Laser elements and electronic devices

Abstract

[Problem] To suppress diffraction loss during laser resonance. [Solution] This laser element comprises: a laminated semiconductor layer that has a first reflection layer for a first wavelength and an active layer that performs surface emission of the first wavelength; a laser medium that is disposed on the rear side of an optical axis of the laminated semiconductor layer, and that has a second reflection layer for a second wavelength on a first plane facing the laminated semiconductor layer, and a third reflection layer for the first wavelength on a second plane that is on the opposite side of the first plane; a fourth reflection layer for the second wavelength and disposed on the second plane or further to the rear side of the optical axis than the second plane; a first resonator that causes the light of the first wavelength to resonate between the first reflection layer and the third reflection layer; and a second resonator that causes the light of the second wavelength to resonate between the second reflection layer and the fourth reflection layer. The first resonator has an optical element that condenses the light of the first wavelength in the optical axis direction, and the optical axis of the laminated semiconductor layer, the optical axis of the laser medium, and the optical axis of the optical element are disposed on the same axis.

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] One way to shorten the pulse width of laser light is to share a cavity between the pump laser and the Q-switched solid-state laser. In this case, the cavity length can be shortened on the Q-switched solid-state laser side, but the cavity length on the pump laser side becomes longer because the solid-state laser medium is also involved in the resonation. As the cavity length increases, diffraction loss generally increases, which reduces the light density inside the semiconductor cavity. In other words, if the cavity length on the surface-emitting laser side increases, the pump light density in the solid-state laser medium will decrease. This reduces the output power of the solid-state laser.

[0010] Therefore, the present disclosure provides a laser element and an electronic device that can suppress diffraction loss during laser resonance. [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, the first resonator has an optical element that focuses the light of the first wavelength in an optical axis direction; There is provided a laser element in which the optical axis of the laminated semiconductor layer, the optical axis of the laser medium, and the optical axis of the optical element are arranged on a single axis.

[0012] The optical element may comprise a concave mirror.

[0013] The concave mirror may have a multilayer structure in which at least one of a semiconductor material, a metal material, and a dielectric material is laminated.

[0014] At least one of the first reflective layer and the third reflective layer may include the concave mirror.

[0015] the laminated semiconductor layer includes a first semiconductor layer having a concave end face on the first reflective layer side, The concave mirror may be laminated on the first semiconductor layer.

[0016] the laser medium has a concave end face on the third reflective layer side, The concave mirror may be laminated on the end surface of the laser medium.

[0017] The optical element may be bonded to an end face of the laser medium opposite to the side facing the laminated semiconductor layer.

[0018] the optical element has a first transparent material layer that transmits light of the second wavelength; a first end surface of the first transparent material layer bonded to the laser medium is a flat surface, and a second end surface opposite to the first end surface is a concave surface; The concave mirror may be disposed along the second end surface.

[0019] a second transparent material layer bonded to the second end surface of the first transparent material layer and transmitting light of the second wavelength; The end face of the second transparent material layer opposite to the bonding surface with the first transparent material layer may be a flat surface.

[0020] The optical element may include a light refracting member that refracts incident light in the direction of the optical axis.

[0021] the laminated semiconductor layer has a fifth reflective layer that is disposed closer to the laser medium than the active layer and transmits a part of the light of the first wavelength; The light refracting member may be disposed between the fifth reflective layer and the second reflective layer.

[0022] The light refracting member may have a convex end face on the side of the laminated semiconductor layer facing the laser medium.

[0023] the optical element is bonded to an end face of the laminated semiconductor layer facing the laser medium, The light refracting member may have one end face of a convex shape on the side of the optical element facing the laser medium.

[0024] the optical element has a transparent material layer bonded to the light refracting member and transmitting light of the first wavelength; the transparent material layer has a refractive index smaller than that of the light refracting member, The surface of the transparent material layer that is bonded to the light refracting member may be concave, and the end surface opposite to the bonded surface may be flat, and the end surface of the laser medium may be bonded to the flat surface.

[0025] The light refracting member may have a convex end face on a side of the laser medium facing the laminated semiconductor layer.

[0026] The second reflective layer may be disposed along an end face of the convex shape.

[0027] the optical element has a transparent material layer bonded to the light refracting member and transmitting light of the first wavelength; The surface of the transparent material layer that is bonded to the light refracting member may be concave, and the end surface opposite to the bonded surface may be flat, and the end surface of the laminated semiconductor layer may be bonded to the flat surface.

[0028] a part of the semiconductor layer including the active layer in the laminated semiconductor layer is divided into a plurality of divided regions by an insulator, Each of the plurality of divided regions may include the first resonator and the second resonator.

[0029] 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, an optical axis of the saturable absorber, and an optical axis of the optical element are arranged on a single axis; The laminated semiconductor layer, the laser medium, and the saturable absorber may be integrally bonded together.

