the excitation light source 2 and a third reflecting layer R3 on the end face facing the saturable absorber 4, but the solid-state laser medium 54 in FIG. 18A does not need a reflecting layer on the end face facing the excitation light source 53, and has a second reflecting layer R2 on the end face opposite to that.

[0149] 18A to 18C includes a first reflecting member 56 and a second reflecting member 57 arranged along the opposing first side surface 54S1 and second side surface 54S2 of the solid-state laser medium 54, and the solid-state laser medium 54 functioning as an amplifying medium 83 that causes light of the second wavelength λ2 to travel back and forth multiple times between the first reflecting member 56 and the second reflecting member 57.

[0150] The first reflecting member 56 and the second reflecting member 57 may have flat reflecting mirrors, or may have convex reflecting mirrors to avoid optical damage to the material due to the increased light density during the amplification process.

[0151] In FIG. 18A, the first reflecting member 56 and the second reflecting member 57 are arranged at a distance from the first side surface 54S1 and the second side surface 54S2 of the solid-state laser medium 54, but a multilayer film formed by stacking at least one of a semiconductor material, a metal material, and a dielectric material on the first side surface 54S1 and the second side surface 54S2 may be used as a reflecting mirror.

[0152] 18A to 18C further includes an optical input portion IN provided along the first side surface 54S1 and an optical output portion OUT provided along the second side surface 54S2. The optical input portion IN inputs weak light (seed light) having a second wavelength λ2 to the first side surface 54S1. The light having the second wavelength λ2 travels back and forth through the amplifying medium 83 multiple times and is emitted from the optical output portion OUT.

[0153] 18A to 18C may also include a first heat exhaust member 60 and a second heat exhaust member 61. The first heat exhaust member 60 is disposed between the pumping light source 53 and the solid-state laser medium 54, and exhausts heat generated by at least one of the pumping light source 53 and the solid-state laser medium 54. The second heat exhaust member 61 is joined to the end face of the solid-state laser medium 54 opposite to the end face facing the pumping light source 53, and exhausts heat generated by the solid-state laser medium 54.

[0154] If the thermal interference between the excitation light source 53 and the solid-state laser medium 54 is not large, at least one of the first heat exhaust member 60 and the second heat exhaust member 61 may be omitted.

[0155] The first heat exhaust member 60 and the second heat exhaust member 61 are made of a material, such as sapphire or YAG, that has a higher thermal conductivity than the solid-state laser medium 54. The first heat exhaust member 60 and the second heat exhaust member 61 are made of a transparent material that transmits light of the first wavelength.

[0156] 18A to 18C may also include a cooling member 62. The cooling member 62 is joined to the side surfaces of the pumping light source 53, the first heat dissipation member 60, and the solid-state laser medium 54, and dissipates heat transferred from at least one of the pumping light source 53 and the solid-state laser medium 54 to the first heat dissipation member 60. The cooling member 62 is made of a metal material with high thermal conductivity, such as Cu. The cooling member 62 may be joined to a package (not shown), or heat may be dissipated from the cooling member 62 to the package.

[0157] 18A to 18C, a support substrate 51 is, for example, a Cu substrate, and a submount substrate 52 is disposed thereon. The submount substrate 52 has, for example, a laminated structure of a SiC layer 64 and an AuSn layer 65, and a p-electrode 73 and an n-electrode 74 of an excitation light source 53 are bonded onto the AuSn layer 65 while being electrically insulated from each other.

[0158] The pumping light source 53 is a laminated semiconductor layer formed by sequentially stacking an n-contact layer 67, an n-DBR 68, a cladding layer 69, an active layer 70, a cladding layer 71, and a p-DBR 72 on an n-GaAs substrate 66. P-electrodes 73 and n-electrodes 74 are alternately disposed on the p-DBR 72. The p-electrode 73 is electrically connected to the p-DBR 72, and the n-electrode 74 is electrically connected to the n-DBR 68 through a via 75.

[0159] The laser amplifier device 50 according to the present disclosure includes a first resonator 55, similar to that shown in FIG. 1. The first resonator 55 resonates light of a first wavelength between a first reflective layer R1 in the excitation light source 53 and a second reflective layer R2 in the solid-state laser medium 54. The first reflective layer R1 is a p-DBR 72, and the second reflective layer R2 is disposed, for example, on the upper surface of the second heat dissipation member 61. The solid-state laser medium 54 is excited by the resonant action of the light of the first wavelength by the first resonator 55. In FIG. 18A, the resonant action by the first resonator 55 is schematically indicated by a thin line. Amplified light (seed light) of a second wavelength λ2 is incident on the excited solid-state laser medium 54 from the right end to the left in FIG. 18A. This causes stimulated emission of the amplified light, and the amplified light is laser-amplified.

[0160] Furthermore, when Yb:YAG is used as the amplifying medium 83, if laser light with a wavelength of 1030 nm is used as the seed light, the seed light will be absorbed in the unexcited region of the amplifying medium 83, resulting in a problem of insufficient amplification. For this reason, when Yb:YAG is used as the amplifying medium 83, seed light with a wavelength of 1050 nm, which does not cause optical absorption even in the unexcited state, can be used. In this case, the wavelength of the seed light is not limited to 1050 nm, as long as it does not cause optical absorption even in the unexcited state.

