Semiconductor laser element and wavelength beam coupling device

Abstract

Provided are a semiconductor laser element and a wavelength beam coupling device capable of reducing the spectral line width of laser light. A semiconductor laser element according to the present disclosure comprises: a semiconductor laminate part including a substrate, an n-side semiconductor layer part, an active layer, and a p-side semiconductor layer part; and a positive electrode in contact with the p-side semiconductor layer part. The semiconductor laminate part includes a first portion that includes a first cladding region, a first core region, and a second cladding region and that allows laser light to propagate in a plurality of transverse modes, and a second portion that includes a diffraction grating. The positive electrode is in contact with the p-side semiconductor layer part in at least the first portion. The laser light emitted from the first portion propagates through the second portion at a maximum diffusion angle θmax. In a top plan view, both ends, in a direction perpendicular to the optical axis of the laser light, of the second portion are positioned outside imaginary lines each extending from the boundary between the first portion and the second portion at the maximum diffusion angle θmax.

Description

Semiconductor laser element and wavelength beam combining device

[0001] The present disclosure relates to semiconductor laser devices and wavelength beam combining devices.

[0002] In recent years, there has been a demand for semiconductor laser elements with higher laser beam output. High-output semiconductor laser elements can be used, for example, as light sources for processing. Transverse multimode semiconductor laser elements tend to produce higher output than transverse single-mode semiconductor laser elements. Therefore, transverse multimode semiconductor laser elements are used as high-output semiconductor laser elements. For example, Patent Document 1 discloses a transverse multimode semiconductor laser element.

[0003] JP 2011-151238 A

[0004] However, the transverse multimode semiconductor laser device disclosed in Patent Document 1 uses a multimode waveguide, and since the equivalent refractive index differs for each transverse mode, the oscillation wavelength differs for each transverse mode, resulting in a broad spectral linewidth of the emitted laser light.

[0005] An object of an embodiment of the present disclosure is to provide a semiconductor laser element and a wavelength beam combining device that can narrow the spectral linewidth of laser light.

[0006] A first embodiment comprises: a substrate; a semiconductor laminate having an n-side semiconductor layer, a p-side semiconductor layer, and an active layer disposed between the n-side semiconductor layer and the p-side semiconductor layer; and a positive electrode in contact with the p-side semiconductor layer, wherein the semiconductor laminate comprises: a first portion having a first cladding region, a second cladding region, and a first core region located between the first cladding region and the second cladding region, and propagating laser light in a plurality of transverse modes; and a second portion including a diffraction grating, wherein the positive electrode is in contact with the p-side semiconductor layer at least in the first portion, the diffraction grating is provided in the p-side semiconductor layer, and includes a periodic structure of the p-side semiconductor layer and a first medium made of a material different from that of the p-side semiconductor layer, and an upper end of the p-side semiconductor layer forming the diffraction grating is in contact with a bottom surface of a second medium, The laser light emitted from the first portion has a maximum divergence angle Θ determined by the refractive index of the first core region, the refractive index of the first cladding region, the refractive index of the second cladding region, and the refractive index of the second portion. max When viewed from above, both ends of the second portion in a direction perpendicular to the optical axis of the laser light are spaced apart from the boundary between the first portion and the second portion by the maximum divergence angle Θ max The semiconductor laser element is located outside the imaginary line extending as shown in FIG.

[0007] The second embodiment comprises: a substrate; a semiconductor laminate having an n-side semiconductor layer, a p-side semiconductor layer, and an active layer disposed between the n-side semiconductor layer and the p-side semiconductor layer; and a positive electrode in contact with the p-side semiconductor layer, wherein the semiconductor laminate comprises: a first portion having a first cladding region, a second cladding region, and a first core region located between the first cladding region and the second cladding region, and propagating laser light in a plurality of transverse modes; and a second portion including a diffraction grating, wherein the positive electrode is in contact with the p-side semiconductor layer at least in the first portion, the diffraction grating is provided in the p-side semiconductor layer and includes a periodic structure of the p-side semiconductor layer and a first medium made of a material different from the p-side semiconductor layer, an upper end of the p-side semiconductor layer forming the diffraction grating is in contact with a bottom surface of a second medium, and the second portion has a first end face for emitting laser light, In a top view, the width of the first end face in a direction perpendicular to the direction of the period of the diffraction grating is larger than the beam diameter of the laser light at the first end face, and in a direction perpendicular to the direction of the period of the diffraction grating, in a top view, the second portion is also located in a direction away from the central axis of the laser light, based on the shorter of the lines connecting an edge that defines the beam diameter of the laser light at the first end face and one of both ends of the boundary between the first core region and the second portion.

[0008] A third embodiment is a semiconductor laser element comprising: a substrate; a semiconductor laminate having an n-side semiconductor layer portion, a p-side semiconductor layer portion, and an active layer disposed between the n-side semiconductor layer portion and the p-side semiconductor layer portion; and a positive electrode in contact with the p-side semiconductor layer portion, wherein the semiconductor laminate portion comprises a first portion which is a channel waveguide and a second portion which is a slab waveguide, the first portion is a multi-mode waveguide, and the second portion includes a diffraction grating, the positive electrode is in contact with at least the p-side semiconductor layer portion in the first portion, the diffraction grating is provided in the p-side semiconductor layer portion, and includes a periodic structure of the p-side semiconductor layer portion and a first medium made of a material different from that of the p-side semiconductor layer portion, and an upper end of the p-side semiconductor layer portion forming the diffraction grating is in contact with a bottom surface of the second medium.

[0009] The fourth embodiment is a wavelength beam combining device that includes a plurality of light source units and a combining optical element, each of the plurality of light source units having any of the semiconductor laser elements described above and a collimating lens provided at a position where the laser light emitted from the semiconductor laser element is incident, the peak wavelength of the laser light differs for each of the plurality of light source units, and the optical element combines the laser light emitted from the plurality of light source units.

[0010] According to one aspect of the present disclosure, it is possible to provide a semiconductor laser element and a wavelength beam combining device that can narrow the spectral linewidth of laser light.

[0011] 3A is a top view showing an overview of the semiconductor laser element of embodiment 1. FIG. 4 is a top view showing the semiconductor laser element of embodiment 1 including a non-wavelength selective region. FIG. 5 is a top view showing the semiconductor laser element of embodiment 1. FIG. 6 is a cross-sectional view taken along line IIIA-IIIA in FIG. 2. FIG. 7 is a partially enlarged view of the vicinity of the diffraction grating in FIG. 3A. FIG. 8 is a cross-sectional view taken along line IV-IV in FIG. 2. FIG. 9 is a cross-sectional view taken along line V-V in FIG. 2. ２ 14A ; 14B ; 14C ; 14D ; 14E ; 14F ; 14G ; 14H ; 14H ; 14I ...

[0012] In this specification, the term "process" does not only refer to an independent process, but also includes processes that cannot be clearly distinguished from other processes as long as the purpose of the process is achieved. Hereinafter, embodiments of the present invention will be described in detail. However, the embodiments shown below are intended to exemplify semiconductor laser elements, manufacturing methods thereof, and wavelength beam combiners for embodying the technical concept of the present invention, and the present invention is not limited to the semiconductor laser elements, manufacturing methods thereof, and wavelength beam combiners shown below.

[0013] <Embodiment 1> A semiconductor laser device of embodiment 1 will be described with reference to Figures 1A to 5. In this specification, directions are defined as follows: "Height direction" means the stacking direction of the semiconductor stack 30. In the drawings, this is represented by the Z axis. The length in this direction is simply called "height" or "thickness". "Periodic direction" means the direction forming the period of the diffraction grating 20. In the drawings, this is represented by the X axis. "Width direction" means the direction perpendicular to both the height direction and the periodic direction. In the drawings, this is represented by the Y axis. The length in this direction is simply called "width".

[0014] (Semiconductor laser element L1) The semiconductor laser element L1 according to one embodiment of the present disclosure includes a substrate, a semiconductor laminate including an n-side semiconductor layer portion, a p-side semiconductor layer portion, and an active layer disposed between the n-side semiconductor layer portion and the p-side semiconductor layer portion, and a positive electrode in contact with the p-side semiconductor layer portion. The semiconductor laminate includes a first portion having a first cladding region, a second cladding region, and a first core region located between the first cladding region and the second cladding region, and propagating laser light in multiple transverse modes, and a second portion including a diffraction grating. The positive electrode is in contact with at least the first portion of the p-side semiconductor layer portion. The diffraction grating is provided in the p-side semiconductor layer portion and includes a periodic structure of the p-side semiconductor layer portion and a first medium made of a material different from the p-side semiconductor layer portion, and an upper end of the p-side semiconductor layer portion forming the diffraction grating is in contact with a bottom surface of the second medium. The laser light emitted from the first portion has a maximum divergence angle Θ determined by the refractive index of the first core region, the refractive index of the first cladding region, the refractive index of the second cladding region, and the refractive index of the second portion. maxIn top view, both ends of the second portion in the direction perpendicular to the optical axis of the laser light are separated from the boundary between the first portion and the second portion by a maximum divergence angle Θ max It is located outside the imaginary line that extends from

[0015] The diffraction grating extending beyond the spread of the laser light makes it possible to obtain a semiconductor laser element L1 capable of narrowing the spectral line width of the laser light.

[0016] First, an overview of the semiconductor laser device L1 will be described using FIGS. 1A and 3A. FIG. 1A is a top view showing an outline of the semiconductor laser device L1. For simplicity, the positive electrode 41, the negative electrode 42, the insulating layer 70, and the like are omitted from FIG. 1A. Diagrams including the positive electrode 41, the negative electrode 42, and the insulating layer 70 are shown in FIGS. 2 to 5. FIG. 3A is a cross-sectional view of the semiconductor laser device L1 taken along line IIIA-IIIA in FIG. 2. The semiconductor laser device L1 includes a substrate 300 and a semiconductor laminate 30 provided on the substrate 300. The semiconductor laminate 30 includes a first portion 1 and a second portion 2. The first portion 1 is a region including an optical waveguide capable of guiding multiple transverse modes. The second portion 2 is a region into which light generated in the first portion 1 is incident and includes a diffraction grating 20. The diffraction grating 20 feeds back, to the first portion 1, light having a wavelength corresponding to the Bragg wavelength, from the light incident from the first portion 1. 1A , a high-reflection film 62 is provided on the end face closer to the first portion 1, and resonance occurs between the diffraction grating 20 and the high-reflection film 62. The generated laser light is emitted, for example, from the end face closer to the second portion 2. The semiconductor laser element L1 of the present disclosure is a semiconductor laser element that oscillates in multiple transverse modes, but is able to narrow the spectral linewidth of the laser light due to the wavelength selectivity of the diffraction grating 20.