[0030] According to another aspect of 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, the first resonator has an optical element that focuses the light of the first wavelength in an optical axis direction; The electronic device is provided, in which the optical axis of the laminated semiconductor layer, the optical axis of the laser medium, and the optical axis of the optical element are arranged on a single 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 cross-sectional view of a laser device according to a first specific example. [Figure 3] FIG. 10 is a cross-sectional view of a laser device according to a second specific example. [Figure 4] FIG. 10 is a cross-sectional view of a laser device according to a third specific example. [Figure 5] FIG. 10 is a cross-sectional view of a laser device according to a fourth specific example. [Figure 6] FIG. 10 is a cross-sectional view of a laser device according to a fifth example. [Figure 7] 10 is a cross-sectional view of a laser device according to a sixth example. [Figure 8] FIG. 13 is a cross-sectional view of a laser device according to a seventh example. [Figure 9] FIG. 13 is a cross-sectional view of a laser device according to an eighth example. [Figure 10] FIG. 13 is a cross-sectional view of a laser device according to a ninth example. [Figure 11] 3A to 3C are diagrams schematically illustrating a manufacturing process for a laser element according to the present disclosure. [Figure 12] 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 13] FIG. 1 is a diagram showing the basic configuration of a laser element that does not have a saturable absorber. [Figure 14] FIG. 1 is a diagram showing an example of a schematic configuration of an endoscope system. [Figure 15] FIG. 15 is a block diagram showing an example of the functional configuration of the camera and the CCU shown in FIG. 14. [Figure 16] 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] In the laser element according to the present disclosure, the first wavelength light is resonated between the laminated semiconductor layer and the solid-state laser medium, so the cavity length is longer than when the light is resonated only in the laminated semiconductor layer. As a result, as described above, the diffraction loss increases and the excitation light density in the solid-state laser medium decreases. Therefore, the laser element according to the present disclosure is provided with an optical element to suppress the diffraction loss.

[0040] 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.

[0041] (2) The first resonator has an optical element inside that focuses light of the first wavelength in the optical axis direction. This optical element has, for example, a concave mirror. The concave mirror is at least one of the first reflective layer and the third reflective layer provided on both sides of the first resonator. Alternatively, the optical element has, for example, a light refracting member. The light refracting member refracts incident light in the optical axis direction. The light refracting member is provided between a fifth reflective layer (sometimes called an intermediate mirror) in the laminated semiconductor layer and the second reflective surface of the laser medium.

[0042] (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.

[0043] (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.

[0044] 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.

[0045] 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.

[0046] The active layer 7 emits light of the first wavelength λ1 from a surface. The cladding layers 6 and 8 are, for example, undoped 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.

[0047] The first reflective layer R1 and the fifth reflective layer R5 are, for example, electrically conductive semiconductor distributed Bragg reflectors (DBRs). In the case of FIG. 1, the first reflective layer R1 is a p-DBR, and the fifth reflective layer R5 is an n-DBR. The p-DBR and n-DBR are each multi-layer reflective layers in which low refractive index layers and high refractive index layers are alternately stacked. The p-DBR and n-DBR are doped with the corresponding dopant (e.g., carbon for the p-DBR, and silicon for the n-DBR). More specifically, the p-DBR and n-DBR are doped with Al z1 Ga 1-z1 As / Al Z2 Ga 1-z2The fifth reflective layer R5 is made of As (0≦z1≦z2≦1). In order to distinguish it from an oxide layer, which will be described later, it is preferable that z2 is not 1. An n-contact layer 33 is disposed between the fifth reflective layer R5 and the n-GaAs substrate 5.

[0048] 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 (e.g., AlAs layer) 31 on the cladding layer side of the first reflective layer R1 is removed by dry etching or the like, and oxidized and altered to become a post-oxidation layer (e.g., Al2O3 layer) 32. This makes it possible to electrically and optically confine light of the first wavelength.

[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 In more detail, the active layer 7 includes quantum well layers and barrier layers alternately stacked to have compressive strain. x1 In y1 Ga 1-x1-y1 As layer and Al x3 In y3 Ga 1-x3-y3 It is formed of an As layer. It may also have a multi-junction structure via a tunnel junction.

[0050] 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, thereby enabling driving by current injection. Note that the layered structure (layered semiconductor layers) of the excitation light source 2 shown in FIG. 1 is an example, and the material, layer configuration, and semiconductor process used in manufacturing each semiconductor layer are not limited to those described above.

[0051] 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.

[0052] The laser device 1 in Fig. 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. The conductivity type of the laminated semiconductor layer 2 may be opposite to that described above, and the substrate 5 may be a non-doped substrate.

[0053] 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.

[0054] 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.

[0055] The power of the pump light of the first wavelength λ1 is confined within the first resonator 11, thereby exciting the solid-state laser medium 3. 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 optical axis from the laser pulse exit surface of the saturable absorber 4. "Behind the optical axis" refers to the direction in which the 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. However, even if the fourth reflective layer R4 is disposed further forward on the optical axis than the saturable absorber 4, it is necessary to resonate the light of the second wavelength λ2 between the second reflective layer R2 and the fourth reflective layer R4.

[0056] 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.

[0057] The solid-state laser medium 3 is not limited to Yb:YAG, and for example, at least one of the following materials can be used for the solid-state laser medium 3: 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] To firmly bond the solid-state laser medium 3 to the pumping light source 2, it is necessary to flatten the surface of the n-GaAs substrate 5 within the pumping light source 2. Therefore, as described above, it is desirable to arrange the electrodes E1 and E2 for injecting current into the first reflective layer R1 and the fifth reflective layer R5 so that they are not exposed at least on the surface of the n-GaAs substrate 5. In the example shown in FIG. 1 , the electrodes E1 and E2 are arranged on the end face of the pumping light source 2 on the first reflective layer R1 side. The electrode E1 is a p-electrode and is electrically connected to the first reflective layer R1. The electrode E2 is an n-electrode and is formed by filling the side 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, and bringing the electrode E2 into contact with the n-contact layer 33. By arranging the 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, by arranging electrodes E1 and E2 on the same end surface, this end surface can be mounted on a support substrate. Note that the shapes and locations of electrodes E1 and E2 shown in Figure 1 are merely examples.

