Semiconductor laser element

Abstract

The present invention provides a transverse multimode semiconductor laser element with small variation in oscillation wavelength. [Solution] The semiconductor layer 3 comprises a substrate 2 and a waveguide 50 including an active layer, and is disposed on the substrate. The waveguide includes a wide section 54 equipped with a diffraction grating and a narrow section 53 which has a narrower waveguide width than the wide section and in which light generated in the active layer propagates in transverse multimode. The waveguide includes a first end face 51 which includes the end face of the narrow section and a second end face 52 located on the opposite side of the first end face. The wide section is continuously connected to the narrow section and includes a first region 55 in which the waveguide width widens from the first end face side to the second end face side.

Description

[Technical Field]

[0001] This disclosure relates to semiconductor laser devices. [Background technology]

[0002] In recent years, with the diversification of applications for semiconductor laser elements, there has been a growing demand for transverse multimode semiconductor laser elements, which tend to produce higher power outputs than transverse single-mode semiconductor laser elements. For example, Patent Document 1 discloses a transverse multimode semiconductor laser element. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2011-151238 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, the transverse multimode semiconductor laser element disclosed in Patent Document 1 has a large variation in the longitudinal modes, that is, a large variation in the oscillation wavelength.

[0005] Therefore, the present disclosure aims to provide a transverse multimode semiconductor laser element with small variation in oscillation wavelength. [Means for solving the problem]

[0006] A semiconductor laser element according to one embodiment of the present disclosure comprises a substrate and a semiconductor layer portion disposed on the substrate, the semiconductor layer portion comprising a waveguide including an active layer, wherein the waveguide includes a wide portion comprising a diffraction grating and a narrow portion having a narrower waveguide width than the wide portion and through which light generated in the active layer propagates in transverse multimode, the waveguide includes a first end face including the end face of the narrow portion and a second end face located on the opposite side of the first end face, and the wide portion comprises a first region continuously connected to the narrow portion, the waveguide width widening from the first end face side to the second end face side. [Effect of the Invention]

[0007] The semiconductor laser device according to one embodiment of the present disclosure can provide a transverse multimode semiconductor laser device with small variation in oscillation wavelength. [Brief Description of the Drawings]

[0008] [Figure 1] It is a schematic top view of the semiconductor laser device according to Embodiment 1 of the present disclosure. [Figure 2] It is a schematic cross-sectional view taken along line II-II of the semiconductor laser device shown in FIG. 1. [Figure 3] It is a schematic cross-sectional view taken along line III-III of the semiconductor laser device shown in FIG. 1. [Figure 4] It is a schematic cross-sectional view taken along line IV-IV of the semiconductor laser device shown in FIG. 1. [Figure 5A] It is a schematic cross-sectional view showing one step in the manufacturing method of the semiconductor laser device according to Embodiment 1. [0000090][0000091]It is a schematic cross-sectional view showing one step in the manufacturing method of the semiconductor laser device according to Embodiment 1. [0000092][0000093]It is a schematic cross-sectional view showing one step in the manufacturing method of the semiconductor laser device according to Embodiment 1. [0000094][0000095]It is a schematic cross-sectional view showing one step in the manufacturing method of the semiconductor laser device according to Embodiment 1. [0000096][0000097]It is a schematic top view showing one step in the manufacturing method of the semiconductor laser device according to Embodiment 1. [0000098] [0000099]It is a schematic cross-sectional view showing one step in the manufacturing method of the semiconductor laser device according to Embodiment 1. [0000100][0000101]It is a schematic top view of the semiconductor laser device according to Embodiment 2 of the present disclosure. [0000102][0000103]It is a schematic top view of the semiconductor laser device according to Embodiment 3 of the present disclosure. [0000104][0000105]It is a schematic top view of the light source device according to Embodiment 4 of the present disclosure. [0000106] [Figure 9A] This graph shows the relationship between waveguide width and the effective refractive index for each transverse mode in the simulation. [Figure 9B] This graph shows the relationship between the waveguide width and the Bragg wavelength at the location where the diffraction grating is placed in the simulation. [Modes for carrying out the invention]

[0009] Hereinafter, embodiments, modifications, and examples for carrying out the invention of this disclosure will be described with reference to the drawings. The semiconductor laser elements described below are intended to embody the technical concept of the invention of this disclosure, and unless otherwise specified, the invention of this disclosure is not limited to the following. In each drawing, components having the same function may be denoted by the same reference numeral. For convenience, in order to explain the key points or to facilitate understanding, components may be shown separately as embodiments, modifications, or examples, but partial substitution or combination of the configurations shown in different embodiments, modifications, and examples is possible. In the embodiments, modifications, and examples described later, descriptions of matters common to those described above will be omitted, and only the differences will be explained. In particular, similar effects and advantages due to similar configurations will not be mentioned sequentially for each embodiment, modification, and example. The size and positional relationships of the components shown in each drawing may be exaggerated to clarify the explanation. In this specification, "orthogonal" or "parallel" includes deviations of ±0.1 degrees, respectively.