[0017] FIG. 2 is a top view of the semiconductor laser device L1. The dashed line in FIG. 2 indicates the ridge 135. As shown in FIGS. 4 and 5 (described later), the ridge 135 has a first ridge 135a provided in the first portion 1 and a second ridge 135b provided in the second portion. As shown in FIGS. 4 and 5 (details), the side surfaces of the first ridge 135a and the second ridge 135b are inclined in the height direction. The dashed lines in FIG. 2 indicate the lower and upper ends of the inclined side surfaces of these ridges. An anti-reflection film 63 may be provided on the end surface closer to the second portion 2, as shown in FIG. 2 (details). The boundary point P1 shown in FIG. 2 corresponds to the boundary point P1 in FIG. 1A (or FIG. 1B). The boundary point P1 will be described later.

[0018] Next, a brief description will be given of the operation of the semiconductor laser element L1 during operation. The semiconductor laser element L1 has a first portion 1, which is a multimode waveguide, and a second portion 2, which includes a diffraction grating 20. A plurality of transverse modes are guided in the first portion 1 and enter the second portion 2. The light entering the second portion 2 has a maximum divergence angle Θ, which is determined by the refractive index of the first core region 13 of the first portion 1, the refractive index of the first cladding region 11 of the first portion 1, the refractive index of the second cladding region 12 of the first portion 1, and the refractive index of the second portion 2. max The maximum divergence angle Θ max is an angle also called the maximum light-receiving angle. The two widthwise ends of the second portion 2 are spaced apart from the boundary between the first portion 1 and the second portion 2, indicated by point P1 in FIG. 1A, by a maximum diffusion angle Θ max It is located outside the imaginary line that extends from

[0019] The width of the region where the diffraction grating 20 is provided is larger than the spread of light indicated by the imaginary line. As a result, the wavelength selection by the diffraction grating 20 takes substantially the same value regardless of the transverse mode. More specifically, the oscillation wavelength λ is determined by the period Λ of the diffraction grating 20 and the refractive index n of the second portion 2. ２ Using the above, it is expressed by the following equation (1): λ=2×Λ×n ２ (1)

[0020] The width of the second portion 2 is the maximum diffusion angle Θ max Since it extends beyond the virtual line that spreads at ２ is substantially independent of the transverse mode.２ is the equivalent refractive index. ２ Since takes the same value in any transverse mode, the oscillation wavelength is the same.

[0021] On the other hand, when a diffraction grating is provided in the optical waveguide of a semiconductor laser element including a multimode waveguide, as in a conventional distributed feedback laser element or distributed Bragg reflector laser element, the oscillation wavelength differs for each transverse mode. This is because the larger the mode order of the transverse mode guided through the optical waveguide, the more it leaks into the cladding, and the equivalent refractive index differs for each transverse mode. That is, in the following formula (2), the refractive index N of the mth mode is ｍ Since depends on the mode, the oscillation wavelength λ ｍ The laser light has different oscillation wavelengths λ ｍ The laser beams λ are superimposed and output from the laser element. ｍ = 2 × Λ × N ｍ (m=0, 1, 2,...) (2)

[0022] Therefore, by providing the diffraction grating 20 in the second portion 2, the spectral linewidth of the semiconductor laser element L1 of the embodiment can be narrowed compared to the above-mentioned example. This allows many components of the laser light to be concentrated in a narrow wavelength range, allowing for efficient use of the laser light output from the semiconductor laser element L1. For example, the laser light output from the semiconductor laser element L1 can be irradiated onto an object via an optical element. The optical element may be, for example, a mirror, a lens, a diffraction grating, or an optical fiber. Since the characteristics of optical elements are wavelength-dependent, it is preferable to use laser light with a narrow spectral linewidth in order to efficiently use the laser light.

[0023] The spectral linewidth may be, for example, 0.01 nm or more and 0.6 nm or less, preferably 0.01 nm or more and 0.5 nm or less, 0.01 nm or more and 0.3 nm or less, or 0.01 nm or more and 0.1 nm or less. In this specification, the spectral linewidth refers to the full width at half maximum. Furthermore, narrowing the spectral linewidth increases the side mode suppression ratio (SMSR). The SMSR may be, for example, 20 dbm or more, preferably 30 dbm or more. This allows the intensity of the laser light to be concentrated at a predetermined wavelength, allowing for efficient use of the laser light output from the semiconductor laser element L1. Furthermore, the SMSR may be 60 dbm or less.

[0024] 1A , the boundary between the first portion 1 and the second portion 2 refers to the line connecting two boundary points P1. One of the two boundary points P1 is a point that is the boundary between the first core region 13 and the first cladding region 11 and also the boundary between the first portion 1 and the second portion 2. The other boundary point P1 is a point that is the boundary between the first core region 13 and the second cladding region 12 and also the boundary between the first portion 1 and the second portion 2.

[0025] When the semiconductor laser element L1 includes the ridge 135, the point P1 may be determined as follows. That is, as shown in Figures 2, 4, and 5, the intersection of the top surface of the p-side semiconductor layer portion 330 on which the ridge 135 is not formed, the first ridge 135a, and the second ridge 135b is determined as the boundary point P1. In other words, the intersection point of the top surface of the p-side semiconductor layer portion 330, the side surface of the first ridge 135a, and the side surface of the second ridge 135b is determined as P1.

[0026] Note that the boundary point P1 can be determined even if the ridge 135 is not formed. For example, when the first portion 1 is a buried heterostructure waveguide, the portion where the width of the active layer 320 increases near the boundary between the first portion 1 and the second portion 2 can be regarded as the boundary point P1. Furthermore, when the first portion 1 is a gain waveguide, the corner of the positive electrode that is in contact with the p-side semiconductor layer portion 330 provided between the first portion 1 and the second portion 2 can be regarded as the boundary point P1.

[0027] The outline of driving the semiconductor laser element L1 has been explained above. Below, individual components will be explained.

[0028] (Semiconductor laminate portion 30) An example of the layer configuration of the semiconductor laminate portion 30 will be described using FIG. 3A. FIG. 3A is a cross-sectional view taken along line IIIA-IIIA in FIG. 2. FIG. 3A is a cross-sectional view parallel to the periodic direction and including the optical axis of the optical waveguide. The semiconductor laminate portion 30 is disposed on the major surface of the substrate 300. The semiconductor laminate portion 30 includes an n-side semiconductor layer portion 310, a p-side semiconductor layer portion 330, and an active layer 320 disposed between the n-side semiconductor layer portion 310 and the p-side semiconductor layer portion 330. As described above, a high-reflection film 62 is provided on the end face on the first portion 1 side (i.e., the second end face 35), and an anti-reflection film 63 is provided on the end face on the second portion 2 side (i.e., the first end face 34). A negative electrode 42 is connected to the substrate 300, and a positive electrode 41 is connected to the p-side semiconductor layer portion 330.

[0029] In the following description, "undoped layer" refers to a semiconductor layer into which no impurities have been intentionally introduced. However, an undoped layer may contain unavoidable impurities. Whether the impurity is an n-type impurity or a p-type impurity, the impurity concentration is 1×10 －１７ cm ―３ The concentration of impurities contained in the undoped layer may be equal to or less than the detection limit of secondary ion mass spectrometry (SIMS).

[0030] (n-side semiconductor layer portion 310) The n-side semiconductor layer portion 310 includes at least one n-type semiconductor layer. The n-side semiconductor layer portion 310 may also include one or more undoped layers. The n-side semiconductor layer portion 310 includes an n-side cladding layer 311 and an n-side optical guide layer 312. The n-side cladding layer 311 is disposed between the substrate 300 and the n-side optical guide layer 312. The thickness of the n-side cladding layer 311 is, for example, 450 nm or more and 3000 nm or less. The concentration of n-type impurities in the n-side cladding layer 311 is, for example, 1×10 －１７ cm ―３ 5x10 or more －１８ cm ―３ The thickness of the n-side light guide layer 312 is, for example, 50 nm or more and 500 nm or less. The concentration of n-type impurities in the n-side light guide layer 312 is, for example, 1×10 －１７ cm ―３5x10 or more －１８ cm ―３ The band gap energy of the n-side optical guiding layer 312 is smaller than the band gap energy of the n-side cladding layer 311 , that is, the refractive index of the n-side optical guiding layer 312 is larger than the refractive index of the n-side cladding layer 311 .

[0031] The n-side semiconductor layer portion 310 is made of, for example, a nitride semiconductor, and may be AlGaN, GaN, InGaN, or the like. The n-side semiconductor layer portion 310 may have a composition between these nitride semiconductors. The n-type impurities contained in the n-side semiconductor layer portion 310 are, for example, Si, Ge, O, or the like.

[0032] (Active Layer 320) The active layer 320 is disposed between the n-side semiconductor layer portion 310 and the p-side semiconductor layer portion 330. The active layer 320 may be a single quantum well layer or a multiple quantum well layer, and includes one or more well layers and two or more barrier layers. The well layer is sandwiched between two barrier layers. The active layer 320 is made of, for example, a nitride semiconductor, such as AlGaN, GaN, or InGaN. The active layer 320 may have a composition between these nitride semiconductors. The active layer 320 emits light when excited by electric current or light. The emitted light has a wavelength of, for example, 360 nm to 570 nm, preferably 380 nm to 450 nm.

[0033] (p-side semiconductor layer portion 330) The p-side semiconductor layer portion 330 includes at least one p-type semiconductor layer. The p-side semiconductor layer portion 330 may also include one or more undoped layers. The p-side semiconductor layer portion 330 includes a first p-side semiconductor layer 331, an electron blocking layer 332, and a second p-side semiconductor layer 333. The electron blocking layer 332 is disposed between the first p-side semiconductor layer 331 and the second p-side semiconductor layer 333. The p-side semiconductor layer portion 330 is made of, for example, a nitride semiconductor, and may be AlGaN, GaN, InGaN, or the like. The p-side semiconductor layer portion 330 may have a composition between these nitride semiconductors. The p-type impurities contained in the p-side semiconductor layer portion 330 are, for example, Mg, Be, or the like.

[0034] (First p-side semiconductor layer 331) The first p-side semiconductor layer 331 is, for example, an undoped layer. Since the peak position of the electric field intensity distribution of light is moved away from the semiconductor layer containing p-type impurities, loss due to light absorption is reduced. The thickness of the first p-side semiconductor layer may be, for example, 200 nm or more and 1000 nm or less, or 300 nm or more and 600 nm or less.

[0035] (Electron Blocking Layer 332) The electron blocking layer 332 is a semiconductor layer having a band gap energy larger than that of the first p-side semiconductor layer 331 and the second p-side semiconductor layer 333. Because the barrier against electrons is large, the loss of electrons in the active layer 320 is reduced. The electron blocking layer 332 may include one or more p-type semiconductor layers. The p-type impurity is, for example, Mg. The concentration of the p-type impurity is, for example, 1×10 １８ cm ―３ 1x10 or more ２０ cm ―３ may be less than or equal to 5×10 １８ cm ―３ 5x10 or more １９ cm ―３ The thickness of the electron blocking layer 332 may be, for example, 5 nm to 30 nm, or 5 nm to 15 nm.