[0161] In this way, by providing the solid-state laser medium 54 inside the first resonator 55, the two excitation light sources 53 that were required when exciting the solid-state laser medium 54 from both end faces of the solid-state laser medium 54 as shown in FIGS. 17A to 17C are no longer necessary, and the optical configuration can be significantly simplified and made smaller.

[0162] Furthermore, the size of the solid-state laser medium 54 in the laser amplifying element 50 according to the present disclosure is not limited by the absorption length of the pumping light, and therefore the area of ​​the solid-state laser medium 54 can be increased regardless of the absorption length of the pumping light. By increasing the area of ​​the solid-state laser medium 54, the amplification factor of the laser amplifying element 50 can be further improved.

[0163] Furthermore, the laser amplification element 50 according to the present disclosure can integrally bond the excitation light source 53 made of laminated semiconductor layers and the solid-state laser medium 54, and can be manufactured using a general-purpose semiconductor process, which makes it easy to miniaturize the element and reduces manufacturing costs.

[0164] Furthermore, the laser amplification element 50 according to the present disclosure has the first heat dissipation member 60 and the second heat dissipation member 61 joined to both sides of the solid-state laser medium 54, thereby suppressing a rise in temperature of the solid-state laser medium 54 and preventing thermal interference between the excitation light source 53 and the solid-state laser medium 54.

[0165] In order to efficiently dissipate heat from the pumping light source 53 and the solid-state laser medium 54 to the first heat dissipation member 60, a plurality of via members 76 may be provided in the first heat dissipation member 60. FIG. 19A is a cross-sectional view of the laser amplification element 50 in which the heat dissipation performance of the first heat dissipation member 60 of FIG. 18A has been improved. The first heat dissipation member 60 of FIG. 19A has a plurality of via members 76 that penetrate the first heat dissipation member 60 and are joined to the pumping light source 53 and the solid-state laser medium 54. These via members 76 are filled with a material that has a higher thermal conductivity than the base material of the first heat dissipation member 60.

[0166] Fig. 19B is a cross-sectional view taken along line AA in Fig. 19A. Fig. 19B shows an example in which a plurality of via members 76 are arranged at regular intervals in a two-dimensional direction, but the arrangement location, diameter size, and number of the via members 76 are arbitrary. Since the thermal conductivity of the plurality of via members 76 is higher than the thermal conductivity of the solid-state laser medium 54, the heat transferred from the excitation light source 53 and the solid-state laser medium 54 to the via members 76 is discharged to the cooling member 62 via the first heat discharge member 60.

[0167] As described above, in the laser amplifying element 50 shown in FIGS. 18A to 18C or 19A to 19B, the first resonator 55, which is composed of the first reflective layer R1 in the excitation light source 53 and the second reflective layer R2 in the solid-state laser medium 54, resonates the light of the first wavelength in the stacking direction, thereby putting the solid-state laser medium 54 into an excited state, and in this state, the light of the second wavelength λ2 is made incident in the horizontal direction from the end face of the solid-state laser medium 54 and is reflected multiple times between two reflective mirrors provided along the two opposing end faces of the solid-state laser medium 54, thereby making it possible to sufficiently amplify and emit the light of the second wavelength λ2.

[0168] 18A to 18C or 19A to 19B has a structure in which the pumping light source 53 and the solid-state laser medium 54 are integrated, and can be formed using semiconductor process technology, so that the solid-state laser medium 54 can be pumped despite its small size. Furthermore, the light of the second wavelength λ2 to be optically amplified is incident horizontally from the end face of the solid-state laser medium 54 and is repeatedly reflected by the first reflecting member 56 and the second reflecting member 57 arranged along two opposing side faces 54S1 and 54S2 of the solid-state laser medium 54, thereby amplifying the light of the second wavelength λ2. Therefore, the light can be optically amplified with a sufficient amplification factor despite its small size.

[0169] <<Application Example>> The technology disclosed herein can be widely applied to medical imaging systems (hereinafter also referred to as electronic devices), ranging systems such as LiDAR (Light Detection and Ranging) devices, light sources for laser processing devices, etc. Medical imaging systems are medical systems that use imaging technology, such as endoscope systems and microscope systems.

[0170] [Endoscope system] An example of an endoscopic system will be described with reference to FIGS. 20 and 21. FIG. 20 is a diagram illustrating an example of a schematic configuration of an endoscopic system 5000 to which the technology according to the present disclosure can be applied. FIG. 21 is a diagram illustrating an example of the configuration of an endoscope 5001 and a CCU (Camera Control Unit) 5039. FIG. 20 illustrates a state in which an operator (e.g., a doctor) 5067, who is a surgical participant, is performing surgery on a patient 5071 on a patient bed 5069 using the endoscopic system 5000. As shown in FIG. 20, the endoscopic system 5000 includes an endoscope 5001, which is a medical imaging device, a CCU 5039, a light source device 5043, a recording device 5053, an output device 5055, and a support device 5027 that supports the endoscope 5001.