[0010] Embodiment 1. Embodiment 1 The semiconductor laser element according to this disclosure comprises a substrate and a semiconductor layer portion disposed on the substrate, the semiconductor layer portion comprising a waveguide including an active layer, wherein the waveguide includes a wide portion comprising a diffraction grating and a narrow portion having a narrower waveguide width than the wide portion and through which light generated in the active layer propagates in transverse multimode, the waveguide includes a first end face including the end face of the narrow portion and a second end face located on the opposite side of the first end face, and the wide portion comprises a first region continuously connected to the narrow portion, the waveguide width widening from the first end face side to the second end face side.

[0011] The semiconductor laser element of Embodiment 1 and its manufacturing method will be described below with reference to Figures 1 to 5F. As shown in Figure 2, the semiconductor laser element 1 according to Embodiment 1 comprises a substrate 2 and a semiconductor layer 3. The semiconductor layer 3 is disposed on the substrate 2. The semiconductor layer 3 includes a waveguide 50 containing an active layer 30. In this specification, the first direction X means the direction in which the laser light oscillates (i.e., the direction of resonance). The second direction Y means the width direction of the waveguide 50. The third direction Z means the stacking direction of the semiconductor layer 3 (i.e., the direction from the substrate 2 toward the semiconductor layer 3). The first direction X, the second direction Y, and the third direction Z are orthogonal to each other. The waveguide 50 extends along the first direction X. As shown in Figure 1, the waveguide 50 includes a wide section 54 and a narrow section 53. Waveguide 50 further includes a first end face 51 and a second end face 52 located opposite the first end face 51. The first end face 51 includes the end face 53a of the narrow portion 53. The wide section 54 is equipped with a diffraction grating 60. The wide section 54 is continuously connected to the narrow section 53. The wide section 54 includes a first region 55 in which the waveguide width widens from the first end face 51 side to the second end face 52 side. The narrow section 53 has a narrower waveguide width than the wide section 54. In the narrow section 53, light generated in the active layer 30 propagates in transverse multimode.

[0012] (substrate) The substrate 2 used in the semiconductor laser element 1 of the present invention is, for example, a semiconductor substrate. The substrate 2 is, for example, a nitride semiconductor substrate such as a GaN substrate. The nitride semiconductor substrate may contain n-type impurities. The elements that constitute the n-type impurities may be, for example, O, Si, or Ge. The substrate 2 can be made of a nitride semiconductor substrate, and its upper surface can be a +c plane (i.e., a (0001) plane). In this embodiment, the c plane is not limited to a plane that strictly coincides with the (0001) plane, but also includes a plane having an off-angle of ±1 degree or less, preferably ±0.03 degrees or less. The semiconductor laser element 1 does not have to have a substrate 2. A non-polar plane (M plane or A plane) or a semi-polar plane (R plane) may be used as the upper surface of the substrate.

[0013] (Semiconductor layer) As shown in Figures 2 to 4, the semiconductor layer 3 includes, in order from the substrate 2 side, a first layer 10, an active layer 30, and a second layer 20. In the semiconductor laser element 1, the first layer 10 and the second layer 20 may be III-V semiconductor layers. Examples of III-V semiconductor layers include In α Al β Ga 1-α-β Examples include nitride semiconductor layers formed with composition N, (0≦α, 0≦β, α+β≦1).

[0014] Examples of n-type impurities used in nitride semiconductor layers include Si or Ge. Examples of p-type impurities include Mg. This allows for the formation of nitride semiconductor layers of various conductivity types.