[0036] (Second p-side semiconductor layer 333) The second p-side semiconductor layer 333 is a layer in contact with the positive electrode 41. The second p-side semiconductor layer 333 functions as, for example, an optical guide layer. The second p-side semiconductor layer 333 may include one or more p-type semiconductor layers. The p-type impurity is, for example, Mg. The concentration of the p-type impurity is, for example, 1×10 １８ cm ―３ 1x10 or more １９ cm ―３ The thickness of the second p-side semiconductor layer 333 is, for example, not less than 50 nm and not more than 500 nm. The second p-side semiconductor layer 333 may have a multilayer structure, and the p-type impurity concentration of the second p-side semiconductor layer 333 in contact with the positive electrode 41 may be higher than the p-type impurity concentration of other parts. The p-type impurity concentration of the second p-side semiconductor layer 333 in contact with the positive electrode 41 may be, for example, 1×10 ２０ cm ―３ 1x10 or more ２１ cm―３ The second p-side semiconductor layer 333 may further include a p-side cladding layer, and this p-side cladding layer may be in contact with the positive electrode 41.

[0037] (First Portion 1) The first portion 1 will be described with reference to FIG. 4. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 2. FIG. 4 is a cross-sectional view perpendicular to the optical axis of the optical waveguide. The first portion 1 has a first cladding region 11, a second cladding region 12, and a first core region 13 located between the first cladding region 11 and the second cladding region 12. The first portion 1 is a multi-mode waveguide. The first portion 1 includes at least an n-side semiconductor layer portion 310, an active layer 320, and a p-side semiconductor layer portion 330. In FIG. 4, the first core region 13 is a region including the first ridge 135a, and includes at least the n-side semiconductor layer portion 310, the active layer 320, and the p-side semiconductor layer portion 330. The first cladding region 11 and the second cladding region 12 are regions sandwiching the first ridge 135a, and include at least an n-side semiconductor layer portion 310, an active layer 320, and a p-side semiconductor layer portion 330. The refractive index of the first cladding region 11 is n １１ and the refractive index of the second cladding region 12 is n １１ and the refractive index of the first core region 13 is n １２ The refractive index n １２ is the refractive index n １１ These refractive indices are effective refractive indices taking into consideration the optical confinement in the height direction in the first portion 1. That is, n １１ and n １２ is the equivalent refractive index in the height direction of each region.

[0038] The width of the first core region 13 is a width that forms a multimode waveguide. For example, it is 15 μm or more and 150 μm or less. The width of the first core region 13 is preferably 30 μm or more and 120 μm or less, or 45 nm or more and 100 nm or less. This makes it easier to ensure heat dissipation while controlling the number of transverse modes. The width of the first ridge 135 a may be considered to be the width of the first core region 13.

[0039] The width of the first cladding region 11 may be, for example, 15 μm or more and 500 μm or less. The width of the second cladding region 12 may be, for example, 15 μm or more and 500 μm or less. It is preferable that the width of the first cladding region 11 is substantially the same as the width of the second cladding region 12. This allows the maximum diffusion angle Θ, which will be described later, to be determined. max can be easily adjusted.

[0040] The number of modes excited in the first portion 1 may be, for example, 2 to 500, preferably 10 to 300, and more preferably 30 to 100. This makes it possible to obtain a semiconductor laser device L1 with a high output power.

[0041] (Second portion 2) The second portion 2 will be described with reference to Figures 1A, 3A, 3B, and 5. Figure 3A is a cross-sectional view taken along line IIIA-IIIA in Figure 2, and Figure 3B is a partially enlarged view of the vicinity of the diffraction grating in Figure 3A. Figure 5 is a cross-sectional view taken along line V-V in Figure 2. Figure 5 is a cross-sectional view perpendicular to the periodic direction of the diffraction grating 20. Note that Figure 5 is a cross-sectional view that does not include the first medium 50, but as shown in Figures 3A and 3B, the second portion 2 has the diffraction grating 20 in the p-side semiconductor layer portion 330. The second portion 2 includes at least the n-side semiconductor layer portion 310, the active layer 320, and the p-side semiconductor layer portion 330. The refractive index of the second portion 2 is n ２ This is the effective refractive index that takes into consideration the optical confinement in the stacking direction of the semiconductor stack 30 and averages the modulation of the refractive index of the diffraction grating 20. That is, n ２ is the equivalent refractive index. Refractive index n ２ selects the wavelength of the laser light based on the above-mentioned formula 1.

[0042] 5, the width of the second portion 2 is larger than the width of the core region 13 of the first portion 1. Furthermore, the width of the second portion 2 is larger than the spread of light propagating through the second portion 2. The spread of light in the second portion 2 is determined by the refractive index n １２ and the refractive index n of the first cladding region 1 of the first portion 1. １１ and the refractive index n of the second cladding region 12 of the first portion 1. １１ and the refractive index n of the second portion 2 ２ The maximum diffusion angle Θ is determined bymax The width of the second portion 2 may be equal to or greater than the width of the diffraction grating 20.

[0043] Diffraction Grating 20 As shown in FIGS. 3A and 3B , the diffraction grating 20 is formed by a periodic structure of a p-side semiconductor layer portion 330 and a first medium 50 made of a material different from that of the p-side semiconductor layer portion 330. This provides greater flexibility in selecting the refractive index difference between the p-side semiconductor layer portion 330 and the first medium 50 compared to when a diffraction grating is formed using semiconductors with different mixed crystal ratios. This periodic structure provides the diffraction grating 20 with reflectivity at a predetermined wavelength. As shown in FIG. 3B , the diffraction grating 20 is composed of multiple convex portions 21 provided on the p-side semiconductor layer portion 330 and a first medium 50 disposed between the multiple convex portions 21. The diffraction grating 20 may also be considered to be composed of the first medium 50 disposed in the grooves of multiple concave portions 22 provided on the p-side semiconductor layer portion 330. The first medium 50 is in contact with the side surfaces of the multiple convex portions 21 (or the side surfaces of the multiple concave portions 22).

[0044] The first medium 50 is, for example, at least one selected from the group consisting of air, oxide, fluoride, or nitride. By appropriately selecting the material of the first medium 50, a diffraction grating 20 having a desired reflectance can be obtained. The first medium 50 is preferably an oxide, fluoride, or nitride. This allows the side surfaces of the plurality of protrusions 21 (or the side surfaces of the plurality of recesses 22) to be protected by the first medium 50, thereby reducing deterioration of the p-side semiconductor layer. The oxide may be, for example, ITO, SiO ２ , TiO ２ , or IZO. The fluoride may be, for example, MgF ２ , BaF ２ , or LaF ３ The nitride may be, for example, SiN, SiON, or AlN. The first medium 50 may be ITO or IZO. While reducing deterioration of the side surfaces of the plurality of protrusions 21 (or the side surfaces of the plurality of recesses 22) with ITO or IZO, a current may be efficiently injected into the active layer 320 of the second portion 2, thereby increasing the transmittance of the active layer 320. If there is a risk of leakage from the side surfaces of the plurality of protrusions 21 (or the side surfaces of the plurality of recesses 22), the first medium 50 may be made of SiO ２ , Al２ O ３ , SiN, or SiON, the side surfaces of the convex portions 21 (or concave portions 22) may be protected from leakage while the desired reflectance of the diffraction grating 20 may be obtained.

[0045] The period Λ of the diffraction grating 20 is appropriately determined taking into consideration the wavelength to be selected. The period Λ of the diffraction grating 20 may be, for example, 60 nm to 400 nm, 70 nm to 300 nm, or 80 nm to 250 nm. This increases the reflectance of the desired wavelength.

[0046] The length of the diffraction grating 20 in the periodic direction may be, for example, 50 μm or more and 500 μm or less. This allows a desired reflection band to be obtained. The length of the diffraction grating 20 in the periodic direction is preferably 100 μm or more and 500 μm or less, or 100 μm or more and 300 μm or less. This allows the reflection band to be narrowed and the spectral linewidth of the laser light to be narrowed compared to when the length of the diffraction grating 20 in the periodic direction is less than 100 μm.

[0047] An upper end 201 of the p-side semiconductor layer portion 330 forming the diffraction grating 20 is in contact with the bottom surface of the second medium 55. Hereinafter, the upper end 201 will also be referred to as the upper end 201 of the diffraction grating 20. Similarly, a lower end 202 of the p-side semiconductor layer portion 330 forming the diffraction grating 20 will also be referred to as the lower end 202 of the diffraction grating 20. The second medium 55 may be an oxide. The second medium 55 is, for example, a material for a translucent electrode, and may be ITO or IZO. Both the first medium 50 and the second medium 55 may be translucent electrodes. This allows current to be efficiently injected into the second portion 2, thereby increasing the transmittance of the second portion 2.

[0048] The lower end 202 of the diffraction grating 20 is located in either the second p-side semiconductor layer 333, the electron blocking layer 332, or the first p-side semiconductor layer 331. The lower end 202 of the diffraction grating 20 is preferably located in the first p-side semiconductor layer 331. This brings the diffraction grating 20 closer to the active layer 320, increasing the coupling coefficient between the light and the diffraction grating 20, thereby enabling efficient wavelength selection. Furthermore, when the first medium 50 and the second medium 55 are both light-transmitting electrodes, the lower end 202 of the diffraction grating 20 may be located at least in the electron blocking layer 332. This reduces the possibility of leakage and increases the coupling coefficient. The height difference between the upper end 201 and the lower end 202 of the diffraction grating 20 is, for example, 50 nm or more and 500 nm or less. This allows a desired reflectance to be obtained. The difference in height between the upper end 201 and the lower end 202 of the diffraction grating 20 is preferably 100 nm to 500 nm, 100 nm to 300 nm, or 100 nm to 200 nm, thereby increasing the reflectance compared to when the difference in height between the upper end 201 and the lower end 202 of the diffraction grating 20 is less than 100 nm.

[0049] The diffraction grating 20 has the following characteristics. That is, the longer the length of the diffraction grating 20 in the periodic direction and the greater the difference in height between the upper end 201 and the lower end 202 of the diffraction grating 20, the higher the reflectivity of the diffraction grating 20. Furthermore, the longer the length of the diffraction grating 20 in the periodic direction, the narrower the reflection band. Therefore, in order to obtain a desired reflectivity and reflection band, these must be appropriately set. When the length of the diffraction grating 20 in the periodic direction is 50 μm or more and 500 μm or less, the difference in height between the upper end 201 and the lower end 202 of the diffraction grating 20 may be 50 nm or more and 500 nm or less. Preferably, when the length of the diffraction grating 20 in the periodic direction is 100 μm or more and 300 μm or less, the difference in height between the upper end 201 and the lower end 202 of the diffraction grating 20 may be 100 nm or more and 200 nm or less. This allows for a desired reflection band to be obtained while increasing the reflectivity at a predetermined wavelength.

