Laser elements and electronic devices

Abstract

[Problem] To provide a laser element wherein a plurality of optical elements are integrated to enable suppression of a standing wave of excitation light or oscillation light. [Solution] This laser element comprises: a laminated semiconductor layer having a first reflection layer and an active layer that performs surface light emission of a first wavelength; a laser medium having a second reflection layer on a first surface thereof and a third reflection layer on a second surface thereof; a fourth reflection layer located behind the second surface along an optical axis; a first resonator for resonating a first wavelength light between the first and third reflection layers; a second resonator for resonating a second wavelength light between the second reflection layer and the fourth reflection layer; a first polarization converting element located between the first reflection layer and the laser medium; a second polarization converting element located between the second reflection layer and the laser medium; and at least one of a first or second polarization control element located between the first reflection layer and the fourth reflection layer. The optical axis of the laminated semiconductor layer, the optical axis of the laser medium, and the optical axes of the first and second polarization converting elements and the first or second polarization control element are located on a single 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 the pulse energy divided by the pulse width, and a shorter pulse width is important to obtain a higher peak power. Q-switched solid-state lasers that output laser pulses have the characteristic that the pulse width obtained is proportional to the length of their resonator, and the minimum resonator length is affected by the length of the solid-state laser medium used. On the other hand, 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. Therefore, simply shortening the length of the solid-state laser medium results in insufficient absorption of the pump light, resulting in 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 viewpoint of manufacturing and light source output stability, conventional Q-switched solid-state lasers require highly accurate positioning of multiple optical elements and assembly adjustment, which makes them unsuitable for mass production, makes it difficult to reduce costs, and also poses issues with the stability of light source output due to misalignment of each optical element.

[0005] In integrating optical elements, a configuration in which a solid-state laser medium is shared by a resonator for pumping light and a resonator for oscillating light can be considered. However, in this case, the pumping light or oscillating light that excites the solid-state laser medium may resonate in the respective resonators, resulting in standing waves in the solid-state laser medium. This can cause a decrease in the pumping efficiency and stability of the solid-state laser medium. [Prior art documents] [Patent documents]

[0006] [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 [Patent Document 4] International Publication No. WO2019 / 049694 Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, the present disclosure provides a laser element that can suppress standing waves in excitation light or oscillation light while integrating multiple optical elements. [Means for solving the problem]

[0008] A laser element according to one aspect of the present disclosure includes a laminated semiconductor layer having a first reflective layer for a first wavelength and an active layer that performs surface emission of light of the first wavelength; a laser medium that is disposed on the rear side of the optical axis of the laminated semiconductor layer and has 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 that is disposed on the second surface or disposed rearward of the second surface along the optical axis; a first resonator that resonates light of the first wavelength between the first reflective layer and the third reflective layer; a second resonator that resonates light of the second wavelength between the second reflective layer and the fourth reflective layer; a first polarization conversion element provided between the second reflective layer and the laser medium, which changes the phase of light having a first or second wavelength in a vibration direction perpendicular to each other; a second polarization conversion element provided between the second reflective layer and the laser medium, which changes the phase of light having a first or second wavelength in a vibration direction perpendicular to each other; and at least one of a first or second polarization control element provided between the first reflective layer and the fourth reflective layer, which controls polarization of light having the first or second wavelength; and the optical axes of the laminated semiconductor layer, the optical axis of the laser medium, the first and second polarization conversion elements, and the first or second polarization control element are arranged on a single axis.

[0009] The first and second polarization conversion elements are made of an anisotropic material, a metasurface structure, or a photonic crystal structure.

[0010] The first and second polarization conversion elements respectively impart a phase difference of approximately a quarter wavelength to light of the first and second wavelengths vibrating in directions orthogonal to each other.

[0011] The laser device further includes a fifth reflective layer provided on the laser medium side of the laminated semiconductor layers.

[0012] The first polarization control element is provided between the first reflective layer and the first polarization conversion element, and controls the polarization of light of the first wavelength.

[0013] The second polarization control element is provided between the fourth reflective layer and the second polarization conversion element, and controls the polarization of light of the second wavelength.

[0014] The first polarization control element has a fine structure on its surface so as to have different transmittances for mutually orthogonal polarized light beams of the first wavelength.

[0015] The second polarization control element has a fine structure on its surface so as to have different transmittances for mutually orthogonal polarized light of the second wavelength.

[0016] The optical fiber further includes a saturable absorber disposed between the third and fourth reflective layers.

[0017] The first polarization conversion element is disposed between the first polarization control element and the second reflective layer, and the second polarization conversion element is disposed between the laser medium and the third reflective layer.

[0018] the first polarization conversion element is disposed between the second reflective layer and the laser medium; The second polarization conversion element is disposed between the third reflective layer and the second polarization control element.

[0019] The first polarization conversion element is disposed between the second reflective layer and the laser medium, and the second polarization conversion element is disposed between the laser medium and the third reflective layer.

[0020] The fourth reflective layer has a microstructure on its surface so as to have different transmittances for the orthogonally polarized light of the second wavelength.

[0021] The saturable absorber has a microstructure on its surface that has different transmittances for the orthogonal polarized light of the second wavelength.

[0022] The fourth reflective layer causes a phase difference between the light of the second wavelength and the light of the vibration directions that are orthogonal to each other.

[0023] The first polarization control element is disposed between the second reflective layer and the first polarization conversion element, and has a microstructure on its surface so as to have different transmittances for mutually orthogonal polarized light of the first wavelength, and different transmittances for mutually orthogonal polarized light of the second wavelength.

[0024] The second polarization control element is disposed between the third reflective layer and the second polarization conversion element, and has a microstructure on its surface so as to have different transmittances for mutually orthogonal polarized light of the first wavelength, and different transmittances for mutually orthogonal polarized light of the second wavelength.

[0025] The first polarization conversion element has a fine structure on its surface so as to have different transmittances for mutually orthogonal polarized light of the first wavelength.

[0026] The second polarization conversion element has a microstructure on its surface so as to have different transmittances for mutually orthogonal polarized light of the second wavelength.

[0027] The laminated semiconductor layer, the laser medium, the fourth reflecting layer, the first resonator, the second resonator, the first polarization conversion element, the second polarization conversion element, and the first or second polarization control element are integrally bonded together.

[0028] The optical element further includes a transparent member provided somewhere between the first reflective layer and the fourth reflective layer.