[0015] (1st layer) The first layer 10 has one or more semiconductor layers containing n-type impurities. The first layer 10 may also have undoped layers that are not intentionally doped with impurities. Starting from the substrate 2 side, the first layer 10 includes a second n-side semiconductor layer 12 with a refractive index of the second refractive index n2, and a first n-side semiconductor layer 11 with a refractive index of the first refractive index n1. The first layer 10 may also include other layers. The first refractive index n1 and the second refractive index n2 are smaller than the refractive index n5 of the active layer 30. The first refractive index n1 and the second refractive index n2 are different from each other. For example, the first refractive index n1 is larger than the second refractive index n2.

[0016] The second n-side semiconductor layer 12 is disposed between the active layer 30 and the substrate 2. The second n-side semiconductor layer 12 may be, for example, a nitride semiconductor layer. Examples of the nitride semiconductor include AlGaN or GaN. The film thickness of the second n-side semiconductor layer 12 may be 0.45 μm or more and 3.0 μm or less. The content of the n-type impurity is 1×10 17 cm -3 or more and 5×10 18 cm -3 or less. In Embodiment 1, the second n-side semiconductor layer 12 can function as, for example, an n-side cladding layer.

[0017] The first n-side semiconductor layer 11 is disposed between the active layer 30 and the second n-side semiconductor layer 12. The first n-side semiconductor layer 11 may be, for example, a nitride semiconductor layer. Examples of the nitride semiconductor include AlGaN, GaN, or InGaN. The film thickness of the first n-side semiconductor layer 11 may be, for example, 0.05 μm or more and 0.5 μm or less. The content of the n-type impurity is 1×10 17 cm -3 or more and 5×10 18 cm -3 or less. In Embodiment 1, the first n-side semiconductor layer 11 can function as, for example, an n-side optical guide layer.

[0018] (Active layer) An active layer 30 is formed on the first n-side semiconductor layer 11. The active layer 30 emits light with a wavelength of, for example, 360 nm to 520 nm. The active layer 30 may have a quantum well structure composed of one or more well layers and multiple barrier layers. The well layers and barrier layers are, for example, GaN, InGaN, AlGaN, or AlInGaN. The well layers are, for example, AlGaN, GaN, or InGaN, and are nitride semiconductors with a smaller band gap than the barrier layers. The active layer 30 may have a multiple quantum well structure or a single quantum well structure. Impurities may be contained in either or both of the well layers and barrier layers.

[0019] (2nd layer) A second layer 20 is formed on the active layer 30, having one or more semiconductor layers containing p-type impurities (hereinafter also referred to as p-side semiconductor layers). The second layer 20 may also have an undoped layer in which impurities are not intentionally doped. The second layer 20 may have a p-side optical guide layer and a p-side cladding layer, or it may have other layers. Specifically, the second layer 20 includes, in order from the substrate 2 side (i.e., from the active layer 30 side), a first p-side semiconductor layer 21 with a refractive index of the third refractive index n3, and a second p-side semiconductor layer 22 with a refractive index of the fourth refractive index n4. The second layer 20 may also include other layers. The third refractive index n3 and the fourth refractive index n4 are smaller than the refractive index n5 of the active layer 30. The third refractive index n3 and the fourth refractive index n4 are different from each other. For example, the third refractive index n3 is greater than the fourth refractive index n4.

[0020] The first p-side semiconductor layer 21 may be, for example, a nitride semiconductor layer. Examples of nitride semiconductors include AlGaN or GaN. The thickness of the first p-side semiconductor layer 21 may be 0.05 μm or more and 0.25 μm or less. The first p-side semiconductor layer 21 may also be an undoped layer, and 1 × 10⁻¹⁶ 16 cm -3 The above 1 x 10 18 cm -3 The following ranges may be used to contain p-type impurities. In Embodiment 1, the first p-side semiconductor layer 21 can function, for example, as a p-side optical guide layer.

[0021] The second p-side semiconductor layer 22 may be, for example, a nitride semiconductor layer. Examples of nitride semiconductors include AlGaN or GaN. It may be a single-layer structure or a multilayer structure in which nitride semiconductor layers with different compositions are stacked. The p-type impurity content is 1 × 10⁻⁶ 17 cm -3 The above 1 x 10 20 cm -3 The following may apply: In Embodiment 1, the second p-side semiconductor layer 22 can function, for example, as a p-side cladding layer.