[0050] The width of the diffraction grating 20 is larger than the width of the first core region 13 of the first portion 1. The width of the diffraction grating 20 may be from 2 to 100 times, or from 2 to 10 times, the width of the first core region 13. By providing the diffraction grating 20 over a range wider than the spread of light propagating through the second portion 2, the variation in equivalent refractive index for each transverse mode is reduced, and the spectral linewidth of the laser light is narrowed. The width of the diffraction grating 20 may be from 30 μm to 9000 μm, from 45 μm to 900 μm, from 45 μm to 500 μm, or from 60 μm to 300 μm.

[0051] As described above, the light in the second portion 2 is diffused at a maximum diffusion angle Θ max 1A, the beam diameter of the laser light at the laser light emitting end face is smaller than the width of the diffraction grating 20, and the distance between both ends of the diffraction grating 20, which corresponds to the width of the diffraction grating 20, may be constant. As a result, the width of the diffraction grating 20 is always larger than the spread of the laser light, so that the variation in the equivalent refractive index for each transverse mode is reduced, and the spectral linewidth of the laser light is narrowed.

[0052] (Cavity) The semiconductor laser element L1 forms a cavity between the high-reflection film 62 of the first portion 1 and the diffraction grating 20 of the second portion 2. The cavity length may be, for example, 500 μm or more and 5000 μm or less. The cavity length may preferably be 1000 μm or more and 5000 μm or less, or 1500 μm or more and 4000 μm or less. This improves the output of the laser light.

[0053] As shown in FIG. 3A , the semiconductor laser element L1 has a region of a predetermined length s between the first end face 34 and the front end 20F of the diffraction grating 20. When the predetermined length s is greater than the period Λ of the diffraction grating 20, a non-wavelength-selective region 25 may be considered to be provided. In this case, the predetermined length s may be, for example, 10 μm to 100 μm, 20 μm to 80 μm, or 30 μm to 60 μm. By providing a distance of length s between the first end face 34 and the front end 20F of the diffraction grating 20, the first end face 34 is less susceptible to the effects of stress on the diffraction grating 20. This may make the anti-reflection film 63 in contact with the first end face 34 less likely to peel off. When the non-wavelength-selective region 25 is provided, the second portion 2 includes the wavelength-selective region 24 and the non-wavelength-selective region 25, as shown in FIG. 1B . The wavelength-selective region 24 is provided with the diffraction grating 20, and the refractive index is n ２ Furthermore, when the predetermined length s is equal to or less than the period Λ of the diffraction grating 20 , this region can be regarded as substantially a part of the diffraction grating 20 .

[0054] (Electrodes) The semiconductor laser device L1 of the embodiment has a positive electrode 41 and a negative electrode 42. The positive electrode 41 is disposed so as to contact at least the p-side semiconductor layer portion 330 in the first portion 1. When the second medium 55 is made of a light-transmitting electrode material such as ITO or IZO, the second medium 55 can be treated as the positive electrode 41. In this case, the bottom surface of the positive electrode 41 contacts the upper end 201 of the diffraction grating 20. The positive electrode 41 may be a single electrode that allows current to be applied simultaneously to the first portion 1 and the second portion 2, or may be a plurality of independent electrodes that allow current to be applied individually to the first portion 1 and the second portion 2. The material of the positive electrode 41 may be, for example, a light-transmitting oxide or a metal. Examples of the light-transmitting oxide include ITO and IZO. Examples of the metal include Ni, Au, Rh, Cr, W, Pt, Ti, Al, or a laminate or alloy thereof. It is preferable that the transparent oxide be in contact with the p-side semiconductor layer portion 330. This reduces loss of light due to absorption by the electrode. An electrode made of metal may be further provided on the transparent oxide. For example, when the substrate 300 is a conductive substrate, the negative electrode 42 may be disposed on the back surface of the substrate 300. Alternatively, an area where the n-side semiconductor layer portion 310 is exposed may be formed, and the negative electrode 42 may be formed on at least a part of this area. The material of the negative electrode 42 may be the same as that of the positive electrode 41.

[0055] (High-Reflection Film, Anti-Reflection Film) The semiconductor laser device L1 of this embodiment has an anti-reflection film 63 on the first end facet 34 and a high-reflection film 62 on the second end facet 35. The anti-reflection film 63 and the high-reflection film 62 may be, for example, a single-layer film of an oxide layer or a nitride layer, or a multilayer film in which multiple oxide layers or nitride layers are stacked in the normal direction of the first end facet 34 or the second end facet 35. The material may be, for example, silicon oxide, aluminum oxide, tantalum oxide, titanium oxide, aluminum nitride, silicon nitride, or gallium nitride.

[0056] (Protective Film) The semiconductor laser element L1 of the embodiment may have a protective film that protects the side surfaces of the semiconductor laminate portion 30. This protects the semiconductor laser element L1 from moisture, sulfide components, etc. The material of the protective film may be, for example, silicon oxide, aluminum oxide, or silicon nitride.

[0057] (maximum diffusion angle Θ max ) Using Figure 6, the maximum diffusion angle Θ max The measurement method for M is explained. ２ 1 is a schematic diagram showing a method for measuring the maximum divergence angle Θ in the semiconductor laser device L1 according to the embodiment. max is an index of the quality of the laser beam given by the following equation 3, M ２ In Equation 3, W ０ is the beam waist radius, φ is the beam divergence angle, and λ is the wavelength of the laser light in vacuum. ２ The factor is an index showing the spread from an ideal Gaussian beam, and in an ideal Gaussian beam, M ２ The factor is 1. That is, the M of the laser light output from the semiconductor laser element L1 ２ Once the factor is known, we can determine how much the laser light is diverging compared to an ideal Gaussian beam, and the maximum divergence angle Θ max Here, the maximum diffusion angle Θ max As shown in FIG. 6 etc., M is the angle formed between a straight line excluding the curved portion in an imaginary line showing the spread of light emitted from the semiconductor laser element L1 and a straight line (shown as a dotted line) extending the boundary between the first core region 13 and the first cladding region 11. ２ =πφW ０ / λ (3)

[0058] Beam waist radius W ０The beam divergence angle φ and the beam divergence angle φ can be measured as follows using an optical system including a collimating lens 81 and a condensing lens 82 shown in Fig. 6. The laser light emitted from the first portion 1 is converted into parallel light by the collimating lens 81 and then condensed by the condensing lens 82, and the trajectory of the condensed laser light is traced. Specifically, the beam diameter of the condensed laser light is measured at various positions Bmp, the position where the beam diameter is smallest is estimated, and the beam waist radius W at that position is calculated. ０ The beam divergence angle φ is calculated by measuring the beam spread from the position where the beam diameter is smallest. ２ The definition of the parameters required to calculate the factor is based on the international standard ISO 11146-1:2021 or ISO 11146-2:2021. The beam diameter is defined as D4σ (second moment width). ２ The current value applied to the semiconductor laser element L1 when measuring the factor is within a predetermined range of operating current. ２ The factors can be measured using a beam profiler.

[0059] Calculated beam waist radius W ０ and the beam divergence angle φ, M is obtained from Equation 3. ２ The factors are calculated and the M ２ The maximum diffusion angle Θ based on the factor max We ask for M ２ Factor and M ２ The trajectory of the laser light emitted from the second portion 2 can be determined from the trajectory of the laser light measured in the process of determining the factor. max By comparing the positional relationship between this imaginary line and both ends of the first portion 1, the spread of the laser light in the first portion 1 can be examined.

[0060] M of the laser beam in embodiment 1 ２ The factor may be, for example, 2 to 100, 5 to 75, or 10 to 50. This makes it possible to obtain a semiconductor laser device L1 with a high laser beam output.

[0061] In addition, when the beam diameter of the laser light at the laser light output end face is smaller than the width of the second portion 2 and the width of the second portion 2 is substantially constant, it is clear that both ends of the second portion 2 are located outside the above-mentioned imaginary line. Therefore, in such a case, if the beam diameter of the laser light at the laser light output end face (i.e., the first end face 34) is first measured, the maximum divergence angle Θ max The positional relationship between the width of the second portion 2 and the imaginary line can be found without calculating the imaginary line that extends.

[0062] As can be understood from the above explanation, the maximum diffusion angle Θ max is an index showing the maximum divergence of the laser light emitted from the first portion 1. The amount of leakage of the laser light beyond the maximum divergence is an amount that does not substantially affect the equivalent refractive index. In other words, the amount of leakage of light is an amount that can be considered to be substantially the same for all transverse modes regardless of the mode order. Therefore, according to the semiconductor laser device L1 of the embodiment, a diffraction grating 20 is provided in the second portion 2, and both ends of the diffraction grating 10 are arranged at a maximum divergence angle Θ max By forming the laser outside the imaginary line based on the above, it is possible to reduce variations in the oscillation wavelength due to differences in the transverse mode and narrow the spectral linewidth.

[0063] As described above, the width of the second portion 2 is set to the maximum diffusion angle Θ max The wavelength selection by the diffraction grating 20 is independent of the transverse mode and substantially the same value. The second portion is preferably a slab waveguide. Since a slab waveguide does not have optical confinement in the width direction, the wavelength selection by the diffraction grating 20 is independent of the transverse mode and substantially the same value.

[0064] (Modification 1) Next, Modification 1 of the semiconductor laser element L1 according to Embodiment 1 will be described. Here, only the changes from Embodiment 1 will be described. Fig. 7 is a top view showing an overview of a semiconductor laser element L11 according to Modification 1. The second portion 2 of the semiconductor laser element L11 has a first end facet 34 from which laser light is emitted, and a normal X1 to the first end facet 34 is inclined with respect to the optical axis of the laser light propagating through the first core region 13 and the direction of the period of the diffraction grating 20 (these directions are jointly represented by axis X2 in Fig. 7). This reduces the influence of returning light that is reflected by the laser light emitting end facet and re-enters the first core region 13.

[0065] As shown in FIG. 7, in the semiconductor laser device L11, the ridge 135a of the first portion 1 is formed at an angle θ ｔ Similarly, the periodic direction of the diffraction grating 20 is tilted by an angle θ ｔ Therefore, the second portion 2 has an asymmetric shape with respect to the normal to the laser light emitting end face in accordance with this inclination. ｔ may be, for example, 1 degree or more and 10 degrees or less.