[0029] An electronic device according to one aspect of the present disclosure is an electronic device including a laser element and a control unit that controls emission of light from the laser element, wherein the laser element includes: a laminated semiconductor layer having a first reflective layer for a first wavelength and an active layer that performs surface emission of light of the first wavelength; a laser medium that is arranged on the rear side of the optical axis of the laminated semiconductor layer and has 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 that is arranged on the second surface or arranged on the 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; and a laser medium that resonates light of the first wavelength between the second reflective layer and the fourth reflective layer. a second resonator that resonates light of the second wavelength between the first and second resonators, a first polarization conversion element that is provided between the first reflective layer and the laser medium and that changes the phase of light of the first wavelength in vibration directions that are orthogonal to each other, a second polarization conversion element that is provided between the second reflective layer and the laser medium and that changes the phase of light of the second wavelength in vibration directions that are orthogonal to each other, and at least one of a first or second polarization control element that is provided between the first reflective layer and the fourth reflective layer and that controls polarization of light of the first or second wavelength, and the optical axes of the laminated semiconductor layers, the optical axis of the laser medium, the first and second polarization conversion elements, and the first or second polarization control element are arranged on a single axis. [Brief explanation of the drawings]

[0030] [Figure 1] 1 is a diagram showing the basic configuration of a laser element according to the present disclosure. [Figure 2A] FIG. 1 is a cross-sectional view showing an example of the configuration of a laser element according to a first embodiment. [Figure 2B] FIG. 1 is a cross-sectional view showing an example of the configuration of a laser element including a transparent member. [Figure 3] FIG. 10 is a cross-sectional view showing an example of the configuration of a laser element according to a second embodiment. [Figure 4] FIG. 10 is a cross-sectional view showing an example of the configuration of a laser element according to a third embodiment. [Figure 5] FIG. 10 is a cross-sectional view showing an example of the configuration of a laser element according to a fourth embodiment. [Figure 6] FIG. 10 is a cross-sectional view showing an example of the configuration of a laser element according to a fifth embodiment. [Figure 7] FIG. 10 is a cross-sectional view showing an example of the configuration of a laser element according to a sixth embodiment. [Figure 8] FIG. 13 is a cross-sectional view showing an example of the configuration of a laser element according to a seventh embodiment. [Figure 9] FIG. 13 is a cross-sectional view showing an example of the configuration of a laser element according to an eighth embodiment. [Figure 10] FIG. 13 is a cross-sectional view showing an example of the configuration of a laser element according to a ninth embodiment. [Figure 11] FIG. 23 is a cross-sectional view showing a configuration example of a laser element according to a tenth embodiment. [Figure 12] FIG. 23 is a cross-sectional view showing an example of the configuration of a laser element according to an eleventh embodiment. [Figure 13] FIG. 23 is a cross-sectional view showing an example of the configuration of a laser element according to a twelfth embodiment. [Figure 14] FIG. 23 is a cross-sectional view showing a configuration example of a laser element according to a thirteenth embodiment. [Figure 15] FIG. 1 is a diagram showing an example of a schematic configuration of an endoscope system. [Figure 16] FIG. 16 is a block diagram showing an example of the functional configuration of the camera and the CCU shown in FIG. 15. [Figure 17] FIG. 1 is a diagram showing an example of a schematic configuration of a microsurgery system. DETAILED DESCRIPTION OF THE INVENTION

[0031] Hereinafter, specific embodiments to which the present technology is applied will be described in detail with reference to the drawings. The drawings are schematic or conceptual, and the proportions of each part are not necessarily the same as those in reality. In the specification and drawings, elements similar to those described above with reference to the previous drawings are designated by the same reference numerals, and detailed descriptions thereof will be omitted as appropriate.

[0032] (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.

[0033] The laser element according to the present disclosure has a structure in which a part of a surface-emitting laser is used as a light-emitting element, 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 without a Q-switching function, but first, a laser element with a Q-switching function will be described.

[0034] 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).

[0035] 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.

[0036] 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.

[0037] Here, the light-emitting element 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 light-emitting element. 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.

[0038] As mentioned above, by integrating multiple optical elements within a laser device, the laser device can generate laser pulses with short pulse widths by Q-switching. Here, when integrating optical elements, a configuration in which a solid-state laser medium is shared by a pump light resonator and an oscillation light resonator is considered. However, in this case, the pump light or oscillation light that excites the solid-state laser medium resonates in its respective resonator, forming a standing wave in the solid-state laser medium. The standing wave of the pump light does not excite the solid-state laser medium at its nodes, reducing the excitation efficiency. Furthermore, the standing wave of the pump light causes re-absorption of the oscillation light in the solid-state laser medium. The standing wave of the oscillation light causes the so-called spatial hole burning phenomenon.

[0039] Therefore, in the laser device according to the present disclosure, polarization conversion elements are provided on both sides of the solid-state laser medium to cause a phase difference between the excitation light or oscillation light having mutually orthogonal vibration directions, and a polarization control element is provided to cause laser oscillation of only polarized light in one direction, thereby making it possible to suppress the generation of standing waves in the excitation light or oscillation light without compromising the advantage of a compact, integrated structure.

[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 light-emitting element and a solid-state laser medium. The second resonator includes a solid-state laser medium and a saturable absorber, and Q-switched laser oscillation is performed by the excitation light from the first resonator.

[0041] (2) A polarization conversion element that changes the phase of the pumping light and / or oscillation light in mutually orthogonal vibration directions is provided on each side of the solid-state laser medium. Furthermore, at least one polarization control element for controlling polarization in one direction is provided in the resonator between the polarization conversion element and the reflective layer on the opposite side of the solid-state laser medium. These polarization conversion elements and polarization control elements suppress standing waves of the pumping light and / or oscillation light in the solid-state laser medium.

[0042] (3) The light emitting element, 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 the light-emitting element is absorbed by the solid-state laser medium in the first resonator. The solid-state laser medium, together with a saturable absorber installed in 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 a light-emitting element 2, a solid-state laser medium 3, and a saturable absorber 4 are integrally bonded together.

[0044] The light-emitting element 2 has semiconductor layers with a laminated structure (laminated semiconductor layers). The light-emitting element 2 in Fig. 1 has a structure in which a substrate 5, a fifth reflective layer R5, a cladding layer 6, an active layer 7, a cladding layer 8, and a first reflective layer R1 are laminated in this order. Note that although the laser element 1 in Fig. 1 shows a bottom emission type configuration in which continuous wave (CW) excitation light is emitted from the substrate 5, it may also have a top emission type configuration in which CW excitation 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 light of the first wavelength λ1, which is the excitation wavelength of the light-emitting element 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. The cladding layers 6 and 8 are, for example, AlGaAs cladding layers. The first reflective layer R1 reflects light of the first wavelength λ1. The fifth reflective layer R5 has a certain transmittance for light of the first wavelength λ1. The first reflective layer R1 and the fifth reflective layer R5 are, for example, electrically conductive semiconductor distributed Bragg reflectors (DBRs). Current is injected from the outside through the first reflective layer R1 and the fifth reflective layer R5, causing recombination and light emission in the quantum wells in the active layer 7, resulting in laser oscillation of the first wavelength λ1. A portion of the surface layer (for example, an AlAs layer) 31A on the cladding layer side of the first reflective layer R1 is oxidized to form an oxide layer (for example, an Al2O3 layer) 32.

[0047] The fifth reflective layer R5 is provided on the solid-state laser medium 3 side of the light-emitting element 2, and is provided between the semiconductor layer of the light-emitting element 2 and the solid-state laser medium 3. The fifth reflective layer R5 is disposed on, for example, an n-GaAs substrate 5. For example, the fifth reflective layer R5 is made of Al doped with an n-type dopant (for example, silicon). z1 Ga 1-z1 As / Al z2 Ga 1-z2 The fifth reflective layer R5 has a multilayer reflective film made of As (0≦z1≦z2≦1). The fifth reflective layer R5 is also called an n-DBR. More specifically, an n-contact layer 33 is disposed between the fifth reflective layer R5 and the n-GaAs substrate 5.

[0048] The active layer 7 is made of, for example, Al x1 In y1 Ga 1-x1-y1 As layer and Al x3 In y3 Ga 1-x3-y3 It has a multi-quantum well layer with an As layer stacked thereon.