[0062] 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.

[0063] 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 .

[0064] 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.

[0065] Dielectric multilayer films include short-wavelength transmission filter films (SWPF: Short Wave Pass Filter), long-wavelength transmission filter films (LWPF: Long Wave Pass Filter), band-pass filter films (BPF: Band Pass Filter), and anti-reflection protective films (AR: Anti-Reflection). 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 by vacuum deposition, ion-assisted deposition, sputtering, or other 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.

[0066] 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 polarization and S polarization 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.

[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 basic configuration and operating principle for obtaining Q-switched laser oscillation according to the present disclosure have been described above. However, as mentioned at the beginning, the configuration of the laser element in FIG. 1 cannot solve the problem that the long resonator length of the first resonator 11 causes large diffraction loss, limiting the laser output.

[0072] (Measures to reduce diffraction loss) First, we will explain why the diffraction loss increases as the cavity length of the first cavity 11 increases. Here, the diffraction loss occurs due to the presence of light that is emitted from the active layer 7 and that is emitted outside the first cavity 11 while resonating within the first cavity 11. If this emitted light can be kept within the cavity, the loss can be reduced. It is known that a cavity that uses a concave mirror as the reflecting mirror of the cavity can reduce diffraction loss more effectively than a parallel plate mirror, but no specific method has been proposed for suppressing the diffraction loss of one of the cavities in a configuration in which two cavities share a solid-state laser medium.

[0073] A specific configuration of a laser element for suppressing diffraction loss in the first resonator 11 will be described below. The laser element according to the present disclosure includes an optical element in addition to the basic structure shown in FIG. 1. The optical element is provided in the first resonator 11. The optical element has a function of focusing light of the first wavelength in the optical axis direction. Since multiple specific configurations of the optical element are possible, laser elements including optical elements with different configurations will be described below in order.

[0074] (First Example of Laser Element) Fig. 2 is a cross-sectional view of a laser device 1 according to a first specific example. Similar to Fig. 1, the laser device 1 in Fig. 2 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. In the laser device 1 in Fig. 2, the electrodes E1 and E2 shown in Fig. 1 are omitted.

[0075] The laser device 1 in FIG. 2 includes an optical element 9. The optical element 9 in FIG. 2 includes a concave mirror 10. The concave mirror 10 in FIG. 2 is a concave-shaped first reflective layer R1 included in the pumping light source 2. The optical element 9 in FIG. 2 is obtained by processing the first reflective layer R1 of the pumping light source 2 into a concave shape. As described above, the first resonator 11 resonates light of the first wavelength λ1 between the first reflective layer R1 provided on the end face of the pumping light source 2 and the third reflective layer R3 provided on the end face of the solid-state laser medium 3. By providing the first reflective layer R1 with a concave shape, the light of the first wavelength λ1 reflected by the first reflective layer R1 travels in a direction focused along the optical axis of the first resonator 11, as shown by the dashed-dotted line in FIG. 2. This reduces the proportion of light that exits the first resonator 11, thereby suppressing diffraction loss.

[0076] The laser device 1 in FIG. 2 is a bottom-emission type. An n-contact layer 33, a fifth reflective layer R5, a cladding layer 6, an active layer 7, a cladding layer 8, and a concave mirror-forming layer 41 are sequentially stacked on a substrate 5. The surface of the concave mirror-forming layer 41 is processed into a convex shape by dry etching or the like, and a concave mirror 10 consisting of a multilayer film 42 stacked with at least one of a semiconductor material, a metal material, and a dielectric material is disposed on the resulting convex surface by vapor deposition, sputtering, or the like. Because the multilayer film 42 has a concave shape when viewed from inside the first resonator 11, it is referred to as the concave mirror 10 in this specification. The concave mirror-forming layer 41 may be made of any transparent material that transmits light of the first wavelength λ1, and any specific material is acceptable. The concave mirror 10 is a first reflective layer R1 that reflects light of the first wavelength λ1 in a direction that focuses the light along the optical axis of the first resonator 11.

[0077] In this way, the laser device 1 of FIG. 2 is obtained by processing the first reflective layer R1 of FIG. 1 into a convex shape, and can suppress diffraction loss without adding a new member.

[0078] (Second specific example of laser element 1) FIG. 3 is a cross-sectional view of a laser device 1 according to a second example. The laser device 1 of FIG. 3 also includes an optical element 9 consisting of a concave mirror 10. The laser device 1 of FIG. 3 is a top-emission type. In a top-emission type, the substrate 5 of the pump light source 2 is disposed on the opposite side from the solid-state laser medium 3, and the DBR on the substrate 5 side essentially corresponds to the first reflective layer R1, which is the resonator mirror of the first resonator 11. In FIG. 3, the DBR on the substrate 5 side is removed, the surface of the substrate 5 is processed to have a convex shape by dry etching or the like, and a multilayer film 42 corresponding to the pump wavelength is formed on the convex surface by vapor deposition, sputtering, or the like, thereby forming a concave mirror 10 when viewed from the resonator. This concave mirror 10 is the first reflective layer R1 that reflects light of the first wavelength λ1 in a direction that focuses the light in the optical axis direction.