[0066] Second Embodiment The semiconductor laser element L1 of the first embodiment is configured such that the maximum divergence angle Θ maxA semiconductor laser element L2 according to a second embodiment includes a substrate, a semiconductor laminate including an n-side semiconductor layer, a p-side semiconductor layer, and an active layer disposed between the n-side semiconductor layer and the p-side semiconductor layer, and a positive electrode in contact with the p-side semiconductor layer. The semiconductor laminate includes a first portion having a first cladding region, a second cladding region, and a first core region located between the first cladding region and the second cladding region, and propagating laser light in multiple transverse modes, and a second portion including a diffraction grating. The positive electrode is in contact with at least the first portion of the p-side semiconductor layer. The diffraction grating is provided in the p-side semiconductor layer and includes a periodic structure of the p-side semiconductor layer and a first medium made of a material different from the p-side semiconductor layer, and the upper end of the p-side semiconductor layer forming the diffraction grating is in contact with the bottom surface of the second medium. The second portion has a first end face from which the laser beam is emitted, and the width of the first end face in a direction perpendicular to the direction of the diffraction grating period in top view is larger than the beam diameter of the laser beam at the first end face. In top view, the second portion is also located in a direction away from the central axis of the laser beam, based on the shorter of lines connecting an edge that defines the beam diameter of the laser beam at the first end face and one of both ends of the boundary between the first core region and the second portion.

[0067] By using a diffraction grating that extends beyond the spread of the laser light, a semiconductor laser device with a narrow spectral linewidth of the laser light can be obtained.

[0068] This embodiment will be described with reference to Fig. 8. Fig. 8 is a top view showing an outline of a semiconductor laser device L2 according to embodiment 2. The semiconductor laser device L2 differs from the semiconductor laser device L1 according to embodiment 1 in the following respects.

[0069] In the semiconductor laser element L2, the width of the laser beam at the first end face 34 from which the laser beam is emitted is W2. This width is determined by a virtual line v1a connecting a boundary point P1 between the first core region 13 of the first portion 1 and the second portion 2 and an edge P2 that defines the beam diameter at the first end face 34. The boundary point P1 is the same as point P1 shown in FIG. 2. The shape of the laser beam at the first end face 34 is a near-field pattern, and its width W2 is determined based on D4σ. The width W2 may be determined based on the beam output at the first end face. Alternatively, the width W2 may be determined based on the beam divergence angle in the width direction calculated from the far-field pattern. The width of the second portion 2 at the first end face 34 is W1. This width is determined by a virtual line v1b connecting the edge P3 of the second portion 2 at the first end face 34 to the boundary point P1. The virtual line connecting the edge P2 and the boundary point P1 is connected so as to be as short as possible, as shown in FIG. 8. The imaginary line connecting the end P3 and the boundary point P1 is drawn so as to be the shortest, as shown in FIG. 8. In other words, the boundary point P1 is connected to the end P2 (or end P3) on the same side of the central axis X3 of the laser light. The imaginary line v1b is positioned in a direction away from the central axis X3 of the laser light, using the imaginary line v1a as the reference. As a result, the second portion 2 is always positioned outside the spread of the laser light, so that the refractive index n ２ Therefore, the wavelengths selected by the diffraction grating 20 are substantially the same, resulting in a narrow spectral linewidth.

[0070] 8, the angle θc formed between the side surface S1 of the first ridge 135a and the side surface S2 of the second ridge 135b may be 30° or more and 120° or less, and preferably 45° or more and 110° or less, 80° or more and 100° or less, or 85° or more and 95° or less. This allows the width of the second portion 2 to be maintained larger than the spread of the laser light incident on the second portion 2 from the first portion 1, so that the equivalent refractive index for each transverse mode of the second portion 2 becomes substantially the same. This makes the wavelengths selected by the diffraction grating 20 substantially the same, narrowing the spectral linewidth.

[0071] For example, under the condition that width W1 is larger than width W2, angle θc is set to 90°, and both side surfaces S3 and S4 of second ridge 135b in second portion 2 are parallel to central axis X3 of the laser light. In this case, the width of second portion 2 is always larger than the divergence of the laser light, and the equivalent refractive index for each transverse mode in second portion 2 is substantially the same value.

[0072] <Manufacturing Method> Next, a method for manufacturing the semiconductor laser element L1 according to embodiment 1 will be described. Fig. 9 is a flowchart showing the method for manufacturing the semiconductor laser element L1. The semiconductor laser element L1 includes the steps of: step M1 of preparing a semiconductor laminate in which an n-side semiconductor layer, an active layer 320, and a p-side semiconductor layer are laminated in this order; step M2 of forming a diffraction grating 20 in the p-side semiconductor layer; step M3 of forming a ridge 135; and step M4 of forming a positive electrode 41 on the p-side semiconductor layer.

[0073] This makes it possible to manufacture a semiconductor laser device L1 with a narrow spectral linewidth.

[0074] (Step of Preparing a Semiconductor Stack) First, a semiconductor stack is prepared as shown in FIG. 10 . The semiconductor stack includes a substrate 300, an n-side semiconductor layer portion 310, an active layer 320, and a p-side semiconductor layer portion 330 formed in this order on the substrate 300. The n-side semiconductor layer portion 310 includes an n-side cladding layer 311 and an n-side optical guide layer 312. The p-side semiconductor layer portion 330 includes a first p-side semiconductor layer 331, an electron blocking layer 332, and a second p-side semiconductor layer 333. The electron blocking layer 332 is disposed between the first p-side semiconductor layer 331 and the second p-side semiconductor layer 333. The semiconductor stack may be formed by, for example, chemical vapor deposition (CVD) or physical vapor deposition (PVD). The CVD may be, for example, metal-organic chemical vapor deposition. The PVD method may be a sputtering method or a molecular beam epitaxy method.

[0075] (Step of Forming the Diffraction Grating 20) Next, the diffraction grating 20 is formed on the p-side semiconductor layer portion 330. In this step, as shown in FIG. 11 , a mask 90 material is formed on the p-side semiconductor layer portion 330, and then the mask 90 is patterned into a desired shape. The pattern spacing corresponds to the period of the diffraction grating 20, and is formed at intervals of, for example, 60 nm to 400 nm, 70 nm to 300 nm, or 80 nm to 250 nm. The patterning method may be electron beam lithography, photolithography, nanoimprinting, or the like. When the patterning method is electron beam lithography, a finer mask 90 pattern can be obtained. Furthermore, when the patterning method is nanoimprinting, the mask 90 pattern can be obtained efficiently because it can be patterned all at once. The p-side semiconductor layer portion 330 is processed by etching through the pattern of the mask 90, thereby forming multiple recesses 22 in the p-side semiconductor layer portion 330. Etching is continued until the bottom of the recess 22 is located in any one of the first p-side semiconductor layer 331, the electron blocking layer 332, and the second p-side semiconductor layer 333. Etching is preferably continued until the bottom of the recess 22 is located in the first p-side semiconductor layer 331. This improves the coupling coefficient between light and the diffraction grating 20, allowing for efficient wavelength selection. The multiple recesses 22 are arranged at predetermined intervals. The multiple recesses 22 are formed by dry etching, such as reactive ion etching (RIE). The mask 90 can be made of various resists, Al ２ O ３ , ZrO ２ , SiO ２ , TiO ２ , Ta ２ O ５ The film may be a single layer or a multilayer film of an oxide or nitride such as AlN or SiN, or a metal such as nickel or chromium. The film thickness of these may be, for example, 10 nm or more and 500 nm or less.

[0076] 11, the mask 90 has a portion having a predetermined length s. By making the predetermined length s larger than the patterning interval corresponding to the period of the diffraction grating, the non-wavelength selective region 25 can be formed by etching.

[0077] Next, a first medium 50 having a refractive index different from that of the p-side semiconductor layer portion 330 is formed in the recess 22 formed in the p-side semiconductor layer portion 330. The first medium 50 may be air, an oxide, a fluoride, or a nitride. The first medium 50 may be formed by, for example, a sputtering method, a CVD method, or an atomic layer deposition method (ALD method). The first medium 50 is preferably formed by the ALD method. This allows the recess 22 to be densely filled with the first medium 50, and the diffraction grating 20 to be formed efficiently.

[0078] Next, the mask 90 is removed, and the first medium 50 protruding from the recess 22 is polished to a predetermined thickness. For example, the first medium 50 is polished so that the p-side semiconductor layer and the first medium 50 are substantially flush with each other. This process forms the second portion 2 having the diffraction grating 20 as shown in FIG.

[0079] Forming the diffraction grating 20 in the p-side semiconductor layer portion 330 has the following advantages over, for example, forming the diffraction grating 20 in the n-side semiconductor layer portion 310. First, the shape of the diffraction grating is less likely to be distorted. This is because the diffraction grating 20 is formed without regrowing the semiconductor layer after forming the convex portions 21 (concave portions 22), and therefore the diffraction grating 20 is not damaged by heat generated during the growth of the semiconductor layer. Furthermore, the diffraction grating 20 can be formed after the p-side semiconductor layer portion 330 is stacked and the emission wavelength is checked. This allows the diffraction grating 20 to be formed so that the difference between the actual gain and the design value is adjusted, thereby increasing the yield.

[0080] (Step of forming ridge 135) A mask is formed on the p-side semiconductor layer portion 330, and the ridge 135 is formed by dry etching. The ridge 135 is formed collectively as a first ridge 135a corresponding to the first core region 13 of the first portion 1 and a second ridge 135b corresponding to the second portion 2. Although the ridge 135 is formed up to the second p-side semiconductor layer 333 in Figures 4 and 5, dry etching may be performed up to the first p-side semiconductor layer 331 to form the ridge 135 whose lower end is located in the first p-side semiconductor layer 331.

[0081] (Step of Forming Positive Electrode 41) Next, as shown in FIG. 13 , a positive electrode 41 is formed on the p-side semiconductor layer. The positive electrode 41 can be formed, for example, by sputtering. The material of the positive electrode 41 is at least one selected from metals, translucent oxides, and the like. The material of the positive electrode 41 is preferably a translucent oxide, and may be, for example, ITO. This reduces light absorption in the positive electrode 41. Furthermore, by using ITO as the positive electrode 41, the ITO also functions as a p-side cladding layer. Furthermore, the negative electrode 42 is formed either before or after the step of forming the positive electrode 41.

[0082] (Singulation Step) The manufacturing method of the semiconductor laser element L1 may further include a singulation step. That is, the semiconductor laser element L1 may be obtained by forming a plurality of semiconductor laser element L1 portions on a wafer and then singulating the wafer. The singulation may be performed by cleaving, laser scribing, or the like. Furthermore, when the predetermined length s is greater than the patterning interval corresponding to the diffraction grating period, the semiconductor laminate is cleaved in the non-wavelength-selective region 25 to form the first end facet. Therefore, even if the first end facet is slightly tilted due to cleavage, the diffraction grating 20 is less likely to be affected by this. This allows a diffraction grating 20 having a desired shape to be obtained.