[0049] The first reflective layer R1 is, for example, Al doped with a p-type dopant (for example, carbon). z3 Ga 1-z3 As / Al Z4 Ga 1-z4 The first reflective layer R1 has a multi-reflection film made of As (0≦z3≦z4≦1). The first reflective layer R1 is also called a p-DBR.

[0050] The semiconductor layers R5, 6, 7, 8, and R1 in the light-emitting element 2 can be formed using a crystal growth method such as MOCVD (metal organic chemical vapor deposition) or MBE (molecular beam epitaxy). After the crystal growth, processes such as mesa etching for element isolation, formation of an insulating film, and deposition of an electrode film are performed, enabling the element to be driven by current injection.

[0051] The solid-state laser medium 3 is bonded to the end face of the n-GaAs substrate 5 of the light-emitting element 2 opposite to the fifth reflection layer R5. Hereinafter, the end face of the solid-state laser medium 3 facing the light-emitting element 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 emission face of the saturable absorber 4 will be referred to as the third face F3, and the end face of the light-emitting element 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 light-emitting element 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] 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 light-emitting element 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.

[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 light-emitting element 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 element 1 of FIG. 1, the third reflective layer R3 is used to confine the power of the excitation 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 made up of the light-emitting element 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 excitation wavelength (first wavelength λ1) differs depending on the crystal, it is necessary to select the semiconductor material of the active layer 7 in the light-emitting element 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 light emitting element 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 stably bond the solid-state laser medium 3 to the light-emitting element 2, the surface of the n-GaAs substrate 5 within the light-emitting element 2 must be flat. Therefore, as described above, it is desirable to arrange the electrodes E1 and E2, which are used to inject current into the first reflective layer R1 and the fifth reflective layer R5, so that they are not exposed on the surface of the n-GaAs substrate 5. In the example shown in FIG. 1 , the electrodes E1 and E2 are arranged on the end face of the light-emitting element 2 facing the first reflective layer R1. The electrode E1 is a p-electrode and is electrically connected to the first reflective layer R1. The electrode E2 is an n-electrode formed by filling the inner wall of a trench extending from the first reflective layer R1 to the n-contact layer 33 with a conductive material 35 via an insulating film 34. By arranging the electrodes E1 and E2 on the same end face of the light-emitting element 2 as shown in FIG. 1 , this end face can be solder-mounted to a support substrate (not shown). Even when multiple laser elements are arranged in an array, arranging the electrodes E1 and E2 on the same end face allows this end face to be mounted on a support substrate. The shapes and locations of the electrodes E1 and E2 shown in FIG. 1 are merely examples.

[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 disposed between each layer and bonded via the dielectric multilayer film. For example, the refractive index n of the GaAs substrate 5, which serves as the base substrate of the light-emitting element 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 light-emitting element 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 light-emitting element 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 arrange different types of dielectric multilayer films as needed. The dielectric multilayer film can be formed by physical vapor deposition (PVD), specifically, vacuum deposition, ion-assisted deposition, sputtering, or other 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. Applying a long-wavelength transmission filter film to the third reflective layer R3 can prevent the first wavelength from penetrating the saturable absorber and thus prevent malfunction of the Q-switch. Note that short-wavelength transmission means transmitting light of the first wavelength λ1 and reflecting light of the second wavelength λ2. Moreover, long wavelength transmission means reflecting light of the first wavelength λ1 and transmitting light of the second wavelength λ2.

[0066] 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.

[0067] (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 light-emitting element 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.

[0068] 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).

[0069] 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.

[0070] Having explained the basic configuration and operating principle for obtaining Q-switched laser oscillation according to the present disclosure, an embodiment of the laser element according to the present disclosure will now be described.

[0071] (First embodiment) 2A is a cross-sectional view showing an example of the configuration of a laser device 1 according to the first embodiment. The laser device 1 further includes polarization conversion elements 21 and 22 and a polarization control element 31 in addition to the basic configuration of FIG. 1. The saturable absorber 4 is disposed between the third reflection layer R3 and the fourth reflection layer R4. In the embodiment of this specification, the optical elements constituting the laser device 1 (for example, the light-emitting element 2, the solid-state laser medium 3, the reflection layers R1 to R5, the resonators 11 and 12, the polarization conversion elements 21 and 22, and the polarization control element 31) are bonded together.

[0072] The polarization conversion element 21 as a first polarization conversion element is disposed somewhere between the first reflective layer R1 and the solid-state laser medium 3 in the excitation light resonator 11, on the optical axis of the excitation light resonator 11. More specifically, the polarization conversion element 21 is provided between the polarization control element 31 and the second reflective layer R2. The polarization conversion element 21 shifts the phase of light in the excitation light of the first wavelength that vibrates in directions orthogonal to each other.

[0073] The polarization conversion element 22, which serves as a second polarization conversion element, is disposed on the opposite side of the solid-state laser medium 3 from the polarization conversion element 21. The polarization conversion element 22 is disposed somewhere between the fourth reflection layer R4 and the solid-state laser medium 3, on the optical axis of the excitation light resonator 11. More specifically, the polarization conversion element 22 is provided between the third reflection layer R3 and the solid-state laser medium 3. The polarization conversion element 22 shifts the phase of light in the first-wavelength excitation light having vibration directions that are orthogonal to each other. In this way, the two polarization conversion elements 21 and 22 are disposed on both sides of the solid-state laser medium 3, sandwiching it therebetween.

[0074] The polarization conversion elements 21 and 22 impart different phase differences to the excitation light beams vibrating in directions perpendicular to each other. For example, the polarization conversion elements 21 and 22 impart a phase difference of approximately a quarter wavelength (i.e., π / 2) between the TM (Transverse Magnetic) wave and the TE (Transverse Electric) wave of the excitation light beam. In this case, the main axes of the polarization conversion elements 21 and 22 are perpendicular to each other and inclined at 45 degrees with respect to the polarization direction determined by the polarization control element 31. Note that the phase difference imparted to the excitation light beam by the polarization conversion elements 21 and 22 does not necessarily have to be a quarter wavelength. The polarization conversion elements 21 and 22 may be made of, for example, an anisotropic material, a metasurface structure, a photonic crystal structure, or the like.

[0075] In this way, the polarization conversion elements 21 and 22 impart different phase differences to the light in the excitation light having mutually orthogonal vibration directions, so that the excitation light does not become a standing wave within the solid-state laser medium 3 and can efficiently excite the solid-state laser medium 3. In this embodiment, the polarization conversion elements 21 and 22 act on the excitation light but do not act on the oscillation light of the second wavelength λ2. However, the polarization conversion elements 21 and 22 may act on the oscillation light as described below.