[0022] (ridge) As shown in Figures 2 to 4, a ridge 70 is provided on the upper surface of the second layer 20 of the semiconductor layer 3. Figure 2 is a cross-section taken along line II-II in Figure 1, and is a cross-section of the narrow portion 53. Figure 3 is a cross-section taken along line III-III in Figure 1, and is a cross-section of the wide portion 54. Figure 4 is a cross-section taken along line IV-IV in Figure 1. The ridge 70 is provided, for example, on a part of the upper surface of the second p-side semiconductor layer 22. As shown in Figure 4, the ridge 70 extends in the first direction X between the first surface 1a and the second surface 1b of the semiconductor laser element 1. In Figure 4, to facilitate understanding of the drawing, the portion of the second p-side semiconductor layer 22 corresponding to the ridge 70 is demarcated with a dotted line.

[0023] Below the ridge 70, a waveguide 50 is formed, which includes an active layer 30. The waveguide 50 includes a core and a cladding. The core includes the active layer 30 and is the portion through which light emitted from the active layer 30 primarily propagates. The core may include the active layer 30 and at least a portion of the semiconductor layer 3 located around it.

[0024] The cross-sectional shape of the ridge 70 in the second direction Y is, as shown in Figures 2 and 3, a trapezoidal shape in which the width in the second direction Y narrows as it moves away from the substrate 2. Alternatively, the cross-sectional shape of the ridge 70 in the second direction Y may be a rectangular shape in which the width in the second direction Y is constant along the third direction Z. The shape of the ridge 70 in a top view, particularly the width in the second direction Y, is determined appropriately so that the shape of the waveguide 50, which will be described later, can be obtained.

[0025] Although this embodiment uses a ridge-type waveguide for explanation, a gain-type waveguide may also be used.

[0026] (Waveguide) The detailed shape of the waveguide 50 will be described below with reference to Figures 1 to 3. Figure 1 is a schematic top view of the semiconductor laser element 1, with the waveguide 50 and diffraction grating 60 depicted as transparent using dashed lines. The dashed lines shown in Figures 2 and 3 represent an example of the area that includes the waveguide 50.

[0027] As shown in Figure 1, the waveguide 50 extends in a first direction X. The waveguide 50 includes a first end face 51 and a second end face 52 located opposite the first end face 51 in the first direction X. The waveguide 50 includes a narrow section 53 and a wide section 54 that is wider than the narrow section 53.

[0028] One end face 53a of the narrow portion 53 is included in the first end face 51. In Embodiment 1, one end face 53a of the narrow portion 53 coincides with the first end face 51. In the narrow portion 53, light generated in the active layer 30 propagates in transverse multimode. The width of the narrow portion 53 and the difference in refractive index between the core and cladding of the waveguide determine the number of transverse modes of the semiconductor laser element 1. In other words, in the narrow portion 53, the normalized frequency V satisfies the following equation 1 so that it becomes a transverse multimode waveguide.

[0029] (Formula 1) TIFF2026123125000002.tif914 (N is an integer greater than or equal to 1)

[0030] In Equation 1, N is the mode order of the transverse mode.

[0031] As shown in Equation 1, the semiconductor laser element of this embodiment has a normalized frequency V of π / 2 or more. The normalized frequency V of the narrow portion 53 is preferably 9π / 2 or more and 100π / 2 or less, more preferably 9π / 2 or more and 50π / 2 or less. This makes it possible to obtain a desired number of transverse modes.

[0032] The width of the narrow portion 53 is, for example, 15 μm to 90 μm. This allows for the creation of a semiconductor laser element with a desired number of transverse modes. The width of the narrow portion 53 is constant. Constant means that the width varies within a range of 0% to 10%.

[0033] By using a waveguide with transverse multimode oscillation in the narrow section 53, the following advantages can be obtained. The first advantage is the reduction of sudden death at the light emission surface. This is because the near-field pattern of the output beam can reduce localized concentration of light density compared to the case of a transverse single mode. The second advantage is the reduction of output fluctuations. This is because a longitudinal mode exists for each transverse mode, and when the semiconductor laser element as a whole oscillates in longitudinal multimode, the fluctuations in the total output are small. In the case of a semiconductor laser with longitudinal single mode, if competition occurs with adjacent modes at the free spectral spacing, the output may fluctuate depending on the oscillating longitudinal mode.

[0034] The wide portion 54 is continuously connected to the narrow portion 53. The wide portion 54 is located on the second end face 52 side of the narrow portion 53. One end face 54a of the wide portion 54 is included in the second end face 52. In Embodiment 1, one end face 54a of the wide portion 54 coincides with the second end face 52. The wide portion 54 includes a first region 55 whose width widens along a first direction X from the first end face 51 toward the second end face 52. In this embodiment, the wide portion 54 and the first region 55 are in the same area. Therefore, one end face of the first region 55 is the second end face 52.