[0083] Next, a semiconductor laser device L3 according to embodiment 3 will be described. The semiconductor laser device L3 differs from the semiconductor laser device L1 in that the first medium 50 and the second medium 55 are at least one insulator selected from the group consisting of oxides, fluorides, and nitrides. The semiconductor laser device L3 having this configuration also provides a semiconductor laser device with a narrow spectral linewidth of laser light.

[0084] The following describes the semiconductor laser device L3, with reference to Figures 14A and 14B, with respect to changes from the semiconductor laser device L1. Figure 14A is a cross-sectional view of the semiconductor laser device. The cross-sectional direction is the same as that of Figure 3A. Figure 14B is an enlarged view of a portion near the diffraction grating in Figure 14A.

[0085] 14A and 14B , a first medium 50 is disposed in the recess 22 provided in the p-side semiconductor layer portion 330. The first medium 50 is at least one insulator selected from the group consisting of oxides, fluorides, and nitrides. This insulates the side surfaces of the recess 22 (or protrusion 21) by the first medium 50, thereby reducing leakage from the side surfaces of the protrusion 21 (or recess 22). Furthermore, when the first medium 50 is made of an insulator, it is preferable that the bottom surface of the recess 22 be located in the first p-side semiconductor layer 331. This improves the coupling efficiency between light and the diffraction grating 20, enabling efficient wavelength selection.

[0086] (Second Medium 55) The upper end 201 of the p-side semiconductor layer portion 330 forming the diffraction grating 20 is in contact with the bottom surface of the second medium 55. The second medium 55 is at least one insulator selected from the group consisting of oxides, fluorides, and nitrides. Since the second portion 2 is insulated by the first medium 50 and the second medium 55, the current path is concentrated in the first portion 1. This reduces the current injected into portions outside the beam diameter that do not contribute to light emission, thereby reducing reactive current and improving WPE (wall plug efficiency). Furthermore, since no refractive index distribution in the width direction due to current injection occurs in the second portion 2, the stability of wavelength selection by the diffraction grating 20 is improved. The thickness of the second medium 55 may be any thickness that can insulate the current injected into the second portion. The thickness of the second medium 55 may be, for example, 20 nm to 200 nm.

[0087] In the semiconductor laser element L3, for example, the length in the X direction of the first portion 1 may be 1000 μm or more and 5000 μm or less, and the length in the X direction of the second portion 2 may be 50 μm or more and 500 μm or less. This makes the length in the X direction of the second portion 2 sufficiently shorter than the length in the X direction of the first portion 1, thereby reducing the amount of reduction in output power due to light absorption caused by insulating the second portion 2. In the semiconductor laser element L3, for example, the length in the X direction of the first portion 1 may be preferably 2500 μm or more and 5000 μm or less, and the length in the X direction of the second portion 2 may be preferably 100 μm or more and 300 μm or less.

[0088] The lower end of the second medium 55 may be in contact with the upper end of the first medium 50. The first medium 50 and the second medium 55 may be made of the same material. Alternatively, the first medium 50 and the second medium 55 may be an integrated member. This allows the side surfaces of the recessed portion 22 (or the protruding portion 21) to be continuously covered, and part of the upper end 201 of the p-side semiconductor layer portion 330, thereby effectively reducing leakage current.

[0089] 14A and 14B , the second medium 55 may be formed so as to overlap a part of the upper surface of the positive electrode 41, the side surface of the positive electrode 41, and the upper end 201 of the p-side semiconductor layer portion 330 exposed from the positive electrode 41. This reduces the possibility that the upper surface of the p-side semiconductor layer portion 330 will come into contact with air. Therefore, the p-side semiconductor layer portion 330 is protected, and the life of the semiconductor laser element L3 is increased.

[0090] (Pad electrode 43) The semiconductor laser element L3 further has a pad electrode 43. The pad electrode 43 is provided on the upper surfaces of the positive electrode 41 and the second medium 55. In this embodiment, the second medium 55 is an insulator, and current is injected into the first portion 1 from the portion where the positive electrode 41 is provided.

[0091] <Manufacturing Method> Next, an example of a manufacturing method for the semiconductor laser device L3 will be described. In this example, a method of forming the first medium 50 and the second medium 55 as an integrated member using the same material will be described.

[0092] First, as shown in FIG. 15 , a plurality of recesses 22 (or a plurality of protrusions 21) are formed in the p-side semiconductor layer portion 330 of the semiconductor laminate. The manufacturing method of the semiconductor laser element L3 is the same as that of the semiconductor laser element L1 up to the step of forming a plurality of recesses 22 (or a plurality of protrusions 21) in the p-side semiconductor layer portion 330. That is, first, a semiconductor laminate is prepared in which a substrate 300, an n-side semiconductor layer portion 310 disposed on the substrate 300, an active layer 320, and a p-side semiconductor layer portion 330 are formed in this order. Next, the p-side semiconductor layer portion 330 is etched via a mask to form a plurality of recesses 22. The etching is continued until the bottom of the recess 22 is located in any one of the first p-side semiconductor layer 331, the electron blocking layer 332, and the second p-side semiconductor layer 333. In the example of FIG. 15 , the bottom of the recess 22 is located in the first p-side semiconductor layer 331. After the recess 22 is formed, a ridge 135 is formed.

[0093] 16 , a positive electrode 41 is formed on the top surface of the p-side semiconductor layer portion 330. The positive electrode 41 is patterned and provided so as to allow current to flow through a portion of the first portion 1 corresponding to the first core region 13.

[0094] Next, as shown in FIGS. 17A and 17B , the first medium 50 and the second medium 55 are formed inside the recess 22, on the top surface of the p-side semiconductor layer portion 330, and on the side and top surfaces of the positive electrode 41. FIG. 17B is a partial enlarged view of the diffraction grating and its vicinity in FIG. 17A . In this example, the first medium 50 and the second medium 55 are integrally formed from the same material. The first medium 50 and the second medium 55 can be formed by a sputtering method, a CVD method, an ALD method, or the like. The first medium 50 and the second medium 55 are preferably formed by an ALD method. This allows the recess 22 to be densely filled with the first medium 50, thereby efficiently forming the diffraction grating 20. Furthermore, since the top surface to the side surface of the positive electrode 41, the top surface of the p-side semiconductor layer portion 330, and the side surface to the bottom surface of the recess 22 are continuously covered by the first medium 50 or the second medium 55, the p-side semiconductor layer portion 330 is less likely to be exposed from the first medium 50 and the second medium 55, and deterioration of the p-side semiconductor layer portion 330 due to exposure to air is less likely to occur.

[0095] 18 , a part of the first portion 1 and the second portion 2 are protected with a mask 95, and unnecessary portions of the second medium 55 are removed from the positive electrode 41. This makes it possible to integrally cover the first medium 50 and the second medium 55 from a part of the top surface of the positive electrode 41 to the side surface of the positive electrode 41, the top end 201 of the p-side semiconductor layer portion 330, and the inside of the recess 22.

[0096] 19 , the mask 95 is removed, and the pad electrode 43 is formed on the upper surface of the positive electrode 41 and the upper surface of the second medium 55. Furthermore, the negative electrode 42 is formed. The negative electrode 42 may be formed on the back surface of the substrate 300, as shown in FIG. 19 . Alternatively, a part of the n-side semiconductor layer portion 310 of the first portion 1 may be exposed from the active layer 320 and the p-side semiconductor layer portion 330, and the negative electrode 42 may be formed on that part.

[0097] Next, the semiconductor laminate is cleaved, and after forming a high-reflection film 62 and an anti-reflection film 63, the semiconductor laminate is singulated to obtain a semiconductor laser element L3 as shown in FIG. 14A.

[0098] 20 is a partially enlarged view of the vicinity of the diffraction grating of a semiconductor laser element of Modification 2. As described in Embodiment 1, the lower end 202 of the diffraction grating 20 is located in any one of the second p-side semiconductor layer 333, the electron blocking layer 332, or the first p-side semiconductor layer 331. In Modification 2, the lower end 202 of the diffraction grating 20 is located in the second p-side semiconductor layer 333. This makes it possible to further reduce the possibility of leakage. In other respects, this is the same as the semiconductor laser element L1 of Embodiment 1.

[0099] In the periodic direction, the length a of the recesses 22 of the diffraction grating 20 may be 0.6 to 1.3 times the length b of the protrusions 21. This increases the reflectance of the diffraction grating 20. In the periodic direction, the length a of the recesses 22 of the diffraction grating 20 is preferably 0.8 to 1.2 times, 0.95 to 1.05 times, or 0.98 to 1.02 times the length b of the protrusions 21. This increases the reflectance of the diffraction grating 20. The closer the length a of the recesses 22 is to 1 time the length b of the protrusions 21, the higher the reflectance of the diffraction grating 20.

[0100] In the height direction, the height h of the diffraction grating 20 may be 0.1 to 10 times the length b of the recesses 22. The height h of the diffraction grating 20 may also be 0.8 to 2 times, preferably 0.9 to 1.1 times, and more preferably 0.95 to 1.05 times the length b of the recesses 22. By bringing the aspect ratio (h / b) of the height h of the diffraction grating 20 to the length b of the recesses 22 closer to 1, the difference between the equivalent refractive index in the height direction of the region including the recesses 22 and the equivalent refractive index in the height direction of the region including the protrusions 21 can be reduced. This narrows the reflection band of the diffraction grating 20 and narrows the spectral linewidth of the laser light. The aspect ratio (h / a) of the height h of the diffraction grating 20 to the length a of the protrusions 21 may also be within a similar range.

[0101] The diffraction grating 20 is preferably formed by dry etching a mask patterned by nanoimprinting, which allows patterning while maintaining the desired spacing between the recesses 22 and protrusions 21, as compared to electron beam lithography.

[0102] Fourth Embodiment As a fourth embodiment, the semiconductor laser element L1 of the first embodiment is configured such that the maximum divergence angle Θ max A fourth embodiment will be described, which specifies the configuration without using the term "reflector." The semiconductor laser device of the fourth embodiment includes a substrate, a semiconductor laminate including an n-side semiconductor layer portion, a p-side semiconductor layer portion, and an active layer disposed between the n-side semiconductor layer portion and the p-side semiconductor layer portion, and a positive electrode in contact with the p-side semiconductor layer portion. The semiconductor laminate includes a first portion that is a channel waveguide and a second portion that is a slab waveguide. The first portion is a multi-mode waveguide, and the second portion includes a diffraction grating. The positive electrode is in contact with at least the first portion of the p-side semiconductor layer portion. The diffraction grating is provided in the p-side semiconductor layer portion and includes a periodic structure of the p-side semiconductor layer portion and a first medium made of a material different from the p-side semiconductor layer portion, and the upper end of the p-side semiconductor layer portion forming the diffraction grating is in contact with the bottom surface of the second medium.

