Laser elements and electronic devices

Abstract

[Problem] To improve the excitation light output without generating heat or causing a decrease in the service life. [Solution] A laser element according to the present invention is provided with: a multilayer semiconductor layer which comprises a first reflective layer with respect to light having a first wavelength and an active layer that performs surface emission of light having the first wavelength; a second reflective layer with respect to light having the first wavelength, the second reflective layer being arranged closer to the light exit surface than the multilayer semiconductor layer; and a polarization splitting element which multiplexes polarized light beams that are contained in the light emitted from the multilayer semiconductor layer and are perpendicular to each other by causing the polarized light beams to separately resonate between the first reflective layer and the second reflective layer.

Description

[Technical Field]

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

[0002] Laser technology is applied in various fields such as microfabrication, medical equipment, and distance measurement. In particular, short-pulse laser technology is expected to be applied to high-precision processing technology and highly efficient wavelength conversion technology. Among these, Q-switched solid-state lasers are used in a wide range of applications because they can obtain high peak power exceeding kW (kilowatts) with a relatively simple configuration (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication WO2021 / 106757A1 Summary of the Invention [Problem to be solved by the invention]

[0004] A multi-junction structure has been proposed, in which multiple active layers are provided inside a pump light source made of laminated semiconductor layers. This type of pump light source has a higher thermal resistance than an EEL (Edge Emitting Laser), and there is an upper limit (rollover point) to the optical output. Therefore, if you try to increase the optical output by increasing the power of the pump light source, the junction temperature rises, and the long-term reliability of the device (MTTF: Mean Time To Failure) decreases.

[0005] Patent Document 1 discloses a structure in which a laminated semiconductor layer is combined with a solid-state laser medium for Q-switching. A first resonator, which is an excitation light source and is composed of a laminated semiconductor layer and a solid-state laser medium, and a second resonator, which is composed of a solid-state laser medium and a saturable absorber, are adjacent to each other, enabling high-intensity excitation of the solid-state laser medium within the first resonator.

[0006] The average output of the Q-switched light can be increased by spatially combining it using an optical lens or by combining it using polarization. However, the waveform of the Q-switched light generated by the pump light source contains jitter, so combining it does not improve the total peak power. On the other hand, even if you try to increase the optical output of the pump light source, for the reasons mentioned above, the upper limit of the peak intensity of the Q-switched light is determined by the limit of the pump light output.

[0007] Therefore, the present disclosure provides a laser element and an electronic device that can improve the excitation light output without generating heat or shortening the lifespan. [Means for solving the problem]

[0008] In order to solve the above problems, according to the present disclosure, there is provided a semiconductor device including: a laminated semiconductor layer having a first reflective layer for light of a first wavelength and an active layer that performs surface emission of the first wavelength; a second reflective layer for light of the first wavelength, the second reflective layer being disposed closer to the light emitting surface than the laminated semiconductor layer; A laser element is provided, which includes a polarization separation element that individually resonates each of the orthogonal polarized light beams contained in the light emitted from the laminated semiconductor layer between the first reflective layer and the second reflective layer to combine them.

[0009] the laminated semiconductor layer has a plurality of laminated semiconductor regions corresponding to the orthogonally polarized light, The polarization separation element may individually resonate corresponding polarized light between the first reflective layer and the second reflective layer for each of the plurality of laminated semiconductor regions, and combine the light.

[0010] The polarization separation element may have a first surface that is in contact with the light exit surface of the laminated semiconductor layer, and a second surface that is positioned between the first reflective layer and the second reflective layer on the opposite side of the first surface.

[0011] the orthogonally polarized light includes orthogonally polarized light of different wavelengths, The polarization separation element may cause each of the orthogonal polarized light beams containing orthogonal polarized light beams of different wavelengths to resonate individually between the first reflective layer and the second reflective layer and combine them.

[0012] the orthogonally polarized light includes TM (Transverse Magnetic) polarized light and TE (Transverse Electric) polarized light, The polarization separation element may couple the TE polarized light and the TM polarized light by individually resonating them between the first reflecting layer and the second reflecting layer.

[0013] The polarization separation element may combine the TE polarized light with the TM polarized light inside the polarization separation element.

[0014] the polarization separation element has a laminate in which a plurality of polarization separation films and a plurality of reflective films are alternately stacked at intervals, the laminate has a cut surface cut at an angle of 45 degrees to the normal direction of the laminate surface, The polarization separation element may be disposed so that the normal direction of the cut surface is parallel to the normal direction of the laminated semiconductor layers.

[0015] The polarization separation element may include a birefringent material that separates the light emitted from the laminated semiconductor layer into the orthogonally polarized light beams.

[0016] The laser may further include a laser medium that is disposed closer to the light exit surface than the polarization separation element and that resonates at a second wavelength different from the first wavelength.

[0017] a third reflective layer for light of the second wavelength, the third reflective layer being disposed on a first end surface of the laser medium on the polarization separation element side; The laser medium may further include a fourth reflective layer for the light of the second wavelength, the fourth reflective layer being disposed on a second end face of the laser medium opposite to the first end face.

[0018] The third reflective layer may be disposed closer to the light exit surface than the second reflective layer.

[0019] The third reflective layer may be disposed between the polarisation separation element and the second reflective layer.

[0020] The third reflective layer may be in contact with an end face of the polarization separation element.

[0021] The fourth reflective layer may be in contact with the second reflective layer or may be disposed closer to the light exit surface than the second reflective layer.

[0022] The laser may further include a saturable absorber disposed closer to the light output surface than the laser medium.

[0023] a third reflective layer for light of the second wavelength, the third reflective layer being disposed on an end surface of the laser medium facing the polarization separation element; The optical fiber may further include a fourth reflecting layer for the light of the second wavelength, the fourth reflecting layer being disposed on the light exit surface side of the saturable absorber.

[0024] The third reflective layer may be disposed closer to the light exit surface than the second reflective layer.

[0025] The second reflective layer may be disposed between the third reflective layer and the fourth reflective layer.

[0026] Each of the laminated semiconductor layer, the polarization separation element, the laser medium, and the saturable absorber may be divided into a plurality of regions corresponding to a plurality of light-emitting units that emit pulsed laser light of the second wavelength and are arranged at predetermined intervals.

[0027] According to the present disclosure, a laser element; a control unit that controls the emission of light from the laser element, The laser element is a laminated semiconductor layer having a first reflective layer for light of a first wavelength and an active layer for surface emitting light of the first wavelength; a second reflective layer for light of the first wavelength, the second reflective layer being disposed closer to the light emitting surface than the laminated semiconductor layer; An electronic device is provided, which includes a polarization separation element that individually resonates each of a plurality of polarized light beams contained in the light emitted from the laminated semiconductor layer between the first reflective layer and the second reflective layer to combine them. [Brief explanation of the drawings]