[0171] In endoscopic surgery, an insertion aid called a trocar 5025 is inserted into a patient 5071. Then, a scope 5003 and surgical tools 5021 connected to an endoscope 5001 are inserted into the body of the patient 5071 via the trocar 5025. The surgical tools 5021 are, for example, energy devices such as an electric scalpel, forceps, etc.

[0172] A surgical image, which is a medical image showing the inside of the body of a patient 5071 photographed by an endoscope 5001, is displayed on a display device 5041. An operator 5067 performs a procedure on the surgical target using a surgical tool 5021 while viewing the surgical image displayed on the display device 5041. Note that the medical image is not limited to a surgical image, and may be a diagnostic image photographed during a diagnosis.

[0173] [Endoscopy] The endoscope 5001 is an imaging unit that captures images of the inside of the body of a patient 5071. For example, as shown in FIG. 21 , the endoscope 5001 is a camera 5005 that includes a focusing optical system 50051 that focuses incident light, a zoom optical system 50052 that enables optical zoom by changing the focal length of the imaging unit, a focus optical system 50053 that enables focus adjustment by changing the focal length of the imaging unit, and a light-receiving element 50054. The endoscope 5001 generates pixel signals by focusing light onto the light-receiving element 50054 via a connected scope 5003, and outputs the pixel signals to the CCU 5039 via a transmission system. The scope 5003 has an objective lens at its tip and is an insertion section that guides light from a connected light source device 5043 into the body of the patient 5071. The scope 5003 is, for example, a rigid scope if it is a rigid endoscope or a flexible scope if it is a flexible endoscope. The scope 5003 may be a direct endoscope or an oblique endoscope. Furthermore, the pixel signal may be a signal based on a signal output from a pixel, such as a RAW signal or an image signal. A configuration may also be adopted in which a memory is installed in the transmission system connecting the endoscope 5001 and the CCU 5039, and parameters related to the endoscope 5001 and the CCU 5039 are stored in the memory. The memory may be located, for example, at a connection portion of the transmission system or on a cable. For example, parameters at the time of shipment of the endoscope 5001 and parameters that change when power is applied may be stored in the memory of the transmission system, and the operation of the endoscope may be changed based on parameters read from the memory. The endoscope and the transmission system may be collectively referred to as an endoscope. The light receiving element 50054 is a sensor that converts received light into a pixel signal, and is, for example, a CMOS (Complementary Metal Oxide Semiconductor) type imaging element. It is preferable that the light receiving element 50054 be an imaging element capable of color imaging with a Bayer array. Furthermore, the light receiving element 50054 is preferably an imaging element having a number of pixels corresponding to a resolution of, for example, 4K (3840 horizontal pixels × 2160 vertical pixels), 8K (7680 horizontal pixels × 4320 vertical pixels), or square 4K (3840 or more horizontal pixels × 3840 or more vertical pixels). The light receiving element 50054 may be a single sensor chip or multiple sensor chips.For example, a prism may be provided to separate incident light into predetermined wavelength bands, and each wavelength band may be imaged by a different light-receiving element. Alternatively, multiple light-receiving elements may be provided for stereoscopic vision. The light-receiving element 50054 may be a sensor including an image processing circuit within its chip structure, or a Time of Flight (ToF) sensor. The transmission system may be, for example, an optical fiber cable or wireless transmission. Wireless transmission may be performed via any means capable of transmitting pixel signals generated by the endoscope 5001. For example, the endoscope 5001 and the CCU 5039 may be connected wirelessly, or the endoscope 5001 and the CCU 5039 may be connected via a base station in the operating room. In this case, the endoscope 5001 may simultaneously transmit not only pixel signals but also information related to the pixel signals (e.g., pixel signal processing priority, synchronization signal, etc.). The endoscope may be configured such that the scope and camera are integrated, or a light-receiving element is provided at the tip of the scope.

[0174] [CCU (Camera Control Unit)] The CCU 5039 is a control device that comprehensively controls the connected endoscope 5001 and light source device 5043, and is, for example, an information processing device having an FPGA 50391, a CPU 50392, a RAM 50393, a ROM 50394, a GPU 50395, and an I / F 50396, as shown in FIG. 21 . The CCU 5039 may also comprehensively control the connected display device 5041, recording device 5053, and output device 5055. For example, the CCU 5039 controls the irradiation timing, irradiation intensity, and type of irradiation light source of the light source device 5043. The CCU 5039 also performs image processing such as development processing (e.g., demosaic processing) and correction processing on pixel signals output from the endoscope 5001, and outputs the processed pixel signals (e.g., images) to an external device such as the display device 5041. The CCU 5039 also transmits control signals to the endoscope 5001 to control the driving of the endoscope 5001. The control signal is, for example, information regarding imaging conditions such as the magnification and focal length of the imaging unit. The CCU 5039 may have an image down-conversion function and may be configured to be able to simultaneously output a high-resolution (e.g., 4K) image to the display device 5041 and a low-resolution (e.g., HD) image to the recording device 5053.