[0076] The polarization control element 31, which serves as a first polarization control element, is provided at a position between the first reflective layer R1 and the fourth reflective layer R4 or the polarization conversion element 21. More specifically, the polarization control element 31 is provided between the substrate 5 of the light-emitting element 2 and the polarization conversion element 21, and is disposed on the optical axis of the excitation light resonator 11. The polarization control element 31 controls the polarization of the excitation light of the first wavelength λ1. The polarization control element 31 is made of a material that is transparent to the excitation light, such as a dielectric (e.g., Al2O3, SiO2, Ta2O5, HfO2) or a semiconductor (e.g., GaN, InN, AlN). Although not shown, a grating structure is formed on the surface of the polarization control element 31 as a microstructure. This allows the polarization control element 31 to have different transmittances for mutually orthogonal polarized light (TM wave and TE wave) of the excitation light of the first wavelength λ1. The grating structure may be, for example, a concave-convex structure having a period equal to or less than the first wavelength λ1 of the excitation light and a depth equal to or less than one-fourth the first wavelength λ1 of the excitation light. The grating structure may be, for example, a one-dimensional surface relief grating structure that utilizes zero-order diffracted light (transmitted light). That is, the pattern of the grating structure may be a so-called line-and-space pattern. This allows the polarization control element 31 to have different transmittances for mutually orthogonal polarized light (TM wave, TE wave) of the zero-order diffracted light (transmitted light) of the excitation light. Furthermore, since the polarization control element 31 controls the polarization of the excitation light to one direction rather than random polarization, it is possible to improve the characteristics of the excitation light resonator 11, such as stabilizing the oscillation output and improving the wavelength conversion efficiency. The polarization control element 31 may have different transmittances for mutually orthogonal polarized light (TM wave, TE wave), and may have, for example, an anisotropic material, a diffraction grating structure, a metasurface structure, a photonic crystal structure, or the like.

[0077] According to this embodiment, polarized light of the excitation light having high transmittance to the polarization control element 31 is oscillated in the solid-state laser medium 3 so as not to become a standing wave by the polarization conversion elements 21 and 22. As a result, standing waves generated by the resonance of the excitation light in the first resonator in the solid-state laser medium 3 can be suppressed, and the solid-state laser medium 3 can be excited with high efficiency.

[0078] In the embodiments of the present specification, the transparent member HE may be provided at any position between the first reflective layer R1 and the fourth reflective layer R4. In this case, the transparent member HE functions as a spacer that adjusts the length of the optical resonator 11 or 12 in the optical axis direction. Furthermore, when the transparent member HE is adjacent to the solid-state laser medium 3, it functions both as a spacer and as a heat exhaust function that exhausts heat from the solid-state laser medium 3. For example, FIG. 2B is a cross-sectional view showing an example configuration of a laser device 1 including a transparent member HE. In FIG. 2B, the transparent member HE is adjacent to the solid-state laser medium 3 via the reflective layer R2. The transparent member HE functions both as a heat exhaust function and a function that adjusts the length of the optical resonator 11 in the optical axis direction.

[0079] (Second embodiment) 3 is a cross-sectional view showing an example of the configuration of a laser device 1 according to the second embodiment. According to the second embodiment, the polarization conversion element 21 is disposed between the second reflective layer R2 and the solid-state laser medium 3. The polarization conversion element 22 is disposed between the third reflective layer R3 and the polarization control element 32. The polarization control element 32 is also provided somewhere between the fourth reflective layer R4 and the polarization conversion element 22. More specifically, the polarization control element 32 is provided between the saturable absorber 4 and the polarization conversion element 22. As described above, in the second embodiment, the polarization conversion elements 21 and 22 and the polarization control element 32 are provided on the oscillation optical resonator 12 side, and standing waves of the oscillating light of the second wavelength λ2 are suppressed.

[0080] The polarization conversion elements 21 and 22 impart different phase differences to the light beams vibrating in directions perpendicular to each other in the oscillating light. For example, the polarization conversion elements 21 and 22 impart a phase difference of approximately a quarter wavelength (i.e., π / 2) between the TM wave and the TE wave of the oscillating light. In this case, the main axes of the polarization conversion elements 21 and 22 are perpendicular to each other and inclined at 45 degrees with respect to the polarization direction determined by the polarization control element 32. Note that the phase difference imparted to the oscillating light by the polarization conversion elements 21 and 22 does not necessarily have to be a quarter wavelength. The polarization conversion elements 21 and 22 may be made of, for example, an anisotropic material, a metasurface structure, a photonic crystal structure, or the like.

[0081] In this way, the polarization conversion elements 21 and 22 impart different phase differences to the light in the oscillation light having mutually orthogonal vibration directions, thereby preventing the oscillation light from becoming a standing wave and realizing efficient laser oscillation within the solid-state laser medium 3. In the second embodiment, the polarization conversion elements 21 and 22 act on the oscillation light but do not act on the pump light of the first wavelength λ1. However, as will be described later, there is no problem if the polarization conversion elements 21 and 22 act on the pump light.

[0082] The polarization control element 32 as a second polarization control element is provided between the saturable absorber 4 and the polarization conversion element 22 and is arranged on the optical axis of the oscillation optical resonator 12. The polarization control element 32 controls the polarization of the oscillation light of the second wavelength λ2. The polarization control element 32 is made of, for example, a dielectric material (e.g., Al2O3, SiO2, Ta2O5, HfO2) or a semiconductor (e.g., GaN, InN, AlN), etc., which is transparent to the oscillation light. Although not shown, a grating structure as a microstructure is formed on the surface of the polarization control element 32. This allows the polarization control element 32 to have different transmittances for the orthogonal polarized light (TM wave, TE wave) of the oscillation light of the second wavelength λ2. The grating structure may be, for example, a concave-convex structure having a period equal to or less than the second wavelength λ2 of the oscillation light and a depth equal to or less than one-fourth the second wavelength λ2 of the oscillation light. The grating structure may be, for example, a one-dimensional surface relief grating structure that utilizes zero-order diffracted light (transmitted light). That is, the pattern of the grating structure may be a so-called line-and-space pattern. As a result, the polarization control element 32 has different transmittances for mutually orthogonal polarized lights (TM wave, TE wave) of the zeroth-order diffracted light (transmitted light) of the oscillation light. Furthermore, the polarization control element 32 controls the polarization of the oscillation light to one direction rather than random polarization, thereby enabling improvements in the characteristics of the oscillation optical resonator 12, such as stabilization of the oscillation output and improvement of wavelength conversion efficiency. Note that the polarization control element 32 only needs to have different transmittances for mutually orthogonal polarized lights (TM wave, TE wave), and may have, for example, an anisotropic material, a diffraction grating structure, a metasurface structure, a photonic crystal structure, or the like.

[0083] Other configurations of the second embodiment may be similar to the corresponding configurations of the first embodiment. The saturable absorber 4 is provided between the polarization control element 32 and the fourth reflective layer R4. However, the saturable absorber 4 may be disposed at any position between the third reflective layer R3 and the fourth reflective layer R4.

[0084] According to the second embodiment, polarized light of the oscillating light having a high transmittance to the polarization control element 32 is oscillated in the solid-state laser medium 3 so as not to become a standing wave due to the polarization conversion elements 21 and 22. As a result, in the solid-state laser medium 3, standing waves generated by the oscillating light resonating in the second resonator are suppressed, and the oscillating light can be output stably and efficiently.