[0028] [Figure 1] FIG. 1 is a schematic cross-sectional view of a laser element according to a first embodiment. [Figure 2] 1A and 1B are a schematic cross-sectional view and a plan view seen from the light emitting surface side of a laser element according to a comparative example; [Figure 3] 3 is a diagram showing the relationship between the current of the pumping light source and the optical output of the laser device of FIG. 2. [Figure 4] FIG. 4 is a schematic cross-sectional view of a laser element according to a second embodiment. [Figure 5] 5A to 5C are diagrams schematically showing a method for manufacturing a polarization separation element. [Figure 6A] FIG. 10 is a diagram showing an example in which TM polarized light and TE polarized light are combined at approximately the center in the thickness direction of a polarization separation element. [Figure 6B] FIG. 10 is a diagram showing an example in which TM polarized light and TE polarized light are combined at a location shifted from the center in the thickness direction of a polarization separation element. [Figure 7] FIG. 10 is a schematic cross-sectional view of a laser element according to a third embodiment. [Figure 8] 10A and 10B are diagrams showing design examples of a polarization separation film. [Figure 9] FIG. 10 is a schematic cross-sectional view of a laser element according to a fourth embodiment. [Figure 10] FIG. 10 is a schematic cross-sectional view of a laser element according to a fifth embodiment. [Figure 11] FIG. 10 is a schematic cross-sectional view of a laser element according to a sixth embodiment. [Figure 12] FIG. 13 is a schematic cross-sectional view of a laser element according to a seventh embodiment. [Figure 13] FIG. 13 is a schematic cross-sectional view of a laser element according to an eighth embodiment. [Figure 14] FIG. 14 is a schematic cross-sectional view showing the layers of the laser device of FIG. 13 in more detail. [Figure 15] 3A and 3B are a plan view and a cross-sectional view showing a plurality of laser elements arranged in an array. [Figure 16A] 1 is a cross-sectional view of a laser gain element according to the present disclosure; [Figure 16B] 1 is a perspective view of a laser gain element according to the present disclosure; [Figure 16C] FIG. 2 is a plan view schematically showing the optical path of laser light within the laser amplifier element. [Figure 17] FIG. 1 is a diagram showing an example of a schematic configuration of an endoscope system. [Figure 18] FIG. 18 is a block diagram showing an example of the functional configuration of the camera and the CCU shown in FIG. 17. [Figure 19] FIG. 1 is a diagram showing an example of a schematic configuration of a microsurgery system. DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, embodiments of a laser element and electronic equipment will be described with reference to the drawings. The following description will focus on the main components of the laser element and electronic equipment, but the laser element and electronic equipment may include components and functions that are not shown or described. The following description does not exclude components and functions that are not shown or described.

[0030] (First embodiment) Fig. 1 is a schematic cross-sectional view of a laser device 1 according to the first embodiment. As shown in Fig. 1, the laser device 1 according to the first embodiment includes an excitation light source 2 having a first reflective layer R1 and an active layer, a second reflective layer R2, and a polarization separation element 10.

[0031] The laser device 1 according to the first embodiment is an integrated laminated structure that can be fabricated using semiconductor process technology, and therefore has excellent mass productivity and stability of laser output.

[0032] The excitation light source 2 is a laminated semiconductor layer. Hereinafter, the excitation light source 2 may be referred to as the laminated semiconductor layer 2. The laminated semiconductor layer 2 is a form of a vertical cavity surface emitting laser (VCSEL). What differs from a VCSEL is that a second reflective layer R2, which is at least one of the mirrors constituting the resonator, is provided outside the laminated semiconductor layer 2, which is the main body of the excitation light source 2. The second reflective layer R2 is, for example, an external resonator mirror. The laminated semiconductor layer 2 is also called a VECSEL (Vertical External-Cavity Surface Emitting Laser).

[0033] The laminated semiconductor layer 2 has a first reflective layer R1 for light of the first wavelength λ1 and an active layer that performs surface emission of the first wavelength λ1. A detailed layer configuration of the laminated semiconductor layer 2 will be described later. The second reflective layer R2 is arranged closer to the light emission surface than the laminated semiconductor layer 2. The first reflective layer R1 and the second reflective layer R2 form a first resonator 11 that resonates light of the first wavelength λ1.

[0034] The polarization separation element 10 is a flat element that is provided between the first resonators 11 and that polarizes and separates light from the excitation light source 2. The polarization separation element 10 combines orthogonal polarized light beams while uniquely determining the polarization direction. That is, the polarization separation element 10 combines orthogonal polarized light beams included in the light emitted from the laminated semiconductor layer 2 that constitutes the excitation light source 2 by individually resonating each of the orthogonal polarized light beams between the first reflection layer R1 and the second reflection layer R2. The internal structure of the polarization separation element 10 is not important. One specific example of the polarization separation element 10 is a PBS (Polarizing Beam Splitter). For example, by providing a first optical member 13 that transmits the first polarized light and reflects the second polarized light, and a second optical member 14 that reflects the second polarized light inside the polarization separation element 10, the first polarized light passes through the first optical member 13 and resonates between the first reflective layer R1 and the second reflective layer R2, and the second polarized light is reflected by the second optical member 14 and the first optical member 13 and resonates between the first reflective layer R1 and the second reflective layer R2.

[0035] The polarization separation element 10 has a first surface that is in contact with the light-emitting surface of the laminated semiconductor layer 2, and a second surface that is disposed between the first reflecting layer and the second reflecting layer on the opposite side of the first surface.

[0036] Fig. 2 shows a schematic cross-sectional view of a laser device 100 according to a comparative example, and a plan view seen from the light-emitting surface side. The laser device 100 in Fig. 2 has a configuration in which an excitation light source 2 made of a laminated semiconductor layer 2, a solid-state laser medium 3 for Q-switching, and a saturable absorber 4 are arranged in this order. A uniform material layer 15 that does not control polarization may be arranged between the excitation light source 2 and the solid-state laser medium 3. This material layer 15 may be, for example, a support substrate that supports the excitation light source 2.

[0037] The laser device 100 in Fig. 2 has a first resonator 11 that resonates at a first wavelength λ1 and a second resonator 12 that resonates at a second wavelength λ2. The second resonator 12 is also called a Q-switched solid-state laser resonator. The solid-state laser medium 3 in Fig. 2 is used in either the first resonator 11 or the second resonator 12. The first resonator 11 performs a resonant operation between the pumping light source 2 and the solid-state laser medium 3, and the second resonator 12 performs a resonant operation between the solid-state laser medium 3 and the saturable absorber 4.

[0038] The solid-state laser medium 3 is excited by light of the first wavelength λ1 that is emitted from the excitation light source 2 and resonated in the first resonator 11. When the power of the excitation light of the first wavelength λ1 accumulates in the solid-state laser medium 3 and the solid-state laser medium 3 reaches a sufficiently excited state, the light absorption rate in the saturable absorber 4 drops sharply, and the second resonator 12 resonates the light of the second wavelength λ2 between the third and fourth reflecting layers, causing the Q-switched laser pulse to be emitted from the saturable absorber 4. FIG. 2 shows an example in which the shape of the light emitting portion 20 is circular.

[0039] The pumping light source 2 in Figure 2 is composed of a laminated semiconductor layer 2, so the volume of the active layer within the laminated semiconductor layer 2 is limited. A multi-junction structure has also been proposed, in which multiple active layers are provided within the laminated semiconductor layer 2. However, the pumping light source 2 in Figure 2 has poorer thermal conductivity than an edge-emitting laser, and the volume of the active layer is small, so the optical output cannot be increased. If an attempt is made to increase the optical output by increasing the power of the pumping light source 2, the junction temperature rises, significantly shortening the life of the laser element 1.

[0040] Fig. 3 is a diagram showing the relationship between the current and optical output of the pumping light source 2 in the laser device 100 of Fig. 2. As shown in Fig. 3, when the current flowing through the pumping light source 2 reaches a predetermined value, the optical output reaches an upper limit, and if the current is increased beyond that, the junction temperature rises and the optical output decreases.

[0041] The light emitted from the excitation light source 2 contains multiple polarized lights, but the first resonator 11 performs a random resonation operation regardless of the type of polarized light. Only the energy of the light is transmitted from the first resonator 11 to the second resonator 12 without selecting a specific polarized light.

[0042] 1, the laminated semiconductor layer 2 constituting the pumping light source 2 is divided into a plurality of laminated semiconductor regions corresponding to orthogonal polarized light beams contained in the light emitted from the pumping light source 2. The plurality of laminated semiconductor regions emit unpolarized spontaneous emission light. The polarization separation element 10 individually resonates the corresponding polarized light beams between the first reflective layer R1 and the second reflective layer R2 for each of the plurality of laminated semiconductor regions, thereby combining the corresponding polarized light beams.