[0175] The CCU 5039 may also be connected to external devices (e.g., recording devices, display devices, output devices, and support devices) via an IP converter that converts signals into a predetermined communication protocol (e.g., IP (Internet Protocol)). The connection between the IP converter and the external device may be configured as a wired network, or a partial or entire network may be configured as a wireless network. For example, the IP converter on the CCU 5039 side may have a wireless communication function and transmit the received video to an IP switcher or an output-side IP converter via a wireless communication network such as a fifth-generation mobile communication system (5G) or a sixth-generation mobile communication system (6G).

[0176] [Light source device] The light source device 5043 is a device capable of emitting light in a predetermined wavelength band and includes, for example, multiple light sources and a light source optical system that guides the light from the multiple light sources. The light sources are, for example, a xenon lamp, an LED light source, or an LD light source. The light source device 5043 has, for example, LED light sources corresponding to the three primary colors R, G, and B, and emits white light by controlling the output intensity and output timing of each light source. The light source device 5043 may also include a light source that can emit special light used for special light observation, in addition to a light source that emits normal light used for normal light observation. The special light is light in a predetermined wavelength band different from the normal light used for normal light observation, such as near-infrared light (light with a wavelength of 760 nm or more), infrared light, blue light, or ultraviolet light. The normal light is, for example, white light or green light. Narrowband light observation, which is a type of special light observation, alternately emits blue light and green light, allowing high-contrast imaging of specific tissues, such as blood vessels on the surface of mucous membranes, by utilizing the wavelength-dependence of light absorption in body tissue. Furthermore, in fluorescence observation, which is a type of special light observation, excitation light that excites a drug injected into body tissue is irradiated and fluorescence emitted by the body tissue or the drug as a marker is received to obtain a fluorescence image, thereby making it easier for the surgeon to visualize body tissue that is difficult for the surgeon to visualize under normal light. For example, in fluorescence observation using infrared light, infrared light having an excitation wavelength band is irradiated onto a drug such as indocyanine green (ICG) injected into body tissue, and the fluorescence of the drug is received, making it easier to visualize the structure of body tissue and affected areas. Furthermore, in fluorescence observation, a drug (e.g., 5-ALA) that is excited by special light in the blue wavelength band and emits fluorescence in the red wavelength band may be used. The type of irradiated light for the light source device 5043 is set under the control of the CCU 5039. The CCU 5039 may have a mode in which normal light observation and special light observation are alternately performed by controlling the light source device 5043 and the endoscope 5001. In this case, it is preferable that information based on pixel signals obtained under special light observation be superimposed on pixel signals obtained under normal light observation. The special light observation may be infrared observation, which uses infrared light to see deeper than the surface of an organ, or multispectral observation using hyperspectral spectroscopy. Photodynamic therapy may also be combined.

[0177] [Recording Device] The recording device 5053 is a device, such as a recorder, that records pixel signals (e.g., images) acquired from the CCU 5039. The recording device 5053 records images acquired from the CCU 5039 on a HDD, an SDD, or an optical disk. The recording device 5053 may be connected to a network within the hospital so as to be accessible from devices outside the operating room. The recording device 5053 may also have an image down-conversion or up-conversion function.

[0178] [Display device] The display device 5041 is a device capable of displaying an image, such as a display monitor. The display device 5041 displays an image based on pixel signals acquired from the CCU 5039. The display device 5041 may also function as an input device that enables gaze recognition, voice recognition, and instruction input using gestures by including a camera and a microphone.

[0179] [Output device] The output device 5055 is a device, such as a printer, that outputs information acquired from the CCU 5039. The output device 5055 prints, for example, a print image based on the pixel signal acquired from the CCU 5039 onto paper.

[0180] [Support device] The support device 5027 is an articulated arm including a base 5029 having an arm control device 5045, an arm 5031 extending from the base 5029, and a holder 5032 attached to the tip of the arm 5031. The arm control device 5045 is configured with a processor such as a CPU and controls the drive of the arm 5031 by operating according to a predetermined program. The support device 5027 controls the position and posture of the endoscope 5001 held by the holder 5032, for example, by controlling parameters such as the length of each link 5035 constituting the arm 5031 and the rotation angle and torque of each joint 5033 using the arm control device 5045. This allows the endoscope 5001 to be changed to a desired position or posture, allowing the scope 5003 to be inserted into the patient 5071 and the observation area within the body to be changed. The support device 5027 functions as an endoscope support arm that supports the endoscope 5001 during surgery. This allows the support device 5027 to take the place of an assistant scopist who holds the endoscope 5001. The support device 5027 may also be a device that supports a microscope device 5301 (described later) and may also be called a medical support arm. The support device 5027 may be controlled autonomously by the arm control device 5045, or may be controlled by the arm control device 5045 based on user input. For example, the control method may be a master-slave method in which the support device 5027, which serves as a slave device (replica device) serving as a patient cart, is controlled based on the movement of a master device (primary device) that is an operator console located at the user's hand. The support device 5027 may also be remotely controlled from outside the operating room.

[0181] The above describes an example of the endoscope system 5000 to which the technology according to the present disclosure can be applied. For example, the technology according to the present disclosure may be applied to a microscope system.