[0035] The width of the wide portion 54, i.e., the width of the first region 55, changes (expands) in such a way that the number of transverse multimodes determined in the narrow portion 53 does not increase or decrease easily with propagation. The width of the first region 55 changes in a range greater than 15 μm and less than or equal to 360 μm. The width of the first region 55 expands at a constant rate along the first direction X from the first end face 51 to the second end face 52. That is, as shown by the dashed line in Figure 1, the contour shape of the first region 55 in a top view may be a straight line. Alternatively, the contour shape of the first region 55 in a top view may be a curve, as long as the shape does not increase or decrease easily with transverse modes.

[0036] The width change (degree of expansion) of the first region 55 is such that, for example, the width y2 of the end of the first region 55 on the second end face 52 side is between 2 and 4 times the width y1 of the end of the first region 55 on the first end face 51 side. This makes it less likely for the heat generated by the application of current to be concentrated on the second end face 52 side, thereby reducing the thermal damage suffered by the semiconductor laser element 1.

[0037] As described above, the ridge 70 has a shape that overlaps with the waveguide 50 when viewed from above. The ridge 70 in Embodiment 1 is formed in a shape that yields a waveguide 50 having the above-described shape.

[0038] (Diffraction grating) As shown in Figure 1, the diffraction grating 60 is provided on the wide portion 54 in a top view. In the semiconductor laser element of Embodiment 1, the diffraction grating is provided only on the wide portion 54. This makes it possible to select the wavelength in a region where the difference in effective refractive index for each transverse mode is small, that is, in a region where the variation in effective refractive index for each transverse mode is small. Therefore, a transverse multimode semiconductor laser element with small variation in oscillation wavelength can be obtained. This point will be explained using the results of a simulation.

[0039] First, let's explain the simulation conditions. For simplicity, the simulation assumed a symmetric three-layer flat-plate waveguide, and the eigenvalue equations were solved. The simulation conditions were: core refractive index n コア= 2.5035, and the refractive index of the cladding n クラッド We set it to =2.4974. Note that the parameter has been set to 5 significant figures, but this is to improve the accuracy of the simulation and does not mean that the same level of accuracy is required in actual manufacturing.

[0040] Figure 9A shows the relationship between waveguide width and the effective refractive index for each transverse mode. Figure 9A shows only the transverse modes that can oscillate when the waveguide width is 15 μm. In other words, for the semiconductor laser element of this embodiment, it shows the transverse modes that can oscillate when the waveguide width of the narrow section 53 is 15 μm. In this simulation, modes from the fundamental mode (0th order mode) to the 12th order higher mode are plotted. In Figure 9A, the effective refractive index of the fundamental mode is represented by the leftmost solid line, and the effective refractive index of the 12th order higher mode is represented by the rightmost solid line. The effective refractive index is a value obtained using the normalized frequency and normalized propagation constant obtained by solving the eigenvalue equation for each waveguide width.

[0041] Next, based on the results in Figure 9A, the Bragg wavelength was simulated when a diffraction grating 60 is provided in the waveguide. Figure 9B shows the relationship between the waveguide width and the Bragg wavelength at the location where the diffraction grating 60 is provided. In Figure 9B, the Bragg wavelength of the fundamental mode is represented by the leftmost solid line, and the Bragg wavelength of the 12th higher-order mode is represented by the rightmost solid line. The Bragg wavelength is given by the Bragg wavelength (λ). B ) = effective refractive index (n eff The value was calculated using the formula: () × pitch (or period, P) of the diffraction grating × 2. However, the period of diffraction grating 60 was assumed to be 80.886 nm. This value is based on the assumption that the fundamental mode converges to 405 nm when the waveguide width is sufficiently wide.

[0042] The simulation results are compared at waveguide widths of 15 μm, 30 μm, and 60 μm. In Figures 9A and 9B, these locations are shown with dashed lines for easier reference. First, in Figure 9A, focusing on the effective refractive index at these dashed line locations, it can be seen that the difference in effective refractive index for each transverse mode decreases as the waveguide width increases. This is because the amount of seepage into the cladding differs for each transverse mode, and the amount of seepage into the cladding decreases as the waveguide width increases. Next, in Figure 9B, similar to Figure 9A, focusing on the Bragg wavelength at these dashed line locations, it can be seen that the difference in Bragg wavelength for each transverse mode decreases as the waveguide width increases. This is because the difference in effective refractive index, i.e., the variation in effective refractive index, decreases as the waveguide width increases. For example, at waveguide widths of 15 μm, 30 μm, and 60 μm, the difference between the Bragg wavelength of the fundamental mode and the Bragg wavelength of the 12th higher-order mode—that is, the difference between the longest and shortest wavelengths of each Bragg wavelength—was 0.874 nm, 0.235 nm, and 0.063 nm, respectively.