[0043] 1, for example, each of the two types of polarized light undergoes a separate resonant operation between the first reflective layer R1 and the second reflective layer R2, so that the optical output emitted from the polarization separation element 10 can be approximately twice that of Fig. 2. The ability to improve the optical output emitted from the polarization separation element 10 means that high optical output can be maintained even if the current flowing through the excitation light source 2 is reduced compared to the laser element 100 of Fig. 2, and since the current flowing through the excitation light source 2 can be reduced, the life of the laser element 1 can be extended.

[0044] 1 can be formed into an integrated structure by a semiconductor process, which improves mass productivity, increases the pumping light output by combining pumping lights from multiple stacked semiconductor regions, and improves the long-term reliability (MTTF: Mean Time To Failure) of the laser device 1.

[0045] As described above, in the first embodiment, the orthogonal polarized light beams included in the light emitted from the laminated semiconductor layer 2 are resonated between the first reflective layer R1 and the second reflective layer R2 and combined, thereby increasing the pumping light output without increasing the current flowing through the pumping light source 2. The pumping light source 2 is, for example, a semiconductor laser. The polarization separation element 10 is stacked within the first resonator 11 using the semiconductor laser, and the polarized light beams separated within the polarization separation element 10 are combined, so that the pumping light output can be improved even with a small laser element 1. Furthermore, since the pumping light output can be maintained high even when the current flowing through the pumping light source 2 is reduced, the life of the laser element 1 can be extended.

[0046] (Second embodiment) Fig. 4 is a schematic cross-sectional view of a laser device 1a according to the second embodiment. In the laser device 1a of Fig. 4, the orthogonal polarized light contained in the light emitted from the laminated semiconductor layer 2 includes TM (Transverse Magnetic) polarized light and TE (Transverse Electric) polarized light. The polarization separation element 10 resonates the TE polarized light and the TM polarized light separately between the first reflective layer R1 and the second reflective layer R2, and combines them.

[0047] One example of the polarization splitter element 10 is a polarization conversion element (PS converter). Polarization conversion elements can be manufactured using the same manufacturing method as those generally used in liquid crystal projectors. Polarization conversion elements for liquid crystal projectors have an opening window disposed on the entrance surface and a half-wave plate disposed on the exit surface, but the polarization conversion element of this embodiment does not require an opening window or a half-wave plate, and instead has a polarization splitter film 16 disposed on the combining surface.

[0048] The polarization splitter element 10 has a configuration in which polarization splitter films 16 and reflective films 17 are arranged alternately along the light incident surface, with the films tilted 45 degrees relative to the normal to the light incident surface. The polarization splitter film 16 transmits TM polarized light but reflects TE polarized light. The reflective film 17 reflects TE polarized light. Therefore, by arranging the polarization splitter film 16 and the reflective film 17 side by side along the light incident surface, the TM polarized light resonates between the first reflective layer R1 and the second reflective layer R2 along the normal to the end face of the polarization splitter element 10. The TE polarized light resonates between the first reflective layer R1 and the second reflective layer R2 while being reflected by the reflective film 17 and the polarization splitter film 16. The TE polarized light is reflected by the reflective film 17 and is combined with the TM polarized light when further reflected by the polarization splitter film 16. This increases the excitation light output from the polarization splitter film 16.

[0049] In the laser device 1a according to the second embodiment, even if the distance between the polarization separation film 16 and the reflective film 17 is 1 mm or more, the TM polarized light and the TE polarized light can be multiplexed.

[0050] 5 is a diagram schematically illustrating a method for manufacturing the polarization separation element 10. A first substrate 22 having a polarization separation film 16 formed on the end face of a base layer 21 and a second substrate 24 having a reflective film 17 formed on the end face of a base layer 23 are alternately stacked to form a laminate 25. There is no particular restriction on the material of the base layers 21 and 23, but the material must not have a polarization separation function.

[0051] Next, the laminate 25 is cut at an inclination angle of 45 degrees relative to the normal direction of the substrate surface, as shown by the two-dot chain line in FIG. 5, to produce a plurality of polarization separation elements 10 each made up of a plurality of laminates 25.

[0052] If the thickness of each of the first substrates 22 and second substrates 24 constituting the laminate 25 is highly accurate, the optical axes of the combined light will coincide. Even if misalignment occurs in the surface direction of the substrates during bonding, the resulting polarization separation element 10 is robust enough to prevent misalignment of the optical path.

[0053] Figure 6A shows an example in which TM polarized light and TE polarized light are combined at approximately the center of the thickness direction of the polarization separation element 10, and Figure 6B shows an example in which TM polarized light and TE polarized light are combined at a location shifted from the center of the thickness direction of the polarization separation element 10.

[0054] 6A and 6B, the multiplexing positions of the TM polarized light and the TE polarized light are different due to the misalignment of the polarization splitting film 16 and the reflective film 17 in the substrate surface direction within the polarization splitting element 10, but the optical paths of the TM polarized light and the TE polarized light after multiplexing are not misaligned, thereby improving robustness.

[0055] In this way, in the second embodiment, by using a polarization separation element 10 in which polarization separation films 16 and reflective films 17 are arranged alternately along the light incident surface, with the polarization separation films 16 and reflective films 17 being inclined at 45 degrees from the normal direction of the substrate surface, the TM polarized light and TE polarized light contained in the excitation light can be combined inside the polarization separation element 10, thereby increasing the excitation light output.

[0056] (Third embodiment) Fig. 7 is a schematic cross-sectional view of a laser device 1b according to the third embodiment. The laser device 1b in Fig. 7 is different from the laser devices 1 and 1a according to the first and second embodiments in the internal structure of the polarization separation element 10.

[0057] The polarization separation element 10 according to the third embodiment includes a polarization separation film 16 and multiple reflective films 17a and 17b. The multiple reflective films 17a and 17b reflect TE polarized light of different wavelengths. The polarization separation element 10 shown in FIG. 7 includes a polarization separation film 16, a first reflective film 17a that reflects TE polarized light of wavelength λ1, and a second reflective film 17b that reflects TE polarized light of wavelength λ2.

[0058] 8 shows an example design of the polarization separation film 16, with the horizontal axis representing wavelength and the vertical axis representing transmittance. By changing the reflection characteristics of the first reflection film 17a and the second reflection film 17b, it is possible to adjust the wavelength band of the excitation light emitted from the polarization separation element 10, thereby further improving the output of the excitation light.

[0059] (Fourth embodiment) FIG. 9 is a schematic cross-sectional view of a laser device 1c according to a fourth embodiment. While the laser devices 1a and 1b in FIGS. 4 and 7 have a polarization separation element 10 in which polarization separation films 16 and reflective films 17 are alternately arranged, the laser device 1c in FIG. 9 has a polarization separation element 10 made of a birefringent material. A birefringent material is a material that separates incident light into orthogonal polarized light beams depending on the polarization state of the incident light. A birefringent material typically separates incident light into two polarized light beams. One of the two polarized light beams is called ordinary light (ordinary light) and the other is called extraordinary light.

[0060] Figure 9 shows an example in which, of two polarized lights separated by a birefringent material, TM polarized light is ordinary light and TE polarized light is extraordinary light. The TM polarized light resonates between the first reflective layer R1 and the second reflective layer R2 along the normal direction to the substrate surface. The TE polarized light travels obliquely through the birefringent material and is combined with the TM polarized light, causing resonance between the first reflective layer R1 and the second reflective layer R2.

[0061] Examples of birefringent materials include rutile, which is a titanium dioxide (TiO2) crystal, yttrium vanadate (YVO4) crystal, lithium niobate (LiNbO3) crystal, and quartz. The specific type of birefringent material is not important. A material that has high transmittance for the wavelength of the excitation light emitted from the excitation light source 2 and is easy to process so that precision in the C-axis direction can be achieved is desirable.