[0085] (Third embodiment) FIG. 4 is a cross-sectional view showing an example of the configuration of a laser device 1 according to the third embodiment. According to the third embodiment, the polarization conversion element 21 is disposed between the second reflective layer R2 and the solid-state laser medium 3. The polarization conversion element 22 is disposed between the solid-state laser medium 3 and the third reflective layer R3. In addition, in the third embodiment, both polarization control elements 31 and 32 are provided. The polarization control element 31 is disposed between the fifth reflective layer R5 and the second reflective layer R2. The polarization control element 32 is disposed between the saturable absorber 4 and the third reflective layer R3. As described above, in the third embodiment, the polarization conversion elements 21 and 22 are shared by both the pumping optical resonator 11 and the oscillation optical resonator 12. Furthermore, the polarization control element 31 is disposed on the pumping optical resonator 11 side, and the polarization control element 32 is disposed on the oscillation optical resonator 12 side. This makes it possible to suppress standing waves in both the pumping light of the first wavelength λ1 and the oscillation light of the second wavelength λ2.

[0086] The polarization conversion elements 21 and 22 may have the same configuration as those in the first and second embodiments. That is, the polarization conversion elements 21 and 22 impart different phase differences to the light beams vibrating in mutually orthogonal directions in both the pump light and the oscillation light. For example, the polarization conversion elements 21 and 22 impart a phase difference of approximately a quarter wavelength (i.e., π / 2) between the TM wave and the TE wave of the oscillation light and the oscillation light, respectively. In this case, the main axes of the polarization conversion elements 21 and 22 are perpendicular to each other and inclined at 45 degrees with respect to the polarization direction determined by the polarization control element 32. Note that the phase difference imparted by the polarization conversion elements 21 and 22 to the pump light and the oscillation light does not necessarily have to be a quarter wavelength.

[0087] In this way, the polarization conversion elements 21 and 22 give different phase differences to the excitation light and oscillation light whose vibration directions are orthogonal to each other, so that the excitation light and oscillation light do not become standing waves within the solid-state laser medium 3, enabling efficient laser oscillation.

[0088] The polarization control element 31 is provided between the light emitting element 2 and the second reflective layer R2, and is disposed on the optical axis of the excitation light resonator 11. The polarization control element 31 controls the polarization of the excitation light of the first wavelength λ1.

[0089] The polarization control element 32 is provided between the third reflective layer R3 and the saturable absorber 4, and is disposed on the optical axis of the oscillation optical resonator 12. The polarization control element 32 controls the polarization of the oscillation light of the second wavelength λ2. The configurations of the polarization control elements 31 and 32 may be similar to those of the first and second embodiments.

[0090] Other configurations of the third embodiment may be similar to the corresponding configurations of the first or second embodiment.

[0091] According to the third embodiment, polarized light of the excitation light having a high transmittance to the polarization control element 31 oscillates in the solid-state laser medium 3 so that it does not become a standing wave due to the polarization conversion elements 21 and 22. This suppresses standing waves of the excitation light in the solid-state laser medium 3, enabling highly efficient excitation of the solid-state laser medium 3. Furthermore, polarized light of the oscillation light having a high transmittance to the polarization control element 32 oscillates in the solid-state laser medium 3 so that it does not become a standing wave due to the polarization conversion elements 21 and 22. This suppresses standing waves of the oscillation light in the solid-state laser medium 3, enabling stable and highly efficient laser oscillation.

[0092] (Fourth embodiment) FIG. 5 is a cross-sectional view showing an example of the configuration of a laser device 1 according to the fourth embodiment. In the fourth embodiment, the fourth reflective layer R4 of the second embodiment also functions as the polarization control element 32. That is, the polarization control element 32 for the oscillating light and the fourth reflected light R4 are integrally configured. In this case, a microstructure similar to that of the polarization control element 32 is formed on the surface of the fourth reflective layer R4 on the saturable absorber 4 side. This allows the fourth reflective layer R4 to also function as the polarization control element 32 for the oscillating light. That is, the fourth reflective layer R4 has different transmittances for mutually orthogonal polarized light (e.g., TM wave and TE wave) of the oscillating light of the second wavelength λ2. In this way, the polarization control element 32 and the fourth reflected light R4 are not separate entities but are integrally configured, so the laser device 1 according to the fourth embodiment can be further miniaturized.

[0093] Other configurations of the fourth embodiment may be similar to the corresponding configurations of the second embodiment, and therefore the fourth embodiment can also achieve the effects of the second embodiment.

[0094] (Fifth embodiment) FIG. 6 is a cross-sectional view showing a configuration example of a laser device 1 according to a fifth embodiment. In the fifth embodiment, the fourth reflection layer R4 of the third embodiment also functions as the polarization control element 32. That is, the polarization control element 32 for the oscillating light and the fourth reflected light R4 are integrally configured. In this case, a microstructure similar to that of the polarization control element 32 is formed on the surface of the fourth reflection layer R4 on the saturable absorber 4 side. This allows the fourth reflection layer R4 to also function as the polarization control element 32 for the oscillating light. That is, the fourth reflection layer R4 has different transmittances for mutually orthogonal polarized light (e.g., TM wave and TE wave) of the oscillating light of the second wavelength λ2. Since the polarization control element 32 and the fourth reflected light R4 are not separate entities but are integrally configured, the laser device 1 according to the fifth embodiment can be further miniaturized.

[0095] Other configurations of the fifth embodiment may be similar to the corresponding configurations of the third embodiment, so the fifth embodiment can also achieve the effects of the third embodiment.

[0096] (Sixth embodiment) FIG. 7 is a cross-sectional view showing a configuration example of a laser device 1 according to a sixth embodiment. In the sixth embodiment, the saturable absorber 4 of the second embodiment also functions as the polarization control element 32. That is, the polarization control element 32 for the oscillation light and the saturable absorber 4 are configured as an integrated unit. For example, a microstructure similar to that of the polarization control element 32 is formed on the surface of the saturable absorber 4. This allows the saturable absorber 4 to also function as the polarization control element 32 for the oscillation light. That is, the saturable absorber 4 has different transmittances for mutually orthogonal polarized light (e.g., TM wave and TE wave) of the oscillation light having the second wavelength λ2. Note that, instead of providing a microstructure, the anisotropy of the saturable absorber may be utilized. In this way, the polarization control element 32 and the fourth reflected light R4 are not separate entities but are configured as an integrated unit, so that the laser device 1 according to the sixth embodiment can be further miniaturized.

[0097] Other configurations of the sixth embodiment may be similar to the corresponding configurations of the second embodiment, and therefore the sixth embodiment can also achieve the effects of the second embodiment.

[0098] Seventh embodiment FIG. 8 is a cross-sectional view showing a configuration example of a laser device 1 according to a seventh embodiment. In the seventh embodiment, the saturable absorber 4 of the third embodiment also functions as the polarization control element 32. That is, the polarization control element 32 for the oscillation light and the saturable absorber 4 are configured as an integrated unit. For example, a microstructure similar to that of the polarization control element 32 is formed on the surface of the saturable absorber 4. This allows the saturable absorber 4 to also function as the polarization control element 32 for the oscillation light. That is, the saturable absorber 4 has different transmittances for mutually orthogonal polarized light (e.g., TM wave and TE wave) of the oscillation light having the second wavelength λ2. Note that, instead of providing a microstructure, the anisotropy of the saturable absorber may be utilized. In this way, the polarization control element 32 and the saturable absorber 4 are not separate entities but are configured as an integrated unit, so that the laser device 1 according to the seventh embodiment can be further miniaturized.

[0099] Other configurations of the seventh embodiment may be similar to the corresponding configurations of the third embodiment, so the seventh embodiment can also obtain the effects of the third embodiment.