[0079] In this way, the laser device 1 of FIG. 3 has the end face of the top-emission type substrate 5 processed to have a convex surface to form the concave mirror 10, so that diffraction loss can be suppressed without adding any new member.

[0080] (Third specific example of laser element 1) Fig. 4 is a cross-sectional view of a laser device 1 according to a third specific example. The laser device 1 of Fig. 4 includes an optical element 9 on the saturable absorber 4 side of the solid-state laser medium 3. This optical element 9 has a concave mirror 10. This concave mirror 10 functions as a third reflective layer R3. Light of the first wavelength λ1 incident on this concave mirror 10 is reflected in a direction such that it is focused in the optical axis direction.

[0081] 4 is formed by processing the surface of the solid-state laser medium 3 into a convex shape by dry etching or the like, and then arranging the concave mirror 10 made of a multilayer film 42 on the formed convex surface by vapor deposition, sputtering, or the like. The concave mirror 10 is a third reflective layer R3 that reflects the incident light of the first wavelength λ1 in a direction that focuses the light in the optical axis direction of the first resonator 11. The concave mirror 10 also transmits light of the second wavelength λ2.

[0082] If the end face of the solid-state laser medium 3 is processed into a convex shape, it is not possible to bring the saturable absorber 4 into surface contact with it. Therefore, a transparent material layer 43 is formed on the concave mirror 10 disposed on the end face of the solid-state laser medium 3, the surface of the transparent material layer 43 is flattened, and the saturable absorber 4 is bonded to this transparent material layer 43.

[0083] The transparent material layer 43 may be made of any material as long as it transmits light of the second wavelength λ2. The transparent material layer 43 is formed by vapor deposition, sputtering, or the like to a thickness greater than the height of the concave mirror 10, and is polished and flattened by CMP (Chemical Mechanical Polishing) to a roughness (e.g., Ra of about 1 nm) that allows the saturable absorber 4 to be bonded. This allows stable surface contact between the transparent material layer 43 and the saturable absorber 4.

[0084] An anti-reflective coating layer 44 may be disposed between the transparent material layer 43 and the saturable absorber 4. By disposing the anti-reflective coating layer 44, there is no risk that the light of the second wavelength λ2 will be reflected at the interface between the transparent material layer 43 and the saturable absorber 4.

[0085] (Fourth Example of Laser Element 1) FIG. 5 is a cross-sectional view of a laser device 1 according to a fourth example. The laser device 1 of FIG. 5 includes an optical element 9 bonded to an end face of the solid-state laser medium 3. The optical element 9 is a member provided separately from the solid-state laser medium 3 and is a first transparent material layer. In FIG. 1, a third reflective layer R3 is disposed on the end face of the solid-state laser medium 3 facing the saturable absorber 4. However, in FIG. 5, the end face of the optical element 9 is machined into a convex shape, and a concave mirror 10 made of a multilayer film 42 is disposed on this convex surface, and this concave mirror 10 functions as the third reflective layer R3. In this way, the first transparent material layer, which is the base material of the optical element 9, has a flat surface for surface contact with the solid-state laser medium 3 and a convex end face.

[0086] The first transparent material layer, which is the base material of the optical element 9 in FIG. 5, may be made of any transparent material that transmits light of the first wavelength λ1 and the second wavelength λ2. The surface of the optical element 9 is processed into a convex shape by dry etching or the like. A concave mirror 10 made of a multilayer film 42 disposed on the convex surface reflects light of the first wavelength λ1 and transmits light of the second wavelength λ2. As in FIG. 4, a transparent material layer (also referred to as a second transparent material layer) 43 that transmits light of the second wavelength λ2 is formed on the surface of the concave mirror 10 and flattened. Therefore, the saturable absorber 4 is in stable surface contact with the transparent material layer 43. An anti-reflective coating layer 44 may be disposed at the interface between the transparent material layer 43 and the saturable absorber 4.

[0087] (Fifth Example of Laser Element 1) Fig. 6 is a cross-sectional view of a laser device 1 according to a fifth example. Laser device 1 in Fig. 6 includes an optical element 9 having a concave mirror 10a corresponding to concave mirror 10 in Fig. 2 and a concave mirror 10b corresponding to concave mirror 10 in Fig. 4. Concave mirror 10a has a multilayer film 42a arranged along its concave surface, and concave mirror 10b has a multilayer film 42b arranged along its concave surface.

[0088] 2 and 4 both reflect light of the first wavelength λ1 in a direction that focuses the incident light in the optical axis direction of the first resonator 11. Therefore, by providing both the concave mirror 10 of Fig. 2 and the concave mirror 10 of Fig. 4, diffraction loss can be further suppressed, and the light intensity of the laser output can be further improved.

[0089] (Sixth Example of Laser Element 1) The laser devices 1 according to the first to fifth specific examples described above aim to suppress diffraction loss by reflecting the light of the first wavelength λ1 in a direction in which the light is focused in the optical axis direction by using a concave mirror 10 as at least one of the first reflective layer R1 and the third reflective layer R3 of the first resonator 11. In contrast, the laser devices 1 according to the seventh to ninth specific examples described below have an optical element 9 having a light refracting member inside the pumping light source 2 to refract the light of the first wavelength λ1 in a direction in which the light is focused.