[0043] As mentioned above, this simulation assumes a waveguide width of 15 μm for the narrow section 53. Therefore, in Figures 9A and 9B, the results for a waveguide width of 15 μm represent the state where the waveguide width is not widened. Furthermore, when the waveguide width is greater than 15 μm, for example, the results for 30 μm and 60 μm represent the state where the waveguide width is widened, that is, the state corresponding to the wide section 54 is shown. Therefore, from the simulation results, the semiconductor laser element according to Embodiment 1, by providing a diffraction grating 60 in the wide section 54 which has a larger waveguide width than the narrow section 53, enables wavelength selection in a region where the variation in effective refractive index is smaller than in the narrow section 53, and a transverse multimode semiconductor laser element 1 with small variation in Bragg wavelength, i.e., oscillation wavelength, can be obtained.

[0044] The diffraction grating 60 is provided, for example, in the wide portion 54, in a portion where the oscillation wavelength for each transverse mode falls within a wavelength range of 0.01 nm to 0.5 nm, preferably 0.01 nm to 0.3 nm, and more preferably 0.01 nm to 0.1 nm.

[0045] The diffraction grating 60 has, for example, different refractive indices and is provided between two adjacent semiconductor layers. The diffraction grating 60 includes, for example, one or more first protrusions provided on the surface of one semiconductor layer and one or more second protrusions provided on the surface of the other semiconductor layer. There may be multiple first and second protrusions. The first and second protrusions are arranged periodically in the direction of light propagation. The first and second protrusions may be arranged alternately with each other.

[0046] The diffraction grating 60 of this embodiment is provided between a first n-side semiconductor layer 11 and a second n-side semiconductor layer 12, for example, as shown in Figure 4. The diffraction grating 60 includes one or more second protrusions 62 provided on the surface of the first n-side semiconductor layer 11 and one or more first protrusions 61 provided on the surface of the second n-side semiconductor layer 12. The second protrusions 62 are provided on the surface of the first n-side semiconductor layer 11 that is on the second n-side semiconductor layer 12 side. That is, the second protrusions 62 are provided on the lower surface of the first n-side semiconductor layer 11. The first protrusions 61 are provided on the surface of the second n-side semiconductor layer 12 that is on the first n-side semiconductor layer 11 side. That is, the first protrusions 61 are provided on the upper surface of the second n-side semiconductor layer 12. The first protrusions 61 are formed alternately and periodically with, for example, first recesses 63 provided on the upper surface of the second n-side semiconductor layer 12. Alternatively, it may be assumed that the second recess 64 and the second protrusion 62 are formed alternately and periodically in the lower portion of the first n-side semiconductor layer 11, and the first protrusion 61 is formed in the upper portion of the second n-side semiconductor layer 12.

[0047] As shown in Figures 1 and 4, the first protrusion 61 and the second protrusion 62 are arranged periodically in the first direction X. The first protrusion 61 and the second protrusion 62 are each arranged parallel to the second end face 52. In other words, as shown in Figure 1, the direction in which each first protrusion 61 extends and the direction in which each second protrusion 62 extends are both parallel to the second direction Y.

[0048] The diffraction grating 60 may be provided not only on the waveguide 50, but also, as shown in Figure 1, across the entire second direction Y of the semiconductor layer 3 in a top view. Specifically, in the semiconductor laser element 1, the diffraction grating 60 may be provided on the first n-side semiconductor layer 11 and the second n-side semiconductor layer 12 located on both sides of the waveguide 50 in the second direction Y. The width y3 of the diffraction grating 60 that overlaps with the wide portion 54 is, for example, 0.1 times or more and 0.9 times or less the width of the diffraction grating 60 in the second direction Y. The width y4 of the region that does not overlap with the wide portion is, for example, 0.1 times or more and 0.9 times or less the width of the diffraction grating 60 in the second direction Y. Note that the width y4 is the sum of the width of the semiconductor layer 3 located on one side of the waveguide 50 in the second direction Y and the width of the semiconductor layer 3 located on the other side of the waveguide 50 in the second direction Y.