[0100] (Eighth embodiment) FIG. 9 is a cross-sectional view showing a configuration example of a laser device 1 according to the eighth embodiment. In the eighth embodiment, the fourth reflection layer R4 of the second embodiment also functions as the polarization conversion element 22. That is, the polarization conversion element 22 and the fourth reflection layer R4 are integrally configured. In this case, the saturable absorber 4 is formed, for example, of an anisotropic material, a metasurface structure, a photonic crystal structure, or the like, similar to the polarization conversion element 22. This allows the fourth reflection layer R4 to impart different phase differences to light in oscillation light having mutually orthogonal vibration directions. In this way, the polarization conversion element 22 and the fourth reflection layer R4 are not separate entities but are integrally configured, so the laser device 1 according to the eighth embodiment can be further miniaturized.

[0101] In the eighth embodiment, the polarization control element 31 is provided between the second reflective layer R2 and the polarization conversion element 21. That is, the polarization control element 31 is provided on the opposite side of the solid-state laser medium 3 to the fourth reflective layer R4 having a polarization conversion function. The polarization control element 31 has different transmittances for polarized light beams that are orthogonal to each other in the oscillation light.

[0102] Other configurations of the eighth embodiment may be similar to the corresponding configurations of the second embodiment, and therefore the eighth embodiment can also achieve the effects of the second embodiment.

[0103] (Ninth embodiment) FIG. 10 is a cross-sectional view showing an example of the configuration of a laser device 1 according to the ninth embodiment. In the ninth embodiment, the polarization control element 31 of the third embodiment also functions as the polarization control element 32. That is, the polarization control element 32 for the oscillation light is omitted, and the polarization control element 31 controls the polarization of both the oscillation light and the pumping light. The polarization control element 31 is provided between the second reflected light R2 and the polarization conversion element 21 and is shared by the pumping light resonator 11 and the oscillation light resonator 12. For example, a microstructure that realizes the functions of both the polarization control elements 31 and 32 of the third embodiment is formed on the surface of the polarization control element 31. This allows the polarization control element 31 to control the polarization of both the pumping light and the oscillation light. That is, the polarization control element 31 has a microstructure on its surface that has different transmittances for mutually orthogonal polarizations of the excitation light and different transmittances for mutually orthogonal polarizations of the oscillation light. Because the polarization control element 31 also functions as the polarization control element 32, the laser device 1 according to the ninth embodiment can be further miniaturized.

[0104] Other configurations of the ninth embodiment may be similar to the corresponding configurations of the third embodiment, so the ninth embodiment can also achieve the effects of the third embodiment.

[0105] (Tenth embodiment) FIG. 11 is a cross-sectional view showing an example of the configuration of a laser device 1 according to a tenth embodiment. In the tenth embodiment, the polarization control element 32 of the third embodiment also functions as the polarization control element 31. That is, the polarization control element 31 for the pumping light is omitted, and the polarization control element 32 controls the polarization of both the oscillation light and the pumping light. The polarization control element 32 is provided between the polarization conversion element 22 and the third reflected light R3 and is shared by the pumping light resonator 11 and the oscillation light resonator 12. For example, a microstructure that realizes the functions of both the polarization control elements 31 and 32 of the third embodiment is formed on the surface of the polarization control element 32. This allows the polarization control element 32 to control the polarization of both the pumping light and the oscillation light. That is, the polarization control element 32 has a microstructure on its surface that has different transmittances for mutually orthogonal polarizations of the pumping light and different transmittances for mutually orthogonal polarizations of the oscillation light. Because the polarization control element 32 also functions as the polarization control element 31, the laser device 1 according to the tenth embodiment can be further miniaturized.

[0106] Other configurations of the tenth embodiment may be similar to the corresponding configurations of the third embodiment, so the tenth embodiment can also achieve the effects of the third embodiment.

[0107] (Eleventh embodiment) FIG. 12 is a cross-sectional view showing an example of the configuration of a laser device 1 according to the eleventh embodiment. In the eleventh embodiment, the polarization conversion element 21 of the first embodiment also functions as the polarization control element 31. That is, the polarization control element 31 for the excitation light is omitted, and the polarization conversion element 21 also functions to control the polarization of the excitation light. The polarization conversion element 21 is disposed between the light emitting element 2 and the second reflected light R2, and is provided in the excitation light resonator 11. This allows the polarization conversion element 21 to control the polarization of the excitation light. That is, the polarization conversion element 21 has different transmittances for the mutually orthogonal polarized lights (TM wave and TE wave) of the excitation light. Since the polarization conversion element 21 also functions as the polarization control element 31, the laser device 1 according to the eleventh embodiment can be further miniaturized.

[0108] Other configurations of the eleventh embodiment may be similar to the corresponding configurations of the first embodiment, so the eleventh embodiment can also obtain the effects of the first embodiment.

[0109] (Twelfth embodiment) FIG. 13 is a cross-sectional view showing an example of the configuration of a laser device 1 according to a twelfth embodiment. In the twelfth embodiment, the polarization conversion element 22 of the second embodiment also functions as the polarization control element 32. That is, the polarization control element 32 for the oscillation light is omitted, and the polarization conversion element 22 also functions to control the polarization of the oscillation light. The polarization conversion element 22 is disposed between the saturable absorber 4 and the third reflected light R3, and is provided in the oscillation optical resonator 12. This allows the polarization conversion element 22 to control the polarization of the oscillation light. That is, the polarization conversion element 22 has different transmittances for the mutually orthogonal polarized lights (TM wave and TE wave) of the oscillation light. Since the polarization conversion element 22 also functions as the polarization control element 32, the laser device 1 according to the twelfth embodiment can be further miniaturized.

[0110] Other configurations of the twelfth embodiment may be similar to the corresponding configurations of the second embodiment, and therefore the twelfth embodiment can also obtain the effects of the second embodiment.

[0111] (Thirteenth embodiment) 14 is a cross-sectional view showing an example of the configuration of a laser device 1 according to the thirteenth embodiment. In the thirteenth embodiment, the polarization conversion element 21 of the third embodiment also functions as the polarization control element 31, and the polarization conversion element 22 also functions as the polarization control element 32. That is, the polarization control element 31 for the excitation light and the polarization control element 32 for the oscillation light are omitted. The polarization conversion element 21 also functions to control the polarization of the excitation light, and the polarization conversion element 22 also functions to control the polarization of the oscillation light.

[0112] The polarization conversion element 21 is disposed between the second reflected light R2 and the solid-state laser medium 3, and is shared by the pumping light resonator 11 and the oscillation light resonator 12. This allows the polarization conversion element 21 to control the polarization of the pumping light.

[0113] The polarization conversion element 22 is disposed between the solid-state laser medium 3 and the third reflected light R3, and is shared by the excitation light resonator 11 and the oscillation light resonator 12. This allows the polarization conversion element 22 to control the polarization of the oscillation light.

[0114] Since the polarization conversion elements 21 and 22 also function as the polarization control elements 31 and 32, respectively, the laser device 1 according to the thirteenth embodiment can be further miniaturized.

[0115] Other configurations of the thirteenth embodiment may be similar to the corresponding configurations of the third embodiment, so the thirteenth embodiment can also obtain the effects of the third embodiment.