[0090] Fig. 7 is a cross-sectional view of a laser device 1 according to a sixth example. The laser device 1 of Fig. 7 includes an optical element 9 having a light refraction member 46 inside the excitation light source 2. The light refraction member 46 of Fig. 7 is formed by processing the surface of a substrate inside the excitation light source 2 into a convex shape by dry etching or the like. The light refraction member 46 functions as a convex lens, and refracts light of the first wavelength λ1 incident from the first reflecting surface side in a direction to collimate the light and emits the light, and refracts light of the first wavelength λ1 incident from the third reflecting surface side in a direction to focus the light in the optical axis direction and emits the light.

[0091] If the end face of the excitation light source 2 on the side of the solid-state laser medium 3 is convex, it cannot come into surface contact with the solid-state laser medium 3, so a transparent material layer 47 with a smaller refractive index than the substrate in the excitation light source 2 is formed on the convex surface, flattened by CMP or the like, and then bonded to the solid-state laser medium 3. The transparent material layer 47 is made of a material with a smaller refractive index than the material of the substrate of the excitation light source 2, and needs to be formed thick enough to flatten the convex surface.

[0092] 7 shows a bottom-emission type laser device 1, but in the case of a top-emission type, the DBR, which is the material of the first reflective layer R1 in Fig. 7, will be placed near the second reflective layer R2. Since the DBR cannot be processed into a convex shape, the substrate 5 bonded to the DBR is processed into a convex shape to form the light refracting member 46.

[0093] (Seventh Example of Laser Element 1) Fig. 8 is a cross-sectional view of a laser device 1 according to a seventh specific example. In the laser device 1 of Fig. 8, an optical element 9 made of a light refracting member 46 is disposed between the excitation light source 2 and the solid-state laser medium 3. This light refracting member 46 functions as a convex lens. In Fig. 7, the convex light refracting member 46 is formed by processing the substrate of the excitation light source 2, whereas in Fig. 8, the convex light refracting member 46 is disposed separately from the excitation light source 2.

[0094] The light refraction member 46 in Fig. 8 is formed by depositing a first transparent material layer 47 on the end face of the excitation light source 2 to a thickness that allows a convex surface to be formed, and then processing the first transparent material layer 47 into a convex shape by dry etching or the like. As in Fig. 8, the solid-state laser medium 3 cannot be brought into surface contact with the convex surface as it is, so a second transparent material layer 47 having a refractive index smaller than that of the first transparent material layer 47 is deposited on the convex surface by vapor deposition, sputtering, or the like, and is flattened by CMP before the solid-state laser medium 3 is bonded. Note that an anti-reflection coating layer 44 may be disposed between the light refraction member 46 and the substrate 5 of the excitation light source 2.

[0095] (Eighth Example of Laser Element 1) FIG. 9 is a cross-sectional view of a laser device 1 according to an eighth example. In the laser device 1 of FIG. 9, the end face of the solid-state laser medium 3 facing the pumping light source 2 is processed into a convex shape by dry etching or the like, and a multilayer film 42 is formed on the convex surface to form a light refraction member 46. The multilayer film 42 of this light refraction member 46 functions as a second reflective layer R2 that transmits light of the first wavelength λ1 and reflects light of the second wavelength λ2. This allows the light refraction member 46 to function as a convex lens for light of the first wavelength λ1. Because the multilayer film 42 of the light refraction member 46 has a convex shape, a transparent material layer 47 that transmits light of the first wavelength λ1 is formed on the multilayer film 42 and then planarized by CMP or the like. This allows the transparent material layer 47 and the pumping light source 2 to be firmly bonded together.

[0096] In the sixth to eighth specific examples described above, examples have been shown in which the optical element 9 is the light refracting member 46, but the light of the first wavelength λ1 can also be focused in the optical axis direction by an optical element 9 having a fine periodic structure. Examples of fine periodic structures include a Fresnel lens, a metalens, and a photonic crystal lens. Furthermore, the light of the first wavelength λ1 can also be focused in the optical axis direction by an optical element 9 having a structure with a refractive index distribution in a plane intersecting the optical axis. Examples of structures with a refractive index distribution include a GRIN lens and a substrate such as glass modified by irradiating it with laser light.

[0097] (Ninth Example of Laser Element 1) As described above, the excitation light source 2 is a form of VCSEL, and therefore it is also possible to arrange laser light sources in an array in one or two dimensions.

[0098] FIG. 10 is a cross-sectional view of a laser device 1 according to a ninth example. In the pumping light source 2 of FIG. 10, a portion of the semiconductor layer including the active layer 7 is divided into a plurality of divided regions, each of which has a first resonator 11 and a second resonator 12. This forms a laser array. In FIG. 10, the above-described optical element 9 is provided in each divided region, thereby enabling the light of the first wavelength λ1 in the first resonator 11 to be focused in the optical axis direction in each divided region. Therefore, diffraction loss can be suppressed in each divided region. Similarly to FIG. 2, the laser device 1 of FIG. 10 illustrates an example in which the first reflecting surface R1 in each divided region is a concave mirror 10. The optical element 9 is not limited to that of the first example, and may be the same as any of the second to eighth examples described above.