[0049] The diffraction grating 60 is positioned in the wide section 54 in a portion of the wide section 54 whose width is greater than or equal to a predetermined value. For example, the diffraction grating 60 is provided in the wide section 54 in a portion having a waveguide width of 2 to 4 times the waveguide width of the narrow section 53. This further reduces the variation in oscillation wavelength for each transverse mode. Also, when focusing on one of the multiple transverse modes, the range of oscillation wavelengths selected by the diffraction grating becomes narrower. For example, it is preferable that there is one longitudinal mode corresponding to one transverse mode. For example, the diffraction grating 60 is provided in the wide section 54 in a portion where the waveguide width is 30 μm to 360 μm, preferably 30 μm to 100 μm, and more preferably 30 μm to 60 μm. This makes the waveguide width of the wide section 54 sufficiently wider than the waveguide width of the narrow section 53, thereby reducing the variation in oscillation wavelength for each transverse mode.

[0050] Furthermore, a transverse single-mode distributed feedback (DFB) laser element, which typically has a uniform diffraction grating along the entire length of the waveguide, can oscillate at the center of the reflection band of the diffraction grating, i.e., the Bragg wavelength, by providing a λ / 4 phase shift region. In the semiconductor laser element 1 of Embodiment 1, as shown in Figure 4, the distance L between the diffraction grating 60 and the first end face 51 on which the reflective coating 40 is formed can be considered to have a similar effect to a λ / 4 phase shift. This makes it easier to control the oscillation wavelength and reduces the variation in the oscillation wavelength of the laser light from the semiconductor laser element 1.

[0051] Therefore, in the semiconductor laser element 1 of Embodiment 1, the first end face 51 and the diffraction grating 60 are separated by a distance L that satisfies, for example, the following equation 2. That is, the diffraction grating 60 is provided on the second end face 52 side from a position separated by a distance L from the first end face 51.

[0052] (Formula 2) L = (m + 1 / 4) × λ0 / n eff

[0053] In equation 2, n eff λ is the effective refractive index of each transverse mode, m (m≧0) is an integer determined for each effective refractive index, and λ0 is the oscillation wavelength of each transverse mode in vacuum. In Equation 2, the phase difference arising in the first term containing m is an integer multiple of the wavelength and can therefore be ignored. Thus, the net phase difference arising in Equation 2 is 1 / 4 × λ0 / n eff This has the same effect as a simple λ / 4 phase shift. In this embodiment, m can take values ​​of, for example, several thousand. However, if this length L cannot be measured accurately, it is acceptable to consider that equation 2 is satisfied if an integer is included in the range of m estimated when considering measurement errors.

[0054] The distance L may include as an allowable error a deviation of approximately the width x1 of the first protrusion 61 of the diffraction grating 60 in the first direction X (or the width x2 of the second protrusion 62 in the first direction X). The width x1 of the first protrusion 61 (or the width x2 of the second protrusion 62) depends, for example, on the height z1 of the first protrusion 61 in the third direction Z (or the height z2 of the second protrusion 62 in the third direction), the distance d1 of the first protrusion 61 to the active layer 30 in the third direction Z (or the distance d2 of the second protrusion 62 to the active layer 30 in the third direction), etc.

[0055] The shapes of the first protrusion 61, the second protrusion 62, and the first recess 63 (or second recess 64) are not particularly limited. For example, the cross section perpendicular to the second direction Y may be sawtooth, sinusoidal, rectangular, trapezoidal, inverted trapezoidal, etc., and is preferably rectangular, trapezoidal, or inverted trapezoidal.

[0056] The pitch P of the diffraction grating 60 is, for example, 20 nm to 500 nm, preferably 30 nm to 250 nm, and more preferably 40 nm to 140 nm. In the first direction X, the width x1 of the first protrusion and the width x2 of the second protrusion 62 are preferably the same, but they may be different.

[0057] In the third direction Z, the height z1 of the first protrusion 61 and the height z2 of the second protrusion 62 are, for example, 50 nm to 300 nm, preferably 50 nm to 150 nm. The heights z1 of the first protrusion 61 and z2 of the second protrusion 62 may be the same or different. By using this size and depth, the desired coupling coefficient can be obtained, and the wavelength selectivity for each transverse mode is improved.