[0116] [Endoscope system] An example of an endoscopic system will be described with reference to FIGS. 15 and 16. FIG. 15 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. 16 is a diagram illustrating an example of the configuration of an endoscope 5001 and a CCU (Camera Control Unit) 5039. FIG. 15 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. 15, 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.

[0117] 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.

[0118] 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.

[0119] [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. 16 , 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.

[0120] [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. 16 . 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.

[0121] 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).

[0122] [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.

[0123] [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.

[0124] [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.

[0125] [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.

[0126] [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.

[0127] 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.

[0128] [Microscope system] 17 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.

[0129] 17 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.

[0130] 17, during surgery, a microsurgical system 5300 is used to display an enlarged image of the surgical site captured by a microscope device 5301 on a display device 5041 installed in an operating room. The display device 5041 is installed in a position facing an operator 5067, who performs various procedures on the surgical site, such as resecting the affected area, while observing the state of the surgical site using the image displayed on the display device 5041. Microsurgical systems are used, for example, in ophthalmic surgery and brain surgery.

[0131] 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.

[0132] Of the configurations described above, the technology according to the present disclosure can be suitably applied to the surgical tool 5021. Specifically, by irradiating the affected area of ​​a patient with a short laser pulse from the laser element 1 according to this embodiment, the affected area can be treated more safely and reliably without causing damage to the area around the affected area.

[0133] The present technology can be configured as follows. (1) a laminated semiconductor layer having a first reflective layer for a first wavelength and an active layer for surface emitting light of the first wavelength; a laser medium disposed on the rear side of the optical axis of the laminated semiconductor layer, the laser medium having a second reflective layer for a second wavelength on a first surface facing the laminated semiconductor layer and a third reflective layer for the first wavelength on a second surface opposite to the first surface; a fourth reflective layer for the second wavelength, which is disposed on the second surface or on a rear side of the second surface along the optical axis; a first resonator that resonates light of the first wavelength between the first reflective layer and the third reflective layer; a second resonator that resonates light of the second wavelength between the second reflective layer and the fourth reflective layer; a first polarization conversion element provided between the first reflective layer and the laser medium, which changes the phase of light having the first or second wavelength in vibration directions perpendicular to each other; a second polarization conversion element provided between the second reflective layer and the laser medium, which changes the phase of light having the first or second wavelength in a vibration direction perpendicular to the first or second wavelength; at least one of a first and a second polarization control element provided between the first reflective layer and the fourth reflective layer and configured to control polarization of light of the first or second wavelength, The optical axis of the laminated semiconductor layer, the optical axis of the laser medium, the optical axis of the first and second polarization conversion elements, and the optical axis of the first or second polarization control element are arranged on a single axis. (2) The laser element according to (1), wherein the first and second polarization conversion elements are made of an anisotropic material, a metasurface structure, or a photonic crystal structure. (3) The laser element according to (1) or (2), wherein the first and second polarization conversion elements respectively impart a phase difference of approximately a quarter wavelength to light of the first or second wavelength in vibration directions perpendicular to each other. (4) The laser element according to any one of (1) to (3), further comprising a fifth reflective layer provided on the laser medium side of the laminated semiconductor layer. (5) The laser element according to any one of (1) to (4), wherein the first polarization control element is provided between the first reflective layer and the first polarization conversion element and controls the polarization of light of the first wavelength. (6) The laser element according to any one of (1) to (5), wherein the second polarization control element is provided between the fourth reflective layer and the second polarization conversion element and controls the polarization of the light of the second wavelength. (7) A laser element described in any one of (1) to (6), wherein the first polarization control element has a microstructure on its surface so as to have different transmittances for mutually orthogonal polarized light of the first wavelength. (8) The laser element according to any one of (1) to (7), wherein the second polarization control element has a microstructure on its surface so as to have different transmittances for mutually orthogonal polarized light of the second wavelength. (9) The laser element according to any one of (1) to (8), further comprising a saturable absorber provided between the third reflective layer and the fourth reflective layer. (10) the first polarization conversion element is disposed between the first polarization control element and the second reflective layer, The laser element according to any one of (1) to (9), wherein the second polarization conversion element is disposed between the laser medium and the third reflective layer. (11) The laser element according to any one of (1) to (10), wherein the first polarization conversion element is disposed between the second reflection layer and the laser medium, and the second polarization conversion element is disposed between the third reflection layer and the second polarization control element. (12) The laser element according to any one of (1) to (11), wherein the first polarization conversion element is disposed between the second reflective layer and the laser medium, and the second polarization conversion element is disposed between the laser medium and the third reflective layer. (13) The laser element according to any one of (1) to (12), wherein the fourth reflective layer has a microstructure on its surface so as to have different transmittances for mutually orthogonal polarized light of the second wavelength. (14) The laser element according to (9), wherein the saturable absorber has a microstructure on its surface so as to have different transmittances for polarized light of the second wavelength that are orthogonal to each other. (15) The laser element according to any one of (1) to (14), wherein the fourth reflective layer causes a phase difference between light of the second wavelength and light of mutually orthogonal vibration directions. (16) the first polarization control element is provided between the second reflective layer and the first polarization conversion element, The laser element according to any one of (1) to (15), having a microstructure on its surface so as to have different transmittances for mutually orthogonal polarized light of the first wavelength and different transmittances for mutually orthogonal polarized light of the second wavelength. (17) the second polarization control element is provided between the third reflective layer and the second polarization conversion element, A laser element according to any one of (1) to (16), having a microstructure on its surface so as to have different transmittances for polarized light of the first wavelength that is orthogonal to each other, and different transmittances for polarized light of the second wavelength that is orthogonal to each other. (18) The laser element according to any one of (1) to (17), wherein the first polarization conversion element has a microstructure on its surface so as to have different transmittances for mutually orthogonal polarized light of the first wavelength. (19) The laser element according to any one of (1) to (18), wherein the second polarization conversion element has a microstructure on its surface so as to have different transmittances for mutually orthogonal polarized light of the second wavelength. (20) The laser element according to any one of (1) to (19), wherein the laminated semiconductor layer, the laser medium, the fourth reflection layer, the first resonator, the second resonator, the first polarization conversion element, the second polarization conversion element, and the first or second polarization control element are integrally bonded. (twenty one) The laser element according to any one of (1) to (20), further comprising a transparent member provided somewhere between the first reflective layer and the fourth reflective layer. (twenty two) An electronic device comprising a laser element and a control unit that controls the emission of light from the laser element, The laser element is a laminated semiconductor layer having a first reflective layer for a first wavelength and an active layer for surface emitting light of the first wavelength; a laser medium disposed on the rear side of the optical axis of the laminated semiconductor layer, the laser medium having a second reflective layer for a second wavelength on a first surface facing the laminated semiconductor layer and a third reflective layer for the first wavelength on a second surface opposite to the first surface; a fourth reflective layer for the second wavelength, which is disposed on the second surface or on a rear side of the second surface along the optical axis; a first resonator that resonates light of the first wavelength between the first reflective layer and the third reflective layer; a second resonator that resonates light of the second wavelength between the second reflective layer and the fourth reflective layer; a first polarization conversion element provided between the first reflective layer and the laser medium, which changes the phase of light of the first wavelength in vibration directions orthogonal to each other; a second polarization conversion element provided between the second reflective layer and the laser medium, which changes the phase of light of the second wavelength in vibration directions orthogonal to each other; at least one of a first and a second polarization control element provided between the first reflective layer and the fourth reflective layer and configured to control polarization of light of the first or second wavelength, an optical axis of the laminated semiconductor layer, an optical axis of the laser medium, an optical axis of the first and second polarization conversion elements, and an optical axis of the first or second polarization control element are arranged on a single axis;