[0099] (Other Modifications of Laser Element 1) In the laser device 1 according to the present disclosure, the pumping light source 2 and the solid-state laser medium 3 are joined together, and therefore thermal interference may occur between the pumping light source 2 and the solid-state laser medium 3. When thermal interference occurs, the conversion efficiency from the first wavelength λ1 to the second wavelength λ2 in the solid-state laser medium 3 decreases. Also, the temperature inside the pumping light source 2 increases, and the IL characteristics (light emission efficiency) of the pumping light source 2 decrease. Furthermore, the temperature of the active layer 7 in the pumping light source 2 increases, and the long-term reliability (MTTF: Mean Time To Failure) deteriorates.

[0100] To prevent thermal interference between the pumping light source 2 and the solid-state laser medium 3, it is desirable to provide a heat exhaust member between them. The heat exhaust member is, for example, sapphire or diamond, which has a refractive index and linear expansion coefficient equivalent to those of YAG, but a higher thermal conductivity than YAG. For example, by laminating a sapphire layer between the pumping light source 2 and the solid-state laser medium 3, the above-mentioned problems can be avoided without compromising the advantages of compact integration.

[0101] Furthermore, in the laser element 1 according to the present disclosure, the cavity length of the second cavity 12 can be shortened by miniaturizing and integrating the laser element 1, thereby shortening the pulse width of the laser pulse emitted from the laser element 1. As the pulse width of the laser pulse becomes shorter, the peak power increases, making optical damage more likely to occur than in the past.

[0102] Optical damage occurs not only inside the second resonator 12 that generates the Q-switched laser pulse, but also inside the pumping light source 2 because of the return light generated on the pumping light source 2 side. In particular, the semiconductor layer 2 of the stacked structure that constitutes the pumping light source 2 is made of a material with a small band gap, so optical damage is likely to occur due to multiphoton absorption by the short-pulse laser light. For this reason, it is desirable to arrange multiple short wave pass filters (SWPFs) at multiple interfaces between the pumping light source 2 and the solid-state laser medium 3 while shortening the resonator length.

[0103] The laser element 1 and laser device according to the present disclosure employ a layered structure in which the optical axis of the excitation light and the optical axis of the laser light are coaxial. The laser element 1 and laser device according to the present disclosure do not require complex positional and angular alignment, simplifying the structure. This makes it easy to miniaturize the laser element 1 and laser device. Furthermore, by stacking or bonding multiple materials on the same semiconductor substrate, multiple laser elements 1 according to the present disclosure can be simultaneously formed. Since each laser element 1 can be separated by dicing in a subsequent process, high-performance laser elements 1 can be mass-produced at low cost.

[0104] (Method for manufacturing laser device 1 of the present disclosure) Fig. 11 is a diagram schematically showing the manufacturing process of the laser device 1 of the present disclosure. Fig. 11 shows the manufacturing process for forming the laser device 1 having the structure of Fig. 5. First, as shown in step S1 of Fig. 11, a resist film 21 is applied to a substrate 13 for the optical element 9 to be bonded to the end face of the solid-state laser medium on the side of the saturable absorber 4, and a photomask 22 is placed on the resist film 21, followed by UV exposure.

[0105] 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 convex portions 23 on the third surface of the saturable absorber 4. Next, as shown in step S3, a multilayer film 24 is formed on the plurality of convex portions 23 by vapor deposition, sputtering or the like to form a concave mirror 10 on the surface of the optical element 9.

[0106] Next, as shown in step S4, the semiconductor layer 2 for the excitation light source 2, the solid-state laser medium 3, the optical element 9 processed in step S2, and the saturable absorber 4 are vertically arranged and aligned. At this time, alignment marks 25 provided at specific locations on the semiconductor layer 2, the solid-state laser medium 3, the optical element 9, and the saturable absorber 4 are photographed with a camera 26, and the semiconductor layer 2, the solid-state laser medium 3, the optical element 9, 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 laser elements 1 are singulated by dicing.

[0107] (Effects of laser device 1 of the present disclosure) As described above, in the laser device 1 according to the present disclosure, the optical element 9 that focuses the light of the first wavelength λ1 in the optical axis direction is provided inside the first resonator 11, so that the proportion of the light of the first wavelength λ1 that leaks out from the first resonator 11 can be reduced, thereby suppressing diffraction loss. By suppressing diffraction loss, the light intensity of the laser light emitted from the laser device 1 can be increased.

[0108] 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, the above-mentioned optical element 9 is provided inside the first resonator 11. The optical element 9 is formed, for example, by processing the end face of the pumping light source 2 or the solid-state laser medium 3 into a convex shape, and can be formed without adding any new members. The laser device 1 according to the present disclosure 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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 concave mirror 10 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 can suppress short-term and long-term fluctuations in the laser output, facilitates optical adjustment to obtain oscillation light from the excitation light source 2, and realizes a light source with improved mass productivity.

[0114] 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.

[0115] 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 18 in which a plurality of laser elements 1 are two-dimensionally arranged on a single substrate.

[0116] 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.

[0117] 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.

[0118] The laser element 1 in FIG. 1 shows an example in which the excitation light source 2, the solid-state laser medium 3, and the saturable absorber 4 are integrally bonded together, but as shown in FIG. 12, a first transparent medium 27 that transmits light of a first wavelength λ1 may be disposed between the excitation light source 2 and the solid-state laser medium 3.

[0119] 12, 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.

[0120] 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.

[0121] (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 diffraction loss may also occur in a laser element 1 that does not have a saturable absorber 4 and emits CW laser light.

[0122] FIG. 13 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. 13 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 excitation 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 of the solid-state laser medium 3 or on the rear side of the second surface along the optical axis.