[0058] (Semiconductor laser element) The semiconductor laser element 1 according to Embodiment 1 having the above configuration functions as a DFB laser element. As shown in Figure 1, the semiconductor laser element 1 has a first surface 1a and a second surface 1b located opposite to the first surface 1a in the first direction X. The first surface 1a and the second surface 1b extend on a plane that extends in the second direction Y and the third direction Z. The first surface 1a has a reflective coating (HR coating) 40 formed on it. The second surface 1b has an anti-reflective coating (AR coating) 41 formed on it. The semiconductor laser element 1 is equipped with a diffraction grating 60 in the wide portion 54 of the waveguide 50, forming an optical resonator with the first direction X as the resonance direction (waveguide direction of light). The second surface 1b is a light emission surface that mainly functions to emit light to the outside of the semiconductor laser element 1.

[0059] (electrode) As shown in Figures 2, 3, and 4, the semiconductor laser element 1 comprises a first electrode 5 and a second electrode 6.

[0060] The first electrode 5 is a negative electrode. The first electrode 5 is provided in an electrically connected state to the second n-side semiconductor layer 12, ensuring ohmic contact. For example, the first electrode 5 is provided in contact with the second n-side semiconductor layer 12. Alternatively, the first electrode 5 may be placed on the underside of the substrate 2, for example, if the substrate 2 is conductive and ohmic contact can be ensured. The first electrode 5 is, for example, a multilayer structure of metal layers. Examples of materials for the first electrode 5 include single-layer or multilayer films of metals or alloys such as Ni, Rh, Cr, Au, W, Pt, Ti, Al, and conductive oxides containing at least one selected from Zn, In, and Sn. Examples of conductive oxides include ITO (Indium Ti Oxide), IZO (Indium Zinc Oxide), and GZO (Gallium-doped Zinc Oxide). For example, the first electrode 5 is a multilayer structure of Ti and Au.

[0061] The second electrode 6 is the positive electrode. The second electrode 6 is provided in contact with the upper surface of the ridge 70. The second electrode 6 is, for example, a multilayer structure of metal layers. The material of the second electrode 6 can be selected from the same materials as the first electrode 5. The second electrode 6 is, for example, a multilayer structure of Ni and Au. The second electrode 6 may be provided over a wider area than the upper surface of the ridge 70. However, in this case, as shown in Figures 2 and 3, an insulating member 4 is provided between the upper surface of the second layer 20, excluding the upper surface of the ridge 70, and the second electrode 6.

[0062] In the semiconductor laser element 1 configured as described above, more than 90% of the total output of the light emitted from the second end face 52 falls within a wavelength range of, for example, 0.01 nm to 0.5 nm. That is, multiple oscillation wavelengths of the light fall within a range of, for example, 0.01 nm to 0.5 nm. This means that the variation in the oscillation wavelength of the laser light for each transverse mode, which is wavelength-selected by the diffraction grating 60, is small. This can be determined by analyzing the power of the output light and its wavelength dispersion.

[0063] Furthermore, the semiconductor laser element 1 configured as described above emits light M from the second end face 52. 2 The factor is, for example, between 5 and 50. This allows us to obtain a desired number of transverse modes. For example, we can obtain a number of transverse modes between 10 and 100, preferably between 10 and 50. M 2 The factor is a comparison between the actual beam shape and the ideal Gaussian beam shape. 2 The factor is defined by the following equation 3, using the beam waist ω0 of the semiconductor laser element 1, the divergence angle θ of the semiconductor laser element 1, and the oscillation wavelength λ of the semiconductor laser element 1.

[0064] (Formula 3) TIFF2026123125000003.tif922

[0065] In the semiconductor laser element 1 configured as described above, the waveguide 50 includes a wide section 54 that is wider than the narrow section 53, and a diffraction grating 60 is provided in the wide section 54. As a result, the transverse multimode light propagating through the narrow section 53 is wavelength-selected by the diffraction grating 60 in the wide section, where the variation in the effective refractive index of each transverse mode is smaller than in the narrow section 53. Therefore, the oscillation wavelength of each transverse mode can be contained within a predetermined wavelength width, and the variation in the oscillation wavelength of each transverse mode can be reduced in the semiconductor laser element.

[0066] In Embodiment 1, the first n-side semiconductor layer 11 was described as an n-side optical guide layer, and the second n-side semiconductor layer 12 was described as an n-side cladding layer. However, the disclosure is not limited thereto. For example, another semiconductor layer may