[0182] [Microscope system] 22 is a diagram showing an example of a schematic configuration of a microsurgical system to which the technology according to the present disclosure can be applied. In the following description, components similar to those in the endoscope system 5000 are assigned the same reference numerals, and redundant description thereof will be omitted.

[0183] 22 shows a schematic diagram of an operator 5067 performing surgery on a patient 5071 on a patient bed 5069 using a microsurgical system 5300. For simplicity, the illustration of the cart 5037 of the microsurgical system 5300 is omitted, and the illustration of the microscope device 5301 that replaces the endoscope 5001 is simplified. However, the microscope device 5301 in this description may refer to the microscope unit 5303 provided at the tip of the link 5035, or may refer to the entire configuration including the microscope unit 5303 and the support device 5027.

[0184] 22, during surgery, a microsurgical system 5300 is used to display an enlarged image of the surgical site captured by a microscope device 5301 on a display device 5041 installed in an operating room. The display device 5041 is installed in a position facing an operator 5067, who performs various procedures on the surgical site, such as resecting the affected area, while observing the state of the surgical site using the image displayed on the display device 5041. Microsurgical systems are used, for example, in ophthalmic surgery and brain surgery.

[0185] The above describes examples of an endoscopic system 5000 and a microsurgery system 5300 to which the technology of the present disclosure can be applied. Note that the systems to which the technology of the present disclosure can be applied are not limited to these examples. For example, the support device 5027 may support another observation device or another surgical tool at its tip instead of the endoscope 5001 or the microscope unit 5303. Examples of such other observation devices include forceps, a surgeon, an insufflation tube for insufflation, or an energy treatment tool for incising tissue or sealing blood vessels by cauterization. Supporting these observation devices and surgical tools with a support device allows them to be more stably fixed in position than when medical staff support them manually, and also reduces the burden on medical staff. The technology of the present disclosure may be applied to support devices that support components other than the microscope unit.

[0186] Of the configurations described above, the technology according to the present disclosure can be suitably applied to the surgical tool 5021. Specifically, by irradiating the affected area of ​​a patient with a short laser pulse from the laser element 1 according to this embodiment, the affected area can be treated more safely and reliably without causing damage to the area around the affected area.