[0123] Fig. 13 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. 13, the third reflective layer R3 needs to have the property of transmitting light of the second wavelength λ2.

[0124] 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 λ1 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.

[0125] The third reflective layer R3 and the fourth reflective layer R4 may be integrated into a single reflective layer. In this case, the integrated reflective layer reflects light of the first wavelength λ1 and light of the second wavelength λ2. By providing the laser device 1 of FIG. 13 with an optical element 9 shown in any one of FIGS. 2 to 9, diffraction loss can be suppressed.

[0126] In this way, even if the laser element 1 does not have a saturable absorber 4, by providing the optical element 9, the light of the first wavelength λ1 in the first resonator 11 can be focused in the optical axis direction, thereby suppressing diffraction loss.

[0127] <<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.

[0128] [Endoscope system] An example of an endoscopic system will be described with reference to FIGS. 14 and 15. FIG. 14 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. 15 is a diagram illustrating an example of the configuration of an endoscope 5001 and a CCU (Camera Control Unit) 5039. FIG. 14 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. 14, 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.

[0129] 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.

[0130] 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.

[0131] [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. 15 , 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.

[0132] [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. 15 . 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.

[0133] 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).

[0134] [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.

[0135] [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.

[0136] [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.

[0137] [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.

[0138] [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.

[0139] 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.

[0140] [Microscope system] 16 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.

[0141] 16 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.

[0142] 16, during surgery, a microsurgical system 5300 is used, and an image of the surgical site captured by a microscope device 5301 is enlarged and displayed 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.

[0143] 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.

[0144] 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 surrounding area of the affected area.

[0145] 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, the first resonator has an optical element that focuses the light of the first wavelength in an optical axis direction; A laser element, wherein the optical axis of the laminated semiconductor layer, the optical axis of the laser medium, and the optical axis of the optical element are arranged on a single axis. (2) The laser element according to (1), wherein the optical element has a concave mirror. (3) The laser element according to (2), wherein the concave mirror has a multilayer structure in which at least one of a semiconductor material, a metal material, and a dielectric material is laminated. (4) The laser element according to (2) or (3), wherein at least one of the first reflective layer and the third reflective layer has the concave mirror. (5) The laminated semiconductor layer includes a first semiconductor layer having a concave end face on the first reflecting layer side, The laser element according to any one of (2) to (4), wherein the concave mirror is stacked on the first semiconductor layer. (6) The laser medium has a concave end face on the third reflecting layer side, The laser element according to any one of (2) to (4), wherein the concave mirror is laminated on the end surface of the laser medium. (7) The laser element according to any one of (2) to (4), wherein the optical element is bonded to an end face of the laser medium opposite to the side facing the laminated semiconductor layer. (8) The optical element has a first transparent material layer that transmits light of the second wavelength, a first end surface of the first transparent material layer bonded to the laser medium is a flat surface, and a second end surface opposite to the first end surface is a concave surface; The laser element according to (7), wherein the concave mirror is disposed along the second end face. (9) A second transparent material layer is bonded to the second end surface of the first transparent material layer and transmits light of the second wavelength, The laser element according to (8), wherein an end face of the second transparent material layer opposite to the bonding surface with the first transparent material layer is a flat surface. (10) The laser element according to (1), wherein the optical element has a light refracting member that refracts incident light in the direction of the optical axis. (11) The laminated semiconductor layer includes a fifth reflective layer that is disposed closer to the laser medium than the active layer and transmits a part of the light of the first wavelength, The laser element according to (10), wherein the light refracting member is disposed between the fifth reflective layer and the second reflective layer. (12) The laser element according to (11), wherein the light refracting member has a convex end face on the side of the laminated semiconductor layer facing the laser medium. (13) The optical element is bonded to an end face of the laminated semiconductor layer facing the laser medium, The laser element according to (11), wherein the light refracting member has one end face of a convex shape on a side of the optical element facing the laser medium. (14) The optical element has a transparent material layer bonded to the light refracting member and transmitting light of the first wavelength, the transparent material layer has a refractive index smaller than that of the light refracting member, The laser element according to (13), wherein the bonding surface of the transparent material layer with the light refracting member is concave, the end surface opposite to the bonding surface is flat, and the end surface of the laser medium is bonded to the flat surface. (15) The laser element according to (10), wherein the light refracting member has a convex end face on the side of the laser medium facing the laminated semiconductor layer. (16) The laser element according to (15), wherein the second reflective layer is disposed along the end face of the convex shape. (17) The optical element has a transparent material layer bonded to the light refracting member and transmitting light of the first wavelength, The laser element according to (15) or (16), wherein a bonding surface of the transparent material layer with the light refracting member is concave, an end surface opposite to the bonding surface is flat, and an end surface of the laminated semiconductor layer is bonded to the flat surface. (18) A part of the semiconductor layer including the active layer in the laminated semiconductor layer is divided into a plurality of divided regions by an insulator, The laser element according to any one of (1) to (17), wherein each of the plurality of divided regions has the first resonator and the second resonator. (19) 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, an optical axis of the saturable absorber, and an optical axis of the optical element are arranged on a single axis; The laser element according to any one of (1) to (18), wherein the laminated semiconductor layer, the laser medium, and the saturable absorber are integrally bonded together. (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, the first resonator has an optical element that focuses the light of the first wavelength in an optical axis direction; an optical axis of the laminated semiconductor layer, an optical axis of the laser medium, and an optical axis of the optical element are arranged on a single axis.