[0134] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present disclosure. Furthermore, the effects described in this specification are merely examples and are not intended to be limiting, and other effects may also be obtained. [Explanation of symbols]

[0135] 2 Light-emitting element, 5 Substrate, R5 Fifth reflective layer, 6 Cladding layer, 7 Active layer, 8 Cladding layer, 11 Excitation optical resonator, 12 Oscillation optical resonator, R1 First reflective layer, R2 Second reflective layer, R3 Third reflective layer, R4 Fourth reflective layer, 1 Laser element, 21, 22 Polarization conversion element, 31 Polarization control element, 4 Saturable absorber

Claims

1. a laminated semiconductor layer including a first reflective layer for a first wavelength and an active layer for surface emitting light of the first wavelength; a laser medium disposed on the rear side of the laminated semiconductor layer with respect to the optical axis, the laser medium having a second reflective layer for a second wavelength on a first surface facing the laminated semiconductor layer and a third reflective layer for the first wavelength on a second surface opposite to the first surface; a fourth reflective layer for the second wavelength, the fourth reflective layer being disposed on the second surface or on a rear side of the second surface along the optical axis; a first resonator that resonates light of the first wavelength between the first reflective layer and the third reflective layer; a second resonator that resonates light of the second wavelength between the second reflective layer and the fourth reflective layer; a first polarization conversion element provided between the first reflective layer and the laser medium, which changes the phase of light having the first or second wavelength in vibration directions orthogonal to each other; a second polarization conversion element provided between the fourth reflective layer and the laser medium, which changes the phase of light having the first or second wavelength in a vibration direction perpendicular to the first or second wavelength; at least one of a first polarization control element and a second polarization control element that is provided between the first reflection layer and the fourth reflection layer and that controls polarization of light of the first wavelength or the second wavelength, A laser element, wherein the optical axis of the laminated semiconductor layer, the optical axis of the laser medium, the optical axis of the first and second polarization conversion elements, and the optical axis of the first or second polarization control element are arranged on a single axis.

2. The laser element according to claim 1 , wherein the first and second polarization conversion elements are made of an anisotropic material, a metasurface structure, or a photonic crystal structure.

3. 2. The laser element according to claim 1, wherein the first and second polarization conversion elements respectively impart a phase difference of approximately a quarter wavelength to light of the first and second wavelengths vibrating in directions orthogonal to each other.

4. The laser device according to claim 1 , further comprising a fifth reflective layer provided on the laser medium side of the laminated semiconductor layer.

5. 2. The laser element according to claim 1, wherein the first polarization control element is provided between the first reflective layer and the first polarization conversion element, and controls polarization of the light of the first wavelength.

6. 2. The laser element according to claim 1, wherein the second polarization control element is provided between the fourth reflective layer and the second polarization conversion element, and controls the polarization of the light of the second wavelength.

7. The laser device according to claim 1 , wherein the first polarization control element has a microstructure on a surface thereof so as to have different transmittances for mutually orthogonal polarized light beams of the first wavelength.

8. The laser device according to claim 1 , wherein the second polarization control element has a microstructure on a surface thereof so as to have different transmittances for mutually orthogonal polarized light beams of the second wavelength.

9. The laser device according to claim 1 , further comprising a saturable absorber provided between the third reflective layer and the fourth reflective layer.

10. the first polarization conversion element is disposed between the first polarization control element and the second reflective layer, The laser device according to claim 1 , wherein the second polarization conversion element is disposed between the laser medium and the third reflective layer.

11. 2. The laser element according to claim 1, wherein the first polarization conversion element is disposed between the second reflective layer and the laser medium, and the second polarization conversion element is disposed between the third reflective layer and the second polarization control element.

12. 2. The laser element according to claim 1, wherein the first polarization conversion element is disposed between the second reflective layer and the laser medium, and the second polarization conversion element is disposed between the laser medium and the third reflective layer.

13. The laser device according to claim 1 , wherein the fourth reflective layer has a microstructure on a surface thereof so as to have different transmittances for mutually orthogonal polarized light beams of the second wavelength.

14. 10. The laser device according to claim 9, wherein the saturable absorber has a microstructure on its surface so as to have different transmittances for polarized light of the second wavelength that are orthogonal to each other.

15. The laser element according to claim 1 , wherein the fourth reflective layer causes a phase difference between light of the second wavelength and light of mutually orthogonal vibration directions.

16. the first polarization control element is provided between the second reflective layer and the first polarization conversion element, 2. The laser element according to claim 1, having a microstructure on its surface so as to have different transmittances for mutually orthogonal polarized light of the first wavelength and different transmittances for mutually orthogonal polarized light of the second wavelength.

17. the second polarization control element is provided between the third reflective layer and the second polarization conversion element, 2. The laser element according to claim 1, having a microstructure on its surface so as to have different transmittances for mutually orthogonal polarized light of the first wavelength and different transmittances for mutually orthogonal polarized light of the second wavelength.

18. The laser element according to claim 1 , wherein the first polarization conversion element has a microstructure on a surface thereof so as to have different transmittances for mutually orthogonal polarized light beams of the first wavelength.

19. The laser element according to claim 1 , wherein the second polarization conversion element has a microstructure on a surface thereof so as to have different transmittances for mutually orthogonal polarized light beams of the second wavelength.

20. 2. The laser element according to claim 1, wherein the laminated semiconductor layer, the laser medium, the fourth reflective layer, the first resonator, the second resonator, the first polarization conversion element, the second polarization conversion element, and the first or second polarization control element are integrally bonded.

21. The laser device according to claim 1 , further comprising a transparent member provided somewhere between the first reflective layer and the fourth reflective layer.

22. An electronic device comprising a laser element and a control unit that controls the emission of light from the laser element, The laser element is a laminated semiconductor layer including a first reflective layer for a first wavelength and an active layer for surface emitting light of the first wavelength; a laser medium disposed on the rear side of the laminated semiconductor layer with respect to the optical axis, the laser medium having a second reflective layer for a second wavelength on a first surface facing the laminated semiconductor layer and a third reflective layer for the first wavelength on a second surface opposite to the first surface; a fourth reflective layer for the second wavelength, the fourth reflective layer being disposed on the second surface or on a rear side of the second surface along the optical axis; a first resonator that resonates light of the first wavelength between the first reflective layer and the third reflective layer; a second resonator that resonates light of the second wavelength between the second reflective layer and the fourth reflective layer; a first polarization conversion element provided between the first reflective layer and the laser medium, which changes the phase of light of the first wavelength in vibration directions orthogonal to each other; a second polarization conversion element provided between the fourth reflective layer and the laser medium, which changes the phase of light of the second wavelength in vibration directions orthogonal to each other; at least one of a first polarization control element and a second polarization control element that is provided between the first reflection layer and the fourth reflection layer and that controls polarization of light of the first wavelength or the second wavelength, an optical axis of the laminated semiconductor layer, an optical axis of the laser medium, an optical axis of the first and second polarization conversion elements, and an optical axis of the first or second polarization control element are arranged on a single axis.

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