[0187] The present technology can be configured as follows: (1) a laminated semiconductor layer having a first reflective layer for a first wavelength and an active layer for surface emitting light of the first wavelength; a laser medium disposed on the rear side of the optical axis of the laminated semiconductor layer, the laser medium having a second reflective layer for a second wavelength on a first surface facing the laminated semiconductor layer and a third reflective layer for the first wavelength on a second surface opposite to the first surface; a fourth reflective layer for the second wavelength, which is disposed on the second surface or on a rear side of the second surface along the optical axis; a first resonator that resonates light of the first wavelength between the first reflective layer and the third reflective layer; a second resonator that resonates light of the second wavelength between the second reflective layer and the fourth reflective layer; a heat dissipation unit disposed between the laminated semiconductor layer and the laser medium, for dissipating heat generated by at least one of the laminated semiconductor layer and the laser medium; A laser element, wherein the optical axis of the laminated semiconductor layer and the optical axis of the laser medium are arranged on the same axis. (2) The laser element according to (1), wherein the heat dissipation section is disposed between the laminated semiconductor layer and the laser medium and has a first member having a higher thermal conductivity than the laser medium. (3) A laser element according to (2), comprising a metal layer disposed on part or all of the surface of the first member facing the laser medium, the metal layer having a higher thermal conductivity than the laminated semiconductor layer and the laser medium. (4) A laser element according to (2) or (3), comprising a second member bonded to the side surfaces of the laminated semiconductor layer, the side surfaces of the first member, and the side surfaces of the laser medium, and configured to dissipate heat transferred to the first member. (5) a substrate supporting the laminated semiconductor layer; a bonding wire connected to a pad on the substrate and an electrode of the laminated semiconductor layer; The laser element according to (4), wherein the second member is arranged to cover the side surfaces of the laminated semiconductor layer and the laser medium, and the bonding wire. (6) The first member includes at least one of sapphire and diamond, The laser element according to (4) or (5), wherein the second member includes a metal material. (7) A laser element according to any one of (2) to (6), comprising a protective layer disposed on the surface of the first member opposite the laminated semiconductor layer, the protective layer transmitting light of the first wavelength and reflecting light of the second wavelength. (8) A laser element described in any one of (1) to (7), wherein the first member has a first region that transmits light of the first wavelength and a second region that is arranged around the first region and has a higher thermal conductivity than the laser medium. (9) The laser element according to (8), wherein the second region is made of an insulating material or a metallic material. (10) The second region is disposed so as to surround the first region, The laser element according to (8) or (9), wherein the outer peripheral surface of the second region or the corners of the outer peripheral surface are positioned equidistant from the center position of the first region. (11) A plurality of the first resonators and a plurality of the second resonators are provided in a plane direction of the laminated semiconductor layer, the heat dissipation portion, and the laser medium. A laser element according to any one of (1) to (10). (12) The laser element according to (1), wherein the heat dissipation section has an air gap disposed between the laminated semiconductor layer and the laser medium. (13) The laser element according to any one of (1) to (12), further comprising a first optical element disposed between the second reflective layer to the fourth reflective layer and expanding the beam diameter of the light of the second wavelength. (14) The laser element according to any one of (1) to (13), wherein the first resonator has a second optical element that focuses the light of the first wavelength in an optical axis direction. (15) A saturable absorber having the fourth reflecting layer on a third surface opposite to the laser medium, The laser element according to any one of (1) to (14), wherein the optical axis of the laminated semiconductor layer, the optical axis of the laser medium, and the optical axis of the saturable absorber are arranged on a single axis. (16) The laser element according to (15), wherein the laminated semiconductor layer, the laser medium, and the saturable absorber are integrally bonded together. (17) The laser element according to (15) or (16), further comprising a polarization control element that is arranged between the laser medium and the saturable absorber or on the rear side of the saturable absorber on the optical axis, and that controls the polarization state of the light of the second wavelength. (18) The laser device according to claim 1, wherein the fourth reflective layer is an output coupling mirror in the second resonator. (19) The laminated semiconductor layer includes a fifth reflective layer for the first wavelength, the fifth reflective layer being disposed closer to the laser medium than the first reflective layer; 2. The laser device according to claim 1, wherein the fifth reflective layer transmits a portion of the light of the first wavelength. (20) A laser element; a control unit that controls the emission of light from the laser element, The laser element is a laminated semiconductor layer having a first reflective layer for a first wavelength and an active layer for surface emitting light of the first wavelength; a laser medium disposed on the rear side of the optical axis of the laminated semiconductor layer, the laser medium having a second reflective layer for a second wavelength on a first surface facing the laminated semiconductor layer and a third reflective layer for the first wavelength on a second surface opposite to the first surface; a fourth reflective layer for the second wavelength, which is disposed on the second surface or on a rear side of the second surface along the optical axis; a first resonator that resonates light of the first wavelength between the first reflective layer and the third reflective layer; a second resonator that resonates light of the second wavelength between the second reflective layer and the fourth reflective layer; a heat dissipation unit disposed between the laminated semiconductor layer and the laser medium, for dissipating heat generated by at least one of the laminated semiconductor layer and the laser medium; an optical axis of the laminated semiconductor layer and an optical axis of the laser medium are arranged on a single axis; (21) A laminated semiconductor layer having a first reflective layer for a first wavelength and an active layer that performs surface emission of the first wavelength; a laser medium disposed on the rear side of the laminated semiconductor layer with respect to the optical axis, the laser medium having a second reflective layer for the first wavelength on a second surface opposite to a first surface facing the laminated semiconductor layer; a first reflecting member and a second reflecting member disposed along a first side surface and a second side surface facing each other of the laser medium; a light input portion provided along the first side surface and configured to input light of a second wavelength; an optical output section provided along the second side surface, which amplifies and outputs the light of the second wavelength; a first resonator that resonates light of the first wavelength between the first reflective layer and the second reflective layer, the laser medium is an amplifying medium that causes the light of the second wavelength to travel back and forth between the first reflecting member and the second reflecting member a plurality of times, The optical axis of the laminated semiconductor layer and the optical axis of the laser medium are arranged on the same axis. (22) The laser amplification element according to (21), wherein, in a state where the laser medium is excited by the resonant operation of the light of the first wavelength by the first resonator, light of the second wavelength is input from the light input unit, the light of the second wavelength travels back and forth multiple times in the amplification medium, and then the light of the second wavelength is amplified and output from the light output unit. (23) A first heat dissipation member is disposed between the laminated semiconductor layer and the laser medium, and dissipates heat generated by at least one of the laminated semiconductor layer and the laser medium; The laser amplification element according to (21) or (22), wherein the optical axis of the laminated semiconductor layer, the optical axis of the first heat discharging member, and the optical axis of the laser medium are arranged on a single axis. (24) The laser amplification element according to (23), wherein the thermal conductivity of the first heat discharging member is higher than the thermal conductivity of the laser medium. (25) The laser amplification element according to (23) or (24), further comprising a second heat dissipation member bonded to an end face of the laser medium opposite to an end face facing the laminated semiconductor layer, and configured to dissipate heat generated in the laser medium. (26) The laser amplification element according to (25), wherein the thermal conductivity of the second heat discharging member is higher than the thermal conductivity of the laser medium. (27) A laser amplification element according to any one of (23) to (26), comprising a cooling member bonded to the side surfaces of the laminated semiconductor layer, the first heat dissipation member, and the laser medium, and configured to dissipate heat transferred from at least one of the laminated semiconductor layer and the laser medium to the first heat dissipation member. (28) The first heat exhaust member has a plurality of via members that penetrate the first heat exhaust member and are joined to the laminated semiconductor and the laser medium, The laser amplification element according to any one of (23) to (27), wherein the thermal conductivity of the plurality of via members is higher than the thermal conductivity of the first heat dissipation member. (29) A laser amplification element according to any one of (21) to (28), wherein the first reflecting member and the second reflecting member are convex mirror members that reflect incident light so as not to be focused. (30) A laser amplification element described in any one of (21) to (29), wherein the first reflecting member and the second reflecting member are multilayer films formed by stacking at least one of a semiconductor material, a metal material, and a dielectric material and arranged on the first side surface and the second side surface.