[0146] 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]

[0147] 1 laser element, 2 laminated semiconductor layer, 2 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, 10 concave mirror, 10a concave mirror, 10b concave mirror, 11 first resonator, 12 second resonator, 13 substrate, 18 laser array, 21 resist film, 22 photomask, 23 convex portion, 24 multilayer film, 25 alignment mark, 26 camera, 27 first transparent medium, 28 second transparent medium, 31 contact layer, 32 oxide layer (e.g., Al2O3 layer), 33 contact layer, 34 insulating film, 41 concave mirror forming layer, 42 multilayer film, 42a multilayer film, 42b multilayer film, 43 transparent material layer, 44 anti-reflection coating layer, 46 photorefractive member, 47 transparent material layer

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 semiconductor layer and a light source disposed behind the semiconductor layer and on the optical axis of the semiconductor layer; a laser medium having a second reflective layer for a second wavelength on an opposing first surface 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, the first resonator has an optical element that focuses the light of the first wavelength in an optical axis direction; an optical axis of the laminated semiconductor layer, an optical axis of the laser medium, and an optical axis of the optical element are arranged on a single axis; the optical element includes a concave mirror; the laser medium has a concave end face on the third reflective layer side, the concave mirror is laminated on the end surface of the laser medium; Laser element.

2. 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 semiconductor layer and a light source disposed behind the semiconductor layer and on the optical axis of the semiconductor layer; a laser medium having a second reflective layer for a second wavelength on an opposing first surface 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, the first resonator has an optical element that focuses the light of the first wavelength in an optical axis direction; an optical axis of the laminated semiconductor layer, an optical axis of the laser medium, and an optical axis of the optical element are arranged on a single axis; the optical element has a concave mirror and is bonded to an end face of the laser medium opposite to the side facing the laminated semiconductor layer; Laser element.

3. the optical element has a first transparent material layer that transmits light of the second wavelength; a first end surface of the first transparent material layer that is bonded to the laser medium is a flat surface, and a second end surface opposite to the first end surface is a concave surface; the concave mirror is disposed along the second end surface; The laser device according to claim 2 .

4. a second transparent material layer bonded to the second end surface of the first transparent material layer and transmitting light of the second wavelength; an end surface of the second transparent material layer opposite to a bonding surface with the first transparent material layer is a flat surface; The laser device according to claim 3 .

5. the concave mirror has a multilayer structure in which at least one of a semiconductor material, a metal material, and a dielectric material is laminated; The laser device according to claim 1 .

6. At least one of the first reflective layer and the third reflective layer has the concave mirror. The laser device according to claim 1 .

7. 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 semiconductor layer and a light source disposed behind the semiconductor layer and on the optical axis of the semiconductor layer; a laser medium having a second reflective layer for a second wavelength on an opposing first surface 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, the first resonator has an optical element that focuses the light of the first wavelength in an optical axis direction; an optical axis of the laminated semiconductor layer, an optical axis of the laser medium, and an optical axis of the optical element are arranged on a single axis; the optical element includes a light refracting member that refracts incident light in an optical axis direction, and a transparent material layer that is bonded to the light refracting member and transmits light of the first wavelength, and is bonded to an end face of the laminated semiconductor layer that faces the laser medium; the laminated semiconductor layer has a fifth reflective layer that is disposed closer to the laser medium than the active layer and transmits a part of the light of the first wavelength; the light refracting member has one end surface of a convex shape on a side of the optical element facing the laser medium, and is disposed between the fifth reflective layer and the second reflective layer, the transparent material layer has a refractive index smaller than that of the light refracting member, a bonding surface of the transparent material layer with the light refracting member having a concave shape, an end surface opposite to the bonding surface being a flat surface, and an end surface of the laser medium being bonded to the flat surface; Laser element.

8. 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 semiconductor layer and a light source disposed behind the semiconductor layer and on the optical axis of the semiconductor layer; a laser medium having a second reflective layer for a second wavelength on an opposing first surface 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, the first resonator has an optical element that focuses the light of the first wavelength in an optical axis direction; an optical axis of the laminated semiconductor layer, an optical axis of the laser medium, and an optical axis of the optical element are arranged on a single axis; the optical element has a light refracting member that refracts incident light in the optical axis direction, the light refracting member has a convex end face on a side of the laser medium facing the laminated semiconductor layer, Laser element.

9. the second reflective layer is disposed along the end surface of the convex shape. The laser device according to claim 8 .

10. the optical element has a transparent material layer bonded to the light refractive member and transmitting light of the first wavelength; a bonding surface of the transparent material layer with the light refracting member having a concave shape, an end surface opposite to the bonding surface being a flat surface, and an end surface of the laminated semiconductor layer being bonded to the flat surface; 10. The laser device according to claim 8 or 9.

11. a part of the semiconductor layer including the active layer in the laminated semiconductor layer is divided into a plurality of divided regions by an insulator, Each of the plurality of divided regions includes the first resonator and the second resonator.

11. The laser device according to claim 1.

12. 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, an optical axis of the saturable absorber, and an optical axis of the optical element are arranged on a single axis; the laminated semiconductor layer, the laser medium, and the saturable absorber are integrally bonded together; 12. A laser device according to any one of claims 1 to 11.

13. A laser element according to any one of claims 1 to 12, A control unit that controls the emission of light from the laser element. electronic equipment.

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