[0062] Rutile crystal is a birefringent material with high birefringence, and the transmitted light can be separated into ordinary and extraordinary rays. The polarization state of the extraordinary rays is orthogonal to that of the ordinary rays. The alignment accuracy of the excitation light source 2 and the polarization separation element 10 can be further improved by cutting out the crystal with precision.

[0063] As described above, in the fourth embodiment, the polarization separation element 10 is formed of a birefringent material, which simplifies the internal structure of the polarization separation element 10 and the manufacturing process. On the other hand, in order to combine TM polarized light and TE polarized light inside the polarization separation element 10, it is necessary to optimize the thickness of the polarization separation element 10 and the birefringent material.

[0064] (Fifth embodiment) Fig. 10 is a schematic cross-sectional view of a laser device 1d according to a fifth embodiment. The laser device 1d in Fig. 10 has a configuration in which a solid-state laser medium 3 is provided in the laser device 1, 1a, 1b, or 1c according to any one of the first to fourth embodiments. The solid-state laser medium 3 in Fig. 10 is arranged closer to the light output surface than the polarization separation element 10. For example, the solid-state laser medium 3 is arranged closer to the light output surface than the second reflective layer R2.

[0065] The solid-state laser medium 3 resonates at a second wavelength λ2 different from the first wavelength λ1. The solid-state laser medium 3 has a third reflective layer R3 disposed on a first end face and a fourth reflective layer R4 disposed on a second end face opposite the first end face. The third reflective layer R3 and the fourth reflective layer R4 reflect light of the second wavelength λ2. Therefore, the light of the second wavelength λ2 resonates between the third reflective layer R3 and the fourth reflective layer R4.

[0066] 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.

[0067] The solid-state laser medium 3 is not limited to Yb:YAG, and for example, at least one of Nd:YAG, Nd:YVO4, Nd:YLF, Nd:glass, Yb:YAG, Yb:YLF, Yb:FAP, Yb:SFAP, Yb:YVO, Yb:glass, Yb:KYW, Yb:BCBF, Yb:YCOB, Yb:GdCOB, and YB:YAB can be used as the solid-state laser medium 3. The form is not limited to crystal, and ceramic materials can also be used.

[0068] Furthermore, the solid-state laser medium 3 may be a four-level solid-state laser medium 3 or a quasi-three-level solid-state laser medium 3. However, since the appropriate pumping wavelength (first wavelength λ1) differs depending on the crystal, it is necessary to select the semiconductor material of the active layer in the pumping light source 2 according to the material of the solid-state laser medium 3.

[0069] In this way, in the fifth embodiment, the solid-state laser medium 3 is disposed closer to the light exit surface than the polarization separation element 10, so that wavelength conversion of the emitted light can be performed. The laser element 1d according to the fifth embodiment can also be formed by a semiconductor process, which improves mass productivity.

[0070] (Sixth embodiment) The laser device according to the sixth embodiment has a saturable absorber provided closer to the light output surface than the solid-state laser medium 3.

[0071] Fig. 11 is a schematic cross-sectional view of a laser device 1e according to a sixth embodiment. The laser device 1e in Fig. 11 has a configuration in which a solid-state laser medium 3 and a saturable absorber 4 are provided in addition to the laser devices 1 to 1c according to any of the first to fourth embodiments. The solid-state laser medium 3 in Fig. 11 is arranged closer to the light output surface than the polarization separation element 10, and the saturable absorber 4 is arranged closer to the light output surface than the solid-state laser medium 3.

[0072] The solid-state laser medium 3 and the saturable absorber 4 resonate at a second wavelength λ2 different from the first wavelength λ1. A third reflecting layer R3 for light of the second wavelength λ2 is provided on the end face of the solid-state laser medium 3 facing the polarization separation element 10. A fourth reflecting layer R4 for light of the second wavelength λ2 is provided on the light exit surface side of the saturable absorber 4. The third reflecting layer R3 and the fourth reflecting layer R4 reflect the light of the second wavelength λ2. Therefore, the light of the second wavelength λ2 resonates between the third reflecting layer R3 and the fourth reflecting layer R4.

[0073] 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.

[0074] In this way, in the sixth embodiment, the solid-state laser medium 3 and the saturable absorber 4 are arranged in this order on the light output surface side of the polarization separation element 10, so that a jitter-free Q-switched pulse can be emitted using the excitation light that has been combined by the polarization separation element 10 and has improved optical output.

[0075] (Seventh embodiment) In the laser device according to the seventh embodiment, the solid-state laser medium 3 is shared by the first resonator 11 and the second resonator 12.

[0076] Fig. 12 is a schematic cross-sectional view of a laser device 1f according to a seventh embodiment. The laser device 1f of Fig. 12 includes a solid-state laser medium 3 arranged on the light-emitting surface side of a polarization separation element 10. A first reflection layer R1 is arranged on the end face opposite to the light-emitting surface of the laminated semiconductor layer 2, which is the excitation light source 2. A third reflection layer R3 is arranged between the polarization separation element 10 and the solid-state laser medium 3. A second reflection layer R2 and a fourth reflection layer R4 are arranged on the light-emitting surface side of the solid-state laser medium 3.

[0077] The laser device 1f of Fig. 12 includes a first resonator 11 and a second resonator 12. The first resonator 11 resonates light of a first wavelength λ1 between the first reflective layer R1 and the second reflective layer R2. The second resonator 12 resonates light of a second wavelength λ2 between the third reflective layer R3 and the fourth reflective layer R4. Therefore, the solid-state laser medium 3 is shared by the first resonator 11 and the second resonator 12.

[0078] In this way, by sharing the solid-state laser medium 3 between the first resonator 11 and the second resonator 12, the resonator length of the laser element 1f can be shortened, and laser light with a small pulse width and a large laser peak power can be emitted.

[0079] (Eighth embodiment) The laser device according to the eighth embodiment is configured such that a saturable absorber 4 is arranged closer to the light output surface than the solid-state laser medium 3 within the laser device 1f according to the seventh embodiment.

[0080] FIG. 13 is a schematic cross-sectional view of a laser device 1g according to an eighth embodiment. The laser device 1g of FIG. 13 has a configuration in which a solid-state laser medium 3 and a saturable absorber 4 are arranged in this order on the light-emitting surface side of a polarization separation element 10. The laser device 1g of FIG. 13 has a first reflective layer R1 to a fourth reflective layer R4. The first reflective layer R1 is arranged on the end face opposite to the light-emitting surface of the laminated semiconductor layer 2, which is the excitation light source 2. The second reflective layer R2 is arranged between the solid-state laser medium 3 and the saturable absorber 4. The third reflective layer R3 is arranged between the polarization separation element 10 and the laser device 1g. The fourth reflective layer R4 is arranged on the light-emitting surface side of the saturable absorber 4.

[0081] 13 has a first resonator 11 and a second resonator 12. The first resonator 11 resonates light of a first wavelength λ1 between the first reflective layer R1 and the second reflective layer R2. The second resonator 12 resonates light of a second wavelength λ2 between the third reflective layer R3 and the fourth reflective layer R4. The solid-state laser medium 3 is used in common as the first resonator 11 and the second resonator 12.

[0082] The laser element 1g of FIG. 13 can shorten the cavity length, and therefore can emit Q-switched pulsed laser light with a small pulse width, a large laser peak power, and no jitter, using excitation light that has been multiplexed by the polarization separation element 10 to improve the optical output.

[0083] Fig. 14 is a schematic cross-sectional view showing in more detail each layer of the laser device 1g of Fig. 13. The laminated semiconductor layer 2, which is the excitation light source 2, has two laminated semiconductor regions. Hereinafter, these two laminated semiconductor regions will be referred to as a first laminated semiconductor region 2a and a second laminated semiconductor region 2b.

[0084] The TM polarized light resonates between the first laminated semiconductor region 2a, the polarization separation element 10, and the solid-state laser medium 3. The TE polarized light emitted from the second laminated semiconductor region 2b and separated by the polarization separation element 10 is multiplexed with the TM polarized light inside the polarization separation element 10.

[0085] The pumping light source 2, which is made up of a laminated semiconductor layer 2 divided into a first laminated semiconductor region 2a and a second laminated semiconductor region 2b, has a structure in which a substrate 5, an n-contact layer 33, a fifth reflective layer R5, a cladding layer 6, an active layer 7, a cladding layer 8, a pre-oxidation layer 31, and a first reflective layer R1 are laminated in this order. Note that although the laser element 1g in Fig. 1 shows a bottom emission type configuration in which continuous wave (CW) pumping light is emitted from the substrate 5, it may also have a top emission type configuration in which CW pumping light is emitted from the first reflective layer R1 side.

[0086] The substrate 5 is, for example, an n-GaAs substrate 5. The n-GaAs substrate 5 is desirably as thin as possible because it absorbs a certain proportion of the light of the first wavelength λ1, which is the excitation wavelength of the excitation light source 2. On the other hand, it is desirably thick enough to maintain mechanical strength during the bonding process described below.

[0087] The active layer 7 emits light of the first wavelength λ1. The cladding layers 6 and 8 are, for example, AlGaAs cladding layers. The first reflective layer R1 reflects light of the first wavelength λ1. The fifth reflective layer R5 has a certain transmittance for light of the first wavelength λ1. The first reflective layer R1 and the fifth reflective layer R5 are, for example, electrically conductive semiconductor distributed Bragg reflectors (DBRs). Current is injected from the outside through the first reflective layer R1 and the fifth reflective layer R5, causing recombination and light emission in the quantum wells in the active layer 7, resulting in laser oscillation of the first wavelength λ1. A portion of the pre-oxidation layer (for example, an AlAs layer) 31 on the cladding layer side of the first reflective layer R1 is oxidized to become a post-oxidation layer (for example, an Al2O3 layer) 32.

[0088] The fifth reflective layer R5 is disposed on, for example, an n-GaAs substrate 5. For example, the fifth reflective layer R5 is made of Al doped with an n-type dopant (for example, silicon). z1 Ga 1-z1 As / Al z2 Ga 1-z2The fifth reflective layer R5 has a multilayer reflective film 17 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.

[0089] 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.

[0090] The first reflective layer R1 has a multi-reflection film made of, for example, Alz3Ga1-z3As / AlZ4Ga1-z4As (0≦z3≦z4≦1) doped with a p-type dopant (e.g., carbon). The first reflective layer R1 is also called a p-DBR.

[0091] The semiconductor layers R5, 6, 7, 8, and R1 in the excitation light source 2 can be formed using a crystal growth method such as MOCVD (metal organic chemical vapor deposition) or MBE (molecular beam epitaxy). After the crystal growth, processes such as mesa etching for element isolation, formation of an insulating film, and deposition of an electrode film are performed, enabling the device to be driven by current injection.

[0092] The solid-state laser medium 3 is bonded to the end face of the n-GaAs substrate 5 of the pumping light source 2 opposite to the fifth reflecting layer R5. Hereinafter, the end face of the solid-state laser medium 3 facing the pumping light source 2 will be referred to as the first face F1, and the end face of the solid-state laser medium 3 facing the saturable absorber 4 will be referred to as the second face F2. The laser pulse output face of the saturable absorber 4 will be referred to as the third face F3, and the end face of the pumping light source 2 facing the solid-state laser medium 3 will be referred to as the fourth face F4. The end face of the saturable absorber 4 facing the solid-state laser medium 3 will be referred to as the fifth face F5. Although shown separately in FIG. 1 for convenience, the fourth face F4 of the pumping light source 2 is bonded to the first face F1 of the solid-state laser medium 3, and the second face F2 of the solid-state laser medium 3 is bonded to the fifth face F5 of the saturable absorber 4.

[0093] 1 includes a first resonator 11 and a second resonator 12. The first resonator 11 resonates light of a first wavelength λ1 between a first reflective layer R1 in the pumping light source 2 and a second reflective layer R2 in the solid-state laser medium 3. The second resonator 12 resonates light of a second wavelength λ2 between a third reflective layer R3 in the solid-state laser medium 3 and a fourth reflective layer R4 in the saturable absorber 4.

[0094] The second resonator 12 is also called a Q-switched solid-state laser resonator 12. A second reflective layer R2, which is a highly reflective layer, is provided in the solid-state laser medium 3 so that the first resonator 11 can perform stable resonant operation. In a typical pumping light source 2, a partial reflecting mirror for emitting light of the first wavelength λ1 to the outside is disposed at the position of the second reflective layer R2 in FIG. 1. In contrast, in the laser device 1 in FIG. 1, the second reflective layer R2 is used to confine the power of the pumping light of the first wavelength λ1 within the first resonator 11, and therefore the second reflective layer R2 is made to be a highly reflective layer.

[0095] In this way, three reflective layers (the first reflective layer R1, the fifth reflective layer R5, and the second reflective layer R2) are provided inside the first resonator 11, which is composed of the pumping light source 2 and the solid-state laser medium 3. Therefore, the first resonator 11 has a coupled cavity structure.

[0096] 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 third reflective layer R3 in the solid-state laser medium 3 and the fourth reflective layer R4 in the saturable absorber 4. The third reflective layer R3 is a highly reflective layer, while the fourth reflective layer R4 is a partially reflective layer. In FIG. 1, the fourth reflective layer R4 is provided on the end face of the saturable absorber 4, but it may also be located behind the saturable absorber 4 along the optical axis. "Behind the optical axis" refers to the direction in which light is emitted on the optical axis. In other words, the fourth reflective layer R4 does not necessarily have to be located inside or on the surface of the saturable absorber 4. The fourth reflective layer R4 is an output coupling mirror in the second resonator 12.

[0097] 1, the pump light source 2, the solid-state laser medium 3, and the saturable absorber 4 are shown separately, but they are actually bonded together using a bonding process to form an integrated laminated structure. Examples of bonding processes that can be used include surface activated bonding, atomic diffusion bonding, and plasma activated bonding. Alternatively, other bonding (adhesion) processes can be used.

[0098] To stably bond the solid-state laser medium 3 to the pumping light source 2, the surface of the n-GaAs substrate 5 within the pumping light source 2 must be flat. Therefore, as described above, it is desirable to arrange the electrodes E1 and E2, which are used to inject current into the first reflective layer R1 and the fifth reflective layer R5, so that they are not exposed on the surface of the n-GaAs substrate 5. In the example shown in FIG. 1 , electrodes E1 and E2 are arranged on the end face of the pumping light source 2 facing the first reflective layer R1. Electrode E1 is a p-electrode and is electrically connected to the first reflective layer R1. Electrode E2 is an n-electrode formed by filling the inner wall of a trench extending from the first reflective layer R1 to the n-contact layer 33 with a conductive material 35 via an insulating film 34. Arranging electrodes E1 and E2 on the same end face of the pumping light source 2 as shown in FIG. 1 allows this end face to be solder-mounted to a support substrate (not shown). Even when multiple laser elements 1 are arranged in an array, arranging electrodes E1 and E2 on the same end face allows this end face to be mounted to a support substrate. The shapes and locations of the electrodes E1 and E2 shown in FIG. 1 are merely examples.

[0099] 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.

[0100] 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 the layers and bonded via the dielectric multilayer film. For example, the refractive index n of the GaAs substrate 5, which serves as the base substrate for the pumping light source 2, at a wavelength of 940 nm is 3.5, which is higher than that of YAG (n: 1.8) and other common dielectric multilayer film materials. Therefore, when bonding the solid-state laser medium 3 and saturable absorber 4 to the pumping light source 2, it is necessary to prevent optical loss due to refractive index mismatch. Specifically, it is desirable to place an anti-reflection film (AR coating or anti-reflection coating) between the pumping light source 2 and the solid-state laser medium 3 to prevent reflection of the light of the first wavelength λ1 of the first resonator 11. It is also desirable to place an anti-reflection film (AR coating film or anti-reflection coating film) between the solid-state laser medium 3 and the saturable absorber 4 .

[0101] 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.

[0102] Dielectric multilayer films include short-wavelength transmission filter films (SWPF), long-wavelength transmission filter films (LWPF), band-pass filter films (BPF), and anti-reflection protective films (AR). These films are coating layers consisting of alternating layers of high-refractive index material and low-refractive index material. It is desirable to use different types of dielectric multilayer films as needed. The dielectric multilayer film can be formed by physical vapor deposition (PVD), specifically, vacuum deposition, ion-assisted deposition, sputtering, or other deposition methods. The film formation method is not critical. The properties of the dielectric multilayer film can also be selected arbitrarily. For example, the third reflective layer R3 can be a short-wavelength transmission filter film, and the second reflective layer R2 can be a long-wavelength transmission filter film. Applying a long-wavelength transmission filter film to the second reflective layer R2 can prevent the first wavelength λ1 from penetrating the saturable absorber 4, thereby preventing malfunction of the Q switch. Note that short wavelength transmission means transmitting light of the first wavelength λ1 and reflecting light of the second wavelength λ2, while long wavelength transmission means reflecting light of the first wavelength λ1 and transmitting light of the second wavelength λ2.

[0103] Furthermore, a diffraction grating may be provided inside the second resonator 12 to convert the polarization state of the emitted laser pulse from random polarization to linear polarization. The photonic crystal structure or the fine grooves of the diffraction grating can be used as an interface for bonding by forming a film of a material such as SiO2 and polishing it.

[0104] 14, when a current is injected into the active layer 7 via the electrodes of the pumping light source 2, laser oscillation of the first wavelength λ1 occurs in the first resonator 11, and the solid-state laser medium 3 is excited. Because the saturable absorber 4 is bonded to the solid-state laser medium 3, in the initial stage when laser oscillation of the first wavelength λ1 occurs, 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.

[0105] 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 ).

[0106] As described above, in the laser device 1g according to the eighth embodiment, TM polarized light is combined with TE polarized light inside the polarization separation element 10 and then output as light, thereby increasing the optical output power emitted from the polarization separation element 10. The first resonator 11 resonates light of the first wavelength λ1 between the first reflective layer R1 disposed on the end faces opposite to the light-emitting surfaces of the first laminated semiconductor region 2a and the second laminated semiconductor region 2b, and the second reflective layer R2 disposed between the solid-state laser medium 3 and the saturable absorber 4. The second resonator 12 resonates light of the second wavelength λ2 between the third reflective layer R3 disposed between the polarization separation element 10 and the solid-state laser medium 3, and the fourth reflective layer R4 disposed on the light-emitting surface side of the saturable absorber 4. By sharing the solid-state laser medium 3 between the first resonator 11 and the second resonator 12, it is possible to emit Q-switched pulsed laser light that has a small pulse width, a large laser peak power, and is free of jitter.

[0107] (Ninth embodiment) The laser elements 1 to 1g according to the first to eighth embodiments can be arranged in an array. Figure 15 shows a plan view and a cross-sectional view of a plurality of laser elements 1h arranged in an array.

[0108] As shown in the figure, the laminated semiconductor layer 2 constituting the pumping light source 2 is divided into multiple laminated semiconductor regions 2a and 2b. One of the two adjacent laminated semiconductor regions 2a and 2b is used to emit TM polarized light, and the other is used to combine TE polarized light with TM polarized light. Therefore, of the two light emitting portions corresponding to the two adjacent laminated semiconductor regions 2a and 2b, one Mesa A emits pumping light, while the other Mesa B emits almost no pumping light. Therefore, the light emitting portion from which the pumping light is emitted may be made larger.

[0109] In this way, in the ninth embodiment, a plurality of laser elements 1h each having an increased optical output power due to the provision of the polarization separation element 10 are arranged in a two-dimensional direction, thereby realizing a laser element 1h capable of high optical output power and long life.

[0110] (Tenth embodiment) It is also possible to fabricate a laser amplifier using the structure of the laser device 1d or 1f shown in FIG. 10 or FIG.

[0111] Fig. 16A is a cross-sectional view of the laser amplification element 50 according to the present disclosure, Fig. 16B is a perspective view of the laser amplification element 50 according to the present disclosure, and Fig. 16C is a plan view schematically showing the optical path of the laser light within the laser amplification element 50.

[0112] 16A to 16C includes a pumping light source 53 disposed on a support substrate 51 via a submount substrate 52, a polarization separation element 60 disposed on the pumping light source 53, and a solid-state laser medium 54 disposed on the polarization separation element 60, and does not include a saturable absorber 4. The solid-state laser medium 54 is, for example, Yb:YAG. As will be described later, the pumping light source 53 and the solid-state laser medium 54 form a first resonator 55, and light of a first wavelength λ1 is resonated in the vertical direction (stacking direction) of FIG. 16A. More specifically, the first resonator 55 resonates light of the first wavelength λ1 between a first reflective layer R1 (p-DBR 72) in the pumping light source 53 and a second reflective layer R2 in the solid-state laser medium 54. The solid-state laser medium 3 in the laser element 1 in FIG. 1 has a third reflecting layer R3 on the end face facing the excitation light source 2 and a fourth reflecting layer R4 on the end face facing the saturable absorber 4, but the solid-state laser medium 54 in FIG. 16A does not need a reflecting layer on the end face facing the excitation light source 53, and has a second reflecting layer R2 on the end face opposite to that.

[0113] 16A to 16C includes a first reflecting member 56 and a second reflecting member 57 arranged along the opposing first side surface 54S1 and second side surface 54S2 of the solid-state laser medium 54, and the solid-state laser medium 54 functioning as an amplifying medium 83 that causes light of the second wavelength λ2 to travel back and forth multiple times between the first reflecting member 56 and the second reflecting member 57.

[0114] The first reflecting member 56 and the second reflecting member 57 may have flat reflecting mirrors, or may have convex reflecting mirrors to avoid optical damage to the material due to the increased light density during the amplification process.

[0115] In FIG. 16A, the first reflecting member 56 and the second reflecting member 57 are arranged at a distance from the first side surface 54S1 and the second side surface 54S2 of the solid-state laser medium 54, but a multilayer film formed by stacking at least one of a semiconductor material, a metal material, and a dielectric material on the first side surface 54S1 and the second side surface 54S2 may be used as a reflecting mirror.

[0116] 16A to 16C further includes an optical input portion IN provided along the first side surface 54S1 and an optical output portion OUT provided along the second side surface 54S2. The optical input portion IN inputs weak light (seed light) having a second wavelength λ2 to the first side surface 54S1. The light having the second wavelength λ2 travels back and forth through the amplifying medium 83 multiple times and is emitted from the optical output portion OUT.

[0117] Furthermore, the laser amplifier 50 according to this embodiment has a polarization separation element 60 similar to the polarization separation element 10 according to the first to ninth embodiments. By providing the polarization separation element 60, the optical output emitted from the polarization separation element 10 can be increased.

[0118] 16A to 16C may also include a cooling member 62. The cooling member 62 is bonded to the side surfaces of the pumping light source 53, the polarization separation element 60, and the solid-state laser medium 54, and dissipates heat generated by at least one of the pumping light source 53, the polarization separation element 60, and the solid-state laser medium 54. The cooling member 62 is made of a metal material with high thermal conductivity, such as Cu. The cooling member 62 may be bonded to a package (not shown), or heat may be dissipated from the cooling member 62 to the package.

[0119] 16A to 16C, the support substrate 51 is, for example, a Cu substrate, and a submount substrate 52 is disposed thereon. The submount substrate 52 has, for example, a laminated structure of a SiC layer 64 and an AuSn layer 65, and a p-electrode 73 and an n-electrode 74 of the excitation light source 53 are bonded onto the AuSn layer 65 while being electrically insulated from each other.

[0120] The excitation light source 53 is a laminated semiconductor layer 2 in which an n-contact layer 67, an n-DBR 68, a cladding layer 69, an active layer 70, a cladding layer 71, and a p-DBR 72 are laminated in this order on an n-GaAs substrate 66. P-electrodes 73 and n-electrodes 74 are alternately disposed on the p-DBR 72. The p-electrode 73 is electrically connected to the p-DBR 72, and the n-electrode 74 is electrically connected to the n-DBR 68 through a via 75.

[0121] The laser amplifier device 50 according to the present disclosure includes a first resonator 55, similar to that shown in FIG. 1. The first resonator 55 resonates light of a first wavelength λ1 between a first reflective layer R1 in the pumping light source 53 and a second reflective layer R2 in the solid-state laser medium 54. The first reflective layer R1 is a p-DBR 72, and the second reflective layer R2 is disposed on the upper surface of a heat dissipation member 61, for example. The heat dissipation member 61 may be omitted. The solid-state laser medium 54 is excited by the resonant action of the light of the first wavelength λ1 in the first resonator 55. In FIG. 16A, the resonant action of the first resonator 55 is schematically indicated by a thin line. Amplified light (seed light) of a second wavelength λ2 is incident on the excited solid-state laser medium 54 from the right end of FIG. 16A to the left. This causes stimulated emission of the amplified light, and the amplified light is laser-amplified.

[0122] Furthermore, when Yb:YAG is used as the amplifying medium 83, if laser light with a wavelength of 1030 nm is used as the seed light, the seed light will be absorbed in the unexcited region of the amplifying medium 83, resulting in a problem of insufficient amplification. For this reason, when Yb:YAG is used as the amplifying medium 83, seed light with a wavelength of 1050 nm, which does not cause optical absorption even in the unexcited state, can be used. In this case, the wavelength of the seed light is not limited to 1050 nm, as long as it does not cause optical absorption even in the unexcited state.

[0123] In this way, by providing the solid-state laser medium 54 inside the first resonator 55, the optical configuration can be greatly simplified and miniaturized.

[0124] Furthermore, the size of the solid-state laser medium 54 in the laser amplifying element 50 according to the present disclosure is not limited by the absorption length of the pumping light, and therefore the area of ​​the solid-state laser medium 54 can be increased regardless of the absorption length of the pumping light. By increasing the area of ​​the solid-state laser medium 54, the amplification factor of the laser amplifying element 50 can be further improved.

[0125] Furthermore, the laser amplification element 50 according to the present disclosure can integrally bond the excitation light source 53 made of the laminated semiconductor layer 2 and the solid-state laser medium 54, and can be manufactured using a general-purpose semiconductor process, which makes it easy to miniaturize the element and reduces manufacturing costs.

[0126] <<Application Example>> The technology disclosed herein can be widely applied to medical imaging systems (hereinafter also referred to as electronic devices), ranging systems such as LiDAR (Light Detection and Ranging) devices, light sources for laser processing devices, etc. Medical imaging systems are medical systems that use imaging technology, such as endoscope systems and microscope systems.

[0127] [Endoscope system] An example of an endoscopic system will be described with reference to FIGS. 17 and 18. FIG. 17 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. 18 is a diagram illustrating an example of the configuration of an endoscope 5001 and a CCU (Camera Control Unit) 5039. FIG. 17 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. 17, 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.

[0128] 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.

[0129] 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.

[0130] [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. 18 , 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.

[0131] [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. 18 . 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.

[0132] 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).

[0133] [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.

[0134] [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.

[0135] [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.

[0136] [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.

[0137] [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.

[0138] 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.

[0139] [Microscope system] 19 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.

[0140] 19 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 a 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.

[0141] 19, during surgery, a microsurgical system 5300 is used, and an image of the surgical site captured by a microscope device 5301 is enlarged and displayed on a display device 5041 installed in an operating room. The display device 5041 is installed in a position facing an operator 5067, who performs various procedures on the surgical site, such as resecting the affected area, while observing the state of the surgical site using the image displayed on the display device 5041. Microsurgical systems are used, for example, in ophthalmic surgery and brain surgery.

[0142] 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.

[0143] 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.

[0144] The present technology can be configured as follows: (1) a laminated semiconductor layer having a first reflective layer for light of a first wavelength and an active layer for surface emitting light of the first wavelength; a second reflective layer for light of the first wavelength, the second reflective layer being disposed closer to the light emitting surface than the laminated semiconductor layer; a polarization separation element that individually resonates each of the orthogonal polarized light beams included in the light emitted from the laminated semiconductor layer between the first reflective layer and the second reflective layer to combine them. (2) The laser element described in (1), wherein the laminated semiconductor layer has a plurality of laminated semiconductor regions corresponding to the orthogonal polarized light, and the polarization separation element individually resonates the corresponding polarized light between the first reflecting layer and the second reflecting layer for each of the plurality of laminated semiconductor regions, thereby combining the corresponding polarized light. (3) A laser element described in (1) or (2), wherein the polarization separation element has a first surface that is in contact with the light emitting surface of the laminated semiconductor layer, and a second surface that is disposed between the first reflective layer and the second reflective layer on the opposite side of the first surface. (4) A laser element described in any one of (1) to (3), wherein the orthogonal polarized light beams include orthogonal polarized light beams of different wavelengths, and the polarization separation element individually resonates each of the orthogonal polarized light beams including the orthogonal polarized light beams of different wavelengths between the first reflective layer and the second reflective layer to combine them. (5) The orthogonally polarized light includes TM (Transverse Magnetic) polarized light and TE (Transverse Electric) polarized light, The laser element according to (4), wherein the polarization separation element resonates the TE polarized light and the TM polarized light individually between the first reflecting layer and the second reflecting layer to combine them. (6) The laser element according to (5), wherein the polarization separation element multiplexes the TE polarized light with the TM polarized light inside the polarization separation element. (7) The polarization separation element has a laminate in which a plurality of polarization separation films and a plurality of reflective films are alternately stacked at intervals, the laminate has a cut surface cut at an angle of 45 degrees to the normal direction of the laminate surface, The laser element according to any one of (1) to (6), wherein the polarization separation element is arranged so that a normal direction of the cut surface is parallel to a normal direction of the laminated semiconductor layer. (8) The laser element according to any one of (1) to (6), wherein the polarization separation element includes a birefringent material that separates the light emitted from the stacked semiconductor layer into the orthogonally polarized light. (9) A laser element according to any one of (1) to (8), comprising a laser medium arranged closer to the light emitting surface than the polarization separation element and resonating at a second wavelength different from the first wavelength. (10) a third reflective layer for light of the second wavelength, the third reflective layer being disposed on a first end surface of the laser medium on the polarization separation element side; The laser element according to (9), further comprising: a fourth reflective layer for light of the second wavelength, the fourth reflective layer being disposed on a second end face of the laser medium opposite to the first end face. (11) The laser element according to (10), wherein the third reflective layer is disposed closer to the light emitting surface than the second reflective layer. (12) The laser element according to (10), wherein the third reflective layer is disposed between the polarization separation element and the second reflective layer. (13) The laser element according to (12), wherein the third reflective layer is in contact with an end face of the polarization separation element. (14) The laser element according to any one of (10) to (13), wherein the fourth reflective layer is in contact with the second reflective layer or is disposed closer to the light emitting surface than the second reflective layer. (15) The laser element according to (9), further comprising a saturable absorber disposed closer to the light emitting surface than the laser medium. (16) A third reflective layer for the light of the second wavelength, which is disposed on an end surface of the laser medium facing the polarization separation element; The laser element according to (15), further comprising: a fourth reflective layer for light of the second wavelength, the fourth reflective layer being disposed on the light emission surface side of the saturable absorber. (17) The laser element according to (16), wherein the third reflective layer is disposed closer to the light emitting surface than the second reflective layer. (18) The laser element according to (16), wherein the second reflective layer is disposed between the third reflective layer and the fourth reflective layer. (19) A laser element described in any one of (15) to (18), wherein each of the laminated semiconductor layer, the polarization separation element, the laser medium, and the saturable absorber is divided into a plurality of regions corresponding to a plurality of light-emitting units that emit pulsed laser light of the second wavelength and are arranged at predetermined intervals. (20) A laser element; a control unit that controls the emission of light from the laser element, The laser element is a laminated semiconductor layer having a first reflective layer for light of a first wavelength and an active layer for surface emitting light of the first wavelength; a second reflective layer for light of the first wavelength, the second reflective layer being disposed closer to the light emitting surface than the laminated semiconductor layer; and a polarization separation element that individually resonates each of a plurality of polarized light beams included in the light emitted from the laminated semiconductor layer between the first reflective layer and the second reflective layer to combine the light beams.

[0145] The aspects of the present disclosure are not limited to the individual embodiments described above, but include various modifications that may be conceived by those skilled in the art, and the effects of the present disclosure are not limited to the above-described contents. In other words, various additions, modifications, and partial deletions are possible within the scope of the conceptual idea and spirit of the present disclosure, which is derived from the contents defined in the claims and their equivalents. [Explanation of symbols]

[0146] 1, 1a, 1b, 1c, 1d, 1e, 1f, 1g, 1h laser element, 2 pumping light source (laminated semiconductor layer), 2a first laminated semiconductor region, 2b second laminated semiconductor region, 3 solid-state laser medium, 4 saturable absorber, 5 n-GaAs substrate, 6 cladding layer, 7 active layer, 8 cladding layer, 10 polarization separation element, 11 first resonator, 12 second resonator, 13 first optical member, 14 second optical member, 15 material layer, 16 polarization separation film, 17 reflective film, 17a first reflective film, 17b second reflective film, 20 light emitting portion, 21 base layer, 22 first substrate, 23 base layer, 24 second substrate, 25 laminate, 31 pre-oxidation layer, 32 post-oxidation layer (e.g., Al2O3 layer), 33 contact layer, 34 insulating film, 35 conductive material, 50 Laser amplifier element, 51 support substrate, 52 submount substrate, 53 pumping light source, 54 solid-state laser medium, 55 first resonator, 56 first reflecting member, 57 second reflecting member, 60 polarization splitter element, 61 heat dissipation member, 62 cooling member, 64 SiC layer, 65 AuSn layer, 66 n-GaAs substrate, 67 contact layer, 69 cladding layer, 70 active layer, 71 cladding layer, 73 p-electrode, 74 n-electrode, 75 via, 83 amplification medium, 100 laser element

Claims

1. a laminated semiconductor layer having a first reflective layer for light of a first wavelength and an active layer for surface emitting light of the first wavelength; a second reflective layer for light of the first wavelength, the second reflective layer being disposed closer to the light emitting surface than the laminated semiconductor layer; a polarization separation element that individually resonates each of the orthogonal polarized light beams included in the light emitted from the laminated semiconductor layer between the first reflective layer and the second reflective layer to combine them.

2. the laminated semiconductor layer has a plurality of laminated semiconductor regions corresponding to the orthogonally polarized light, 2. The laser element according to claim 1, wherein the polarization separation element individually resonates corresponding polarized light between the first reflective layer and the second reflective layer for each of the plurality of stacked semiconductor regions, and combines the corresponding polarized light.

3. 2. The laser element according to claim 1, wherein the polarization separation element has a first surface that is in contact with the light emitting surface of the laminated semiconductor layer, and a second surface that is disposed between the first reflective layer and the second reflective layer on the opposite side of the first surface.

4. the orthogonally polarized light includes orthogonally polarized light of different wavelengths, 2. The laser element according to claim 1, wherein the polarization separation element individually resonates each of the orthogonally polarized light beams, including orthogonally polarized light beams of different wavelengths, between the first reflective layer and the second reflective layer to combine them.

5. the orthogonally polarized light includes TM (Transverse Magnetic) polarized light and TE (Transverse Electric) polarized light, 5. The laser element according to claim 4, wherein the polarization separation element causes the TE polarized light and the TM polarized light to resonate individually between the first reflecting layer and the second reflecting layer, and combines the light.

6. The laser device according to claim 5 , wherein the polarization separation element multiplexes the TE polarized light with the TM polarized light inside the polarization separation element.

7. the polarization separation element has a laminate in which a plurality of polarization separation films and a plurality of reflective films are alternately stacked at intervals, the laminate has a cut surface cut at an angle of 45 degrees to the normal direction of the laminate surface, The laser element according to claim 1 , wherein the polarization separation element is disposed so that a normal direction to the cut surface is parallel to a normal direction to the laminated semiconductor layers.

8. 2. The laser device according to claim 1, wherein the polarization separation element includes a birefringent material that separates the light emitted from the laminated semiconductor layer into the orthogonally polarized light beams.

9. 2. The laser element according to claim 1, further comprising: a laser medium that is disposed closer to the light exit surface than the polarization separation element and that resonates at a second wavelength different from the first wavelength.

10. a third reflective layer for light of the second wavelength, the third reflective layer being disposed on a first end surface of the laser medium on the polarization separation element side; 10. The laser device according to claim 9, further comprising: a fourth reflective layer for light of the second wavelength, the fourth reflective layer being disposed on a second end face of the laser medium opposite to the first end face.

11. The laser element according to claim 10 , wherein the third reflective layer is disposed closer to the light emitting surface than the second reflective layer.

12. The laser device according to claim 10 , wherein the third reflective layer is disposed between the polarization separation element and the second reflective layer.

13. The laser device according to claim 12 , wherein the third reflective layer is in contact with an end face of the polarization separation element.

14. The laser element according to claim 10 , wherein the fourth reflective layer is in contact with the second reflective layer or is disposed closer to the light emitting surface than the second reflective layer.

15. 10. The laser device according to claim 9, further comprising a saturable absorber disposed closer to the light emitting surface than the laser medium.

16. a third reflective layer for the light of the second wavelength, the third reflective layer being disposed on an end surface of the laser medium facing the polarization separation element; 16. The laser device according to claim 15, further comprising: a fourth reflective layer for light of the second wavelength, the fourth reflective layer being disposed on a light emission surface side of the saturable absorber.

17. The laser element according to claim 16 , wherein the third reflective layer is disposed closer to the light emitting surface than the second reflective layer.

18. The laser device of claim 16 , wherein the second reflective layer is disposed between the third reflective layer and the fourth reflective layer.

19. 16. The laser element according to claim 15, wherein each of the laminated semiconductor layer, the polarization separation element, the laser medium, and the saturable absorber is divided into a plurality of regions corresponding to a plurality of light emitting units that emit pulsed laser light of the second wavelength and are arranged at predetermined intervals.

20. a laser element; a control unit that controls the emission of light from the laser element, The laser element is a laminated semiconductor layer having a first reflective layer for light of a first wavelength and an active layer for surface emitting light of the first wavelength; a second reflective layer for light of the first wavelength, the second reflective layer being disposed closer to the light emitting surface than the laminated semiconductor layer; and a polarization separation element that individually resonates each of the orthogonal polarized light beams included in the light emitted from the laminated semiconductor layer between the first reflective layer and the second reflective layer to combine them.

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