[0188] The aspects of the present disclosure are not limited to the individual embodiments described above, but include various modifications that may be conceived by those skilled in the art, and the effects of the present disclosure are not limited to the above-described contents. In other words, various additions, modifications, and partial deletions are possible within the scope of the conceptual idea and spirit of the present disclosure, which is derived from the contents defined in the claims and their equivalents. [Explanation of symbols]

[0189] 1 laser element, 2 laminated semiconductor layer (pumping light source), 3 solid-state laser medium, 4 saturable absorber, 5 n-GaAs substrate, 6 cladding layer, 7 active layer, 8 cladding layer, 9 optical element, 11 first resonator, 12 second resonator, 13 heat dissipation section, 13a first region, 13b second region, 14 cooling member (second member), 16 bonding wire, 17 heat dissipation member (first member), 17 heat dissipation member, 18 metal layer, 19 first protective layer, 20 second protective layer, 21 resist film, 22 photomask, 23 recess, 24 dielectric multilayer film, 25 alignment mark, 26 camera, 27 first transparent medium, 28 second transparent medium, 29 transparent member, 31 contact layer, 32 oxide layer (e.g., Al2O3 layer), 33 contact layer, 34 insulating film, 35 Conductive material, 41 optical element, 42 convex mirror, 43 light control member, 44 laser array, 45 transparent substrate, 50 laser amplifier element, 51 support substrate, 52 submount substrate, 53 pumping light source, 54 solid-state laser medium, 54S1 first side surface, 54S1 side surface, 54S2 second side surface, 55 first resonator, 56 first reflecting member, 57 second reflecting member, 58 second resonator, 60 first heat dissipation member, 61 second heat dissipation member, 62 cooling member, 64 SiC layer, 65 AuSn layer, 66 n-GaAs substrate, 67 contact layer, 69 cladding layer, 70 active layer, 71 cladding layer, 73 p-electrode, 74 n-electrode, 75 via, 76 via member, 81 pumping light source, 82 pumping light source, 83 amplifying medium, 84 polarizer, 85 λ / 4 plate, 86 laser array, 87 waveguide, 91 submount substrate, 92 support substrate

Claims

1. a laminated semiconductor layer including a first reflective layer for a first wavelength and an active layer for surface emitting light of the first wavelength; a laser medium disposed on the rear side of the laminated semiconductor layer with respect to the optical axis, the laser medium having a second reflective layer for a second wavelength on a first surface facing the laminated semiconductor layer and a third reflective layer for the first wavelength on a second surface opposite to the first surface; a fourth reflective layer for the second wavelength, the fourth reflective layer being disposed on the second surface or on a rear side of the second surface along the optical axis; a first resonator that resonates light of the first wavelength between the first reflective layer and the third reflective layer; a second resonator that resonates light of the second wavelength between the second reflective layer and the fourth reflective layer; a heat dissipation unit disposed between the laminated semiconductor layer and the laser medium, configured to dissipate heat generated by at least one of the laminated semiconductor layer and the laser medium, and having a first member; a metal layer; an optical axis of the laminated semiconductor layer and an optical axis of the laser medium are arranged on a single axis; the first member is disposed between the laminated semiconductor layer and the laser medium and has a thermal conductivity higher than that of the laser medium; the metal layer is disposed on a part or all of a surface of the first member facing the laser medium, and has a thermal conductivity higher than that of the laminated semiconductor layer and the laser medium; Laser element.

2. a laminated semiconductor layer including a first reflective layer for a first wavelength and an active layer for surface emitting light of the first wavelength; a laser medium disposed on the rear side of the laminated semiconductor layer with respect to the optical axis, the laser medium having a second reflective layer for a second wavelength on a first surface facing the laminated semiconductor layer and a third reflective layer for the first wavelength on a second surface opposite to the first surface; a fourth reflective layer for the second wavelength, the fourth reflective layer being disposed on the second surface or on a rear side of the second surface along the optical axis; a first resonator that resonates light of the first wavelength between the first reflective layer and the third reflective layer; a second resonator that resonates light of the second wavelength between the second reflective layer and the fourth reflective layer; a heat dissipation unit disposed between the laminated semiconductor layer and the laser medium, configured to dissipate heat generated by at least one of the laminated semiconductor layer and the laser medium, and having a first member; an optical axis of the laminated semiconductor layer and an optical axis of the laser medium are arranged on a single axis; the first member has a first region that transmits light of the first wavelength, and a second region that is disposed around the first region and has a thermal conductivity higher than that of the laser medium, the first member is disposed between the laminated semiconductor layer and the laser medium; Laser element.

3. the second region is an insulating material or a metallic material; The laser device according to claim 2 .

4. the second region is disposed so as to surround the first region, The outer peripheral surface of the second region or the corners of the outer peripheral surface are positioned equidistant from the center position of the first region.

4. The laser device according to claim 2 or 3.

5. a laminated semiconductor layer including a first reflective layer for a first wavelength and an active layer for surface emitting light of the first wavelength; a laser medium disposed on the rear side of the laminated semiconductor layer with respect to the optical axis, the laser medium having a second reflective layer for a second wavelength on a first surface facing the laminated semiconductor layer and a third reflective layer for the first wavelength on a second surface opposite to the first surface; a fourth reflective layer for the second wavelength, the fourth reflective layer being disposed on the second surface or on a rear side of the second surface along the optical axis; a first resonator that resonates light of the first wavelength between the first reflective layer and the third reflective layer; a second resonator that resonates light of the second wavelength between the second reflective layer and the fourth reflective layer; a heat dissipation unit disposed between the laminated semiconductor layer and the laser medium, for dissipating heat generated by at least one of the laminated semiconductor layer and the laser medium; a first optical element disposed between the second reflective layer to the fourth reflective layer and expanding a beam diameter of the light of the second wavelength, the optical axis of the laminated semiconductor layer and the optical axis of the laser medium are arranged on the same axis. Laser element.

6. the heat dissipation unit has an air gap disposed between the laminated semiconductor layer and the laser medium. The laser device according to claim 5 .

7. the heat dissipation unit is disposed between the laminated semiconductor layer and the laser medium and includes a first member having a thermal conductivity higher than that of the laser medium. The laser device according to claim 5 .

8. a metal layer disposed on a part or all of the surface of the first member facing the laser medium, the metal layer having a thermal conductivity higher than that of the laminated semiconductor layer and the laser medium; 8. The laser device according to claim 2, wherein the first and second electrodes are arranged parallel to each other.

9. a second member bonded to a side surface of the laminated semiconductor layer, a side surface of the first member, and a side surface of the laser medium, and configured to dissipate heat transferred to the first member; 9. The laser device according to claim 1, 2, 3, 4, 5, 6, 7, or 8.

10. a laminated semiconductor layer including a first reflective layer for a first wavelength and an active layer for surface emitting light of the first wavelength; a laser medium disposed on the rear side of the laminated semiconductor layer with respect to the optical axis, the laser medium having a second reflective layer for a second wavelength on a first surface facing the laminated semiconductor layer and a third reflective layer for the first wavelength on a second surface opposite to the first surface; a fourth reflective layer for the second wavelength, the fourth reflective layer being disposed on the second surface or on a rear side of the second surface along the optical axis; a first resonator that resonates light of the first wavelength between the first reflective layer and the third reflective layer; a second resonator that resonates light of the second wavelength between the second reflective layer and the fourth reflective layer; a heat dissipation unit disposed between the laminated semiconductor layer and the laser medium, configured to dissipate heat generated by at least one of the laminated semiconductor layer and the laser medium, and having a first member; a second member bonded to a side surface of the laminated semiconductor layer, a side surface of the first member, and a side surface of the laser medium, and configured to radiate heat transferred to the first member; the first member is disposed between the laminated semiconductor layer and the laser medium and has a thermal conductivity higher than that of the laser medium; the optical axis of the laminated semiconductor layer and the optical axis of the laser medium are arranged on the same axis. Laser element.

11. a substrate supporting the laminated semiconductor layer; a bonding wire connected to a pad on the substrate and an electrode of the laminated semiconductor layer; the second member is disposed so as to cover the side surfaces of the laminated semiconductor layer and the laser medium, and the bonding wire; 11. The laser device according to claim 9 or 10.

12. the first member includes at least one of sapphire and diamond; The second member includes a metal material.

12. The laser device according to claim 9.

13. a protective layer disposed on a surface of the first member facing the laminated semiconductor layer, the protective layer transmitting light of the first wavelength and reflecting light of the second wavelength; 13. The laser device according to claim 1, wherein the first and second electrodes are arranged parallel to each other.

14. a plurality of the first resonators and a plurality of the second resonators are provided in a plane direction of the laminated semiconductor layer, the heat dissipation portion, and the laser medium; 14. A laser device according to any one of claims 1 to 13.

15. a first optical element disposed between the second reflective layer to the fourth reflective layer and expanding the beam diameter of the light of the second wavelength; 15. A laser device according to any one of claims 1 to 14.

16. the first resonator has a second optical element that focuses the light of the first wavelength in an optical axis direction; 16. A laser device according to any one of claims 1 to 15.

17. a saturable absorber having the fourth reflecting layer on a third surface opposite to the laser medium; an optical axis of the laminated semiconductor layer, an optical axis of the laser medium, and an optical axis of the saturable absorber are arranged on a single axis; 17. A laser device according to any one of claims 1 to 16.

18. the laminated semiconductor layer, the laser medium, and the saturable absorber are integrally bonded together; 18. The laser device according to claim 17.

19. a polarization control element disposed between the laser medium and the saturable absorber or on the rear side of the saturable absorber along the optical axis, the polarization control element controlling the polarization state of the light of the second wavelength; 19. The laser device according to claim 17 or 18.

20. A laser device according to any one of claims 1 to 19; A control unit that controls the emission of light from the laser element. electronic equipment.

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