[0103] By using a diffraction grating that extends beyond the spread of the laser light, a semiconductor laser device with a narrow spectral linewidth of the laser light can be obtained.

[0104] A semiconductor laser device of embodiment 4 will be described with reference to FIG. 1A. As described above, in the semiconductor laser device L1 of FIG. 1A, the first portion 1 is a multimode waveguide, and multiple transverse modes are guided and enter the second portion 2. The first portion 1 can be regarded as a channel waveguide. Furthermore, both ends of the second portion 2 in the width direction are spaced apart by a maximum divergence angle Θ from the boundary between the first portion 1 and the second portion 2, indicated by point P1 in FIG. 1A. max The second portion 2 is located outside the imaginary line extending in a direction perpendicular to the optical axis. Since the second portion 2 can be regarded as having no optical confinement in the width direction for the light guided through the second portion 2, the second portion 2 may also be called a slab waveguide. By providing the diffraction grating 20 in such a second portion 2, a semiconductor laser device with a narrow spectral linewidth of laser light can be obtained.

[0105] The semiconductor materials constituting the semiconductor laser elements L1, L11, L2, and L3 and the semiconductor laser element of embodiment 4 described so far may be materials other than nitride semiconductors. The semiconductor materials may be, for example, GaAs, InP, GaInP, GaInAsP, AlGaAs, InAlAs, or AlInGaP. In this case, the semiconductor laser elements L1, L11, L2, and L3 and the semiconductor laser element of embodiment 4 may have an oscillation wavelength of 760 nm or more and 1700 nm or less. Furthermore, the semiconductor laser elements L1, L11, L2, and L3 and the semiconductor laser element of embodiment 4 may be made of materials other than these. For example, aluminum nitride or boron nitride may be used to constitute the semiconductor laser elements L1, L11, L2, and L3 and the semiconductor laser element of embodiment 4 that emit ultraviolet light.

[0106] <Application Example 1> The semiconductor laser element L1 of the present disclosure can be used, for example, in a wavelength beam combining (WBC) device 1000. The same applies to the semiconductor laser elements L11, L2, and L3 and the semiconductor laser element of embodiment 4. Here, the semiconductor laser element L1 will be used as an example. The WBC device 1000 combines multiple laser beams with different oscillation wavelengths to obtain a laser beam with a higher output. The semiconductor laser element L1 of the present disclosure is a transverse multimode semiconductor laser element L1 and has a high output. Furthermore, since the semiconductor laser element L1 has a diffraction grating 20 in the second portion 2, the spectral linewidth of the laser beam is narrow. Therefore, by using multiple semiconductor laser elements L1 with different oscillation wavelengths in the WBC device 1000, multiple laser beams can be efficiently combined, thereby increasing the output of the WBC device 1000.

[0107] FIG. 21 is a schematic diagram illustrating a WBC device 1000. The WBC device 1000 includes multiple light source units 1100 and a beam combining optical system 1200. Each of the multiple light source units 1100 includes a semiconductor laser element L1 according to the present disclosure and a collimating lens 1101 disposed at a position where the laser light emitted from the semiconductor laser element L1 is incident. The peak wavelengths of the laser light emitted from each light source unit 1100 are different. The beam combining optical system 1200 combines the laser light emitted from the multiple light source units 1100. This increases the output of the WBC device 1000. The configuration of the WBC device 1000 will be briefly described below.

[0108] Each of the light source units 1100 includes a semiconductor laser element L1 according to the present disclosure and a collimator lens 1101. The peak wavelength of the output laser light differs for each light source unit 1100. １ , λ ２ , ...λ ｑThe notation (q = 1, 2, 3, ...) means that the peak wavelengths of the laser beams output from the semiconductor laser elements L1 are different. When comparing the wavelengths of two laser beams with the closest peak wavelengths among the laser beams output from the multiple light source units 1100, the difference between their peak wavelengths is, for example, 0.3 nm or more and 3 nm or less, preferably 0.3 nm or more and 1.5 nm or less, and more preferably 0.3 nm or more and 1 nm or less. This allows the laser beams to be efficiently combined within the band of the beam combining optical system 1200. The collimating lens 1101 collimates the fast axis and / or slow axis components of the laser beams output from the semiconductor laser elements L1. Note that collimation in this application example also includes deviation from perfectly parallel beams within a range of ±10 mrad or less. Furthermore, each light source unit 1100 does not need to consist of only one pair of semiconductor laser element L1 and collimating lens 1101, and may include multiple pairs. As a result, the output of the laser light having the oscillation wavelength λq output from each light source unit 1100 increases.

[0109] In the following, a case where the beam-combining optical system 1200 is a diffraction grating will be described. The diffraction grating satisfies the following formula 4: α ｑ is the oscillation wavelength λ ｑ is the incident angle of the laser beam, β is the diffraction angle, G is the number of grooves in the diffraction grating, and l is the order. q + sinβ = Glλ q (4)

[0110] The laser beams emitted from the plurality of light source units 1100 enter the beam combining optical system 1200 at different angles and are combined at a diffraction angle β.

[0111] 21, a first diffraction grating 1201a and a second diffraction grating 1201b are arranged in parallel to form a pair, forming a beam-combining optical system 1200. The laser beams output from the light source units 1100 are incident on the first diffraction grating 1201a with their optical axes parallel to each other. The laser beams diffracted by the first diffraction grating 1201a are incident at an incident angle α １ , α ２ , ...α ｑThe laser beam is incident on a predetermined position of the second diffraction grating 1201b and diffracted at a diffraction angle β. When focusing on one of the light source units 1100, the laser beam output from the light source unit 1100 has a narrow spectral linewidth, so many components of the laser beam are diffracted at a diffraction angle β. Therefore, the WBC device 1000 efficiently combines the laser beams to obtain a high-output laser beam. The combined laser beam is coupled to, for example, a multimode fiber. The core diameter of the multimode fiber is, for example, 90 μm or more and 400 μm or less. Note that the combining optical system 1200 is not limited to a diffraction grating, and may be a wavelength-dependent optical element such as a dichroic mirror.

[0112] Example 1 The semiconductor laser element of Example 1 was fabricated as the semiconductor laser element of Embodiment 1. The semiconductor laser element of Example 1 was obtained by stacking an n-side semiconductor layer portion, an active layer, and a p-side semiconductor layer portion on a GaN substrate. The width of the first ridge was 90 μm, and the width of the second ridge was 345 μm. The diffraction grating had a periodic structure of the second portion of the p-side semiconductor layer portion and air, and the period of the diffraction grating was 94.1 nm. An ITO positive electrode was formed on the upper end of the p-side semiconductor layer portion, and the bottom surface of the positive electrode was in contact with the upper end of the diffraction grating.

[0113] Comparative Example 1 A semiconductor laser device was fabricated as Comparative Example 1. The semiconductor laser device of Comparative Example 1 differs from the semiconductor laser device of Example 1 in that it does not have a second portion and has a transverse multimode waveguide with a ridge width of 90 μm.

[0114] Reference Example 1 A semiconductor laser element of Reference Example 1 was fabricated. The semiconductor laser element of Reference Example 1 differs from the semiconductor laser element of Example 1 in that a diffraction grating is provided inside the n-side semiconductor layer portion and has a periodic structure of semiconductor layers with different mixed crystal ratios. In the semiconductor laser element of Reference Example 1, the period of the diffraction grating was set to 94.6 nm.

[0115] First, the spectral linewidths of the semiconductor laser elements of Example 1, Reference Example 1, and Comparative Example 1 were measured. The spectral linewidths of the semiconductor laser elements of Example 1 and Reference Example 1 were measured using a spectrum analyzer. The spectral linewidth of the semiconductor laser element of Comparative Example 1 was measured using a spectroscope. FIG. 22 is a diagram showing the spectra of the semiconductor laser elements when a current of 9.5 A was applied. The solid line is the spectrum of Example 1, the dotted line is the spectrum of Reference Example 1, and the dash-dotted line is the spectrum of Comparative Example 1. FIG. 22 shows that the spectral linewidths of the semiconductor laser elements of Example 1 and Reference Example 1 were narrower than that of the semiconductor laser element of Comparative Example 1. Furthermore, FIG. 22 confirms that the spectral linewidths of both Example 1 and Reference Example 1 were 0.2 nm or less, and that both had relatively narrow spectral linewidths.

[0116] Next, the relationship between the input current and the output power was investigated for the semiconductor laser elements of Example 1, Comparative Example 1, and Reference Example 1. The input current value was 9.5 A. The outputs from the semiconductor laser elements of Example 1, Comparative Example 1, and Reference Example 1 were 14.9 W, 15.2 W, and 13.5 W, respectively. From these results, it was confirmed that the semiconductor laser elements of Example 1 and Reference Example 1, despite having a diffraction grating, were able to obtain an output power close to that of the semiconductor laser element of Comparative Example 1, which does not have a diffraction grating. Furthermore, the semiconductor laser element of Example 1 obtained a higher output power than the semiconductor laser element of Reference Example 1.

[0117] The present disclosure includes the following configuration: (Item 1) A semiconductor laminate including a substrate, an n-side semiconductor layer portion, a p-side semiconductor layer portion, and an active layer disposed between the n-side semiconductor layer portion and the p-side semiconductor layer portion, and a positive electrode in contact with the p-side semiconductor layer portion, wherein the semiconductor laminate includes: a first portion having a first cladding region, a second cladding region, and a first core region located between the first cladding region and the second cladding region, and propagating laser light in a plurality of transverse modes, and a second portion including a diffraction grating, wherein the positive electrode is in contact with the p-side semiconductor layer portion in at least the first portion, the diffraction grating is provided in the p-side semiconductor layer portion, and includes a periodic structure of the p-side semiconductor layer portion and a first medium made of a material different from the p-side semiconductor layer portion, and an upper end of the p-side semiconductor layer portion forming the diffraction grating is in contact with a bottom surface of a second medium, The laser light emitted from the first portion has a maximum divergence angle Θ determined by the refractive index of the first core region, the refractive index of the first cladding region, the refractive index of the second cladding region, and the refractive index of the second portion. max When viewed from above, both ends of the second portion in a direction perpendicular to the optical axis of the laser light are spaced apart from the boundary between the first portion and the second portion by the maximum divergence angle Θ maxa semiconductor laser element positioned outside an imaginary line extending as follows: (Item 2) A semiconductor laser element comprising: a substrate; a semiconductor laminate having an n-side semiconductor layer portion, a p-side semiconductor layer portion, and an active layer disposed between the n-side semiconductor layer portion and the p-side semiconductor layer portion; and a positive electrode in contact with the p-side semiconductor layer portion, wherein the semiconductor laminate comprises: a first portion having a first cladding region, a second cladding region, and a first core region disposed between the first cladding region and the second cladding region, and propagating laser light in a plurality of transverse modes; and a second portion including a diffraction grating, wherein the positive electrode is in contact with the p-side semiconductor layer portion in at least the first portion, the diffraction grating is provided in the p-side semiconductor layer portion, and includes a periodic structure of the p-side semiconductor layer portion and a first medium made of a material different from that of the p-side semiconductor layer portion, an upper end of the p-side semiconductor layer portion forming the diffraction grating is in contact with a bottom surface of a second medium, and the second portion has a first end face for emitting laser light, a semiconductor laser element in which, in top view, a width of the first end face in a direction orthogonal to a direction of the periodicity of the diffraction grating is larger than a beam diameter of the laser light at the first end face, and in top view, the second portion is also located in a direction away from a central axis of the laser light, based on a shorter line connecting an edge that defines the beam diameter of the laser light at the first end face and one of both ends of a boundary between the first core region and the second portion. (Item 3) A semiconductor laser element comprising: a substrate; a semiconductor laminate having an n-side semiconductor layer portion, a p-side semiconductor layer portion, and an active layer disposed between the n-side semiconductor layer portion and the p-side semiconductor layer portion; and a positive electrode in contact with the p-side semiconductor layer portion, wherein the semiconductor laminate portion comprises: a first portion which is a channel waveguide; and a second portion which is a slab waveguide, wherein the first portion is a multi-mode waveguide, and the second portion includes a diffraction grating, the positive electrode is in contact with at least the p-side semiconductor layer portion in the first portion, the diffraction grating is provided in the p-side semiconductor layer portion, and includes a periodic structure of the p-side semiconductor layer portion and a first medium made of a material different from that of the p-side semiconductor layer portion, and an upper end of the p-side semiconductor layer portion forming the diffraction grating is in contact with a bottom surface of the second medium.(Item 4) The semiconductor laser element according to any one of Items 1 to 3, wherein the p-side semiconductor layer portion has a first p-side semiconductor layer, a second p-side semiconductor layer, and an electron blocking layer disposed between the first p-side semiconductor layer and the second p-side semiconductor layer, the first p-side semiconductor layer being disposed between the active layer and the electron blocking layer, and a lower end of the diffraction grating being located in the first p-side semiconductor layer. (Item 5) The semiconductor laser element according to any one of Items 1 to 4, wherein the first medium and the second medium are both light-transmitting electrodes. (Item 6) The semiconductor laser element according to any one of Items 1 to 5, wherein the first medium and the second medium are at least one insulator selected from the group consisting of oxides, fluorides, and nitrides. (Item 7) The semiconductor laser element according to any one of Items 1 to 6, wherein the length of the diffraction grating in the periodic direction of the diffraction grating is 50 μm or more and 500 μm or less. (Item 8) The semiconductor laser element according to any one of Items 1 to 7, wherein a difference in height between the upper end and the lower end of the diffraction grating in the stacking direction of the semiconductor stack is 50 nm or more and 500 nm or less. (Item 9) The semiconductor laser element according to any one of Items 1 to 8, wherein a width of the diffraction grating is 2 to 100 times the width of the first core region. (Item 10) The semiconductor laser element according to any one of Items 1 to 9, wherein a width of the first core region is 15 μm or more and 150 μm or less, and a width of the diffraction grating is 30 μm or more and 9000 μm or less. (Item 11) The semiconductor laser element according to any one of Items 1 to 10, wherein a normal to a first end face of the second portion is inclined with respect to the optical axis of laser light propagating through the first core region and the direction of the periodicity of the diffraction grating. (Item 12) A wavelength beam combining device comprising: a plurality of light source units; and a combining optical system, wherein each of the plurality of light source units has a semiconductor laser element according to any one of items 1 to 11; and a collimating lens provided at a position where laser light emitted from the semiconductor laser element is incident, wherein a peak wavelength of the laser light differs for each of the plurality of light source units, and the combining optical system combines the laser light emitted from the plurality of light source units.

[0118] This application claims priority based on Japanese Patent Application No. 2024-057627 filed in Japan on March 29, 2024, and Japanese Patent Application No. 2024-188596 filed in Japan on October 25, 2024, the entire contents of which are incorporated herein by reference.

[0119] L1, L2, L3, L11 Semiconductor laser element 1 First portion 11 First cladding region 12 Second cladding region 13 First core region 2 Second portion 20 Diffraction grating 21 Convex portion 22 Concave portion 24 Wavelength selection region 25 Non-wavelength selection region 30 Semiconductor laminate portion 300 Substrate 310 N-side semiconductor layer portion 311 N-side cladding layer 312 N-side optical guide layer 320 Active layer 330 P-side semiconductor layer portion 331 First p-side semiconductor layer 332 Electron blocking layer 333 Second p-side semiconductor layer 34 First end face 35 Second end face 41 Positive electrode 42 Negative electrode 43 Pad electrode 50 First medium 55 Second medium 62 Highly reflective film 63 Anti-reflection film 70 Insulating layer 81 Collimating lens 82 Condenser lens 90 Mask 95 Mask 135 Ridge 135a First ridge 135b Second ridge 1000 Wavelength beam combining device 1100 Light source section 1101 Collimating lens 1200 Wave combining optical system 1201a First diffraction grating 1201b Second diffraction grating

Claims

1. A semiconductor laminate having a substrate, an n-side semiconductor layer, a p-side semiconductor layer, and an active layer disposed between the n-side semiconductor layer and the p-side semiconductor layer, and a positive electrode in contact with the p-side semiconductor layer, wherein the semiconductor laminate comprises: a first portion having a first cladding region, a second cladding region, and a first core region located between the first cladding region and the second cladding region, and propagating laser light in a plurality of transverse modes; and a second portion including a diffraction grating, wherein the positive electrode is in contact with the p-side semiconductor layer in at least the first portion, the diffraction grating is provided in the p-side semiconductor layer and includes a periodic structure of the p-side semiconductor layer and a first medium made of a material different from that of the p-side semiconductor layer, and an upper end of the p-side semiconductor layer forming the diffraction grating is in contact with a bottom surface of a second medium, The laser light emitted from the first portion has a maximum divergence angle Θ determined by the refractive index of the first core region, the refractive index of the first cladding region, the refractive index of the second cladding region, and the refractive index of the second portion. max When viewed from above, both ends of the second portion in a direction perpendicular to the optical axis of the laser light are spaced apart from the boundary between the first portion and the second portion by the maximum divergence angle Θ max A semiconductor laser element located outside the imaginary line extending from the center.

2. A laser diode comprising: a substrate; a semiconductor laminate having an n-side semiconductor layer, a p-side semiconductor layer, and an active layer disposed between the n-side semiconductor layer and the p-side semiconductor layer; and a positive electrode in contact with the p-side semiconductor layer, wherein the semiconductor laminate comprises: a first portion having a first cladding region, a second cladding region, and a first core region located between the first cladding region and the second cladding region, and propagating laser light in a plurality of transverse modes; and a second portion including a diffraction grating, wherein the positive electrode is in contact with the p-side semiconductor layer in at least the first portion, the diffraction grating is provided in the p-side semiconductor layer and includes a periodic structure of the p-side semiconductor layer and a first medium made of a material different from that of the p-side semiconductor layer, an upper end of the p-side semiconductor layer forming the diffraction grating is in contact with a bottom surface of the second medium, and the second portion has a first end face for emitting laser light, a semiconductor laser element in which, in top view, a width of the first end face in a direction orthogonal to a direction of the periodicity of the diffraction grating is larger than a beam diameter of the laser light at the first end face, and in top view, the second portion is also located in a direction away from a central axis of the laser light, based on a shorter line connecting an edge that defines the beam diameter of the laser light at the first end face and one of both ends of a boundary between the first core region and the second portion.

3. The semiconductor laser element according to claim 1 or 2, wherein the p-side semiconductor layer portion has a first p-side semiconductor layer, a second p-side semiconductor layer, and an electron blocking layer disposed between the first p-side semiconductor layer and the second p-side semiconductor layer, the first p-side semiconductor layer is disposed between the active layer and the electron blocking layer, and the lower end of the diffraction grating is located in the first p-side semiconductor layer.

4. The semiconductor laser device according to any one of claims 1 to 3, wherein the first medium and the second medium are both optically transparent electrodes.

5. A semiconductor laser device according to any one of claims 1 to 4, wherein the first medium and the second medium are at least one insulator selected from the group consisting of oxides, fluorides, and nitrides.

6. The semiconductor laser device according to claim 1, wherein the length of said diffraction grating in the periodic direction of said diffraction grating is not less than 50 μm and not more than 500 μm.

7. The semiconductor laser device according to claim 1, wherein the difference in height between the upper end and the lower end of the diffraction grating in the stacking direction of the semiconductor stacked portion is 50 nm or more and 500 nm or less.

8. The semiconductor laser device according to any one of claims 1 to 7, wherein the width of the diffraction grating is at least two times but not more than 100 times the width of the first core region.

9. A semiconductor laser device according to any one of claims 1 to 8, wherein the width of the first core region is 15 μm or more and 150 μm or less, and the width of the diffraction grating is 30 μm or more and 9000 μm or less.

10. A semiconductor laser element according to any one of claims 1 to 9, wherein the second portion has a first end face from which the laser light is emitted, and a normal to the first end face is inclined with respect to the optical axis of the laser light propagating through the first core region and the direction of the period of the diffraction grating.

11. A semiconductor laser device comprising: a substrate; a semiconductor laminate having an n-side semiconductor layer portion, a p-side semiconductor layer portion, and an active layer disposed between the n-side semiconductor layer portion and the p-side semiconductor layer portion; and a positive electrode in contact with the p-side semiconductor layer portion, wherein the semiconductor laminate portion comprises: a first portion which is a channel waveguide; and a second portion which is a slab waveguide, wherein the first portion is a multi-mode waveguide and the second portion includes a diffraction grating, the positive electrode in contact with at least the p-side semiconductor layer portion in the first portion, the diffraction grating being provided in the p-side semiconductor layer portion and including a periodic structure of the p-side semiconductor layer portion and a first medium made of a material different from that of the p-side semiconductor layer portion, and an upper end of the p-side semiconductor layer portion forming the diffraction grating in contact with a bottom surface of the second medium.

12. A wavelength beam combining device comprising a plurality of light source units and a combining optical system, wherein each of the plurality of light source units has a semiconductor laser element according to any one of claims 1 to 11, and a collimating lens provided at a position where laser light emitted from the semiconductor laser element is incident, wherein the peak wavelength of the laser light differs for each of the plurality of light source units, and the combining optical system combines the laser light emitted from the plurality of light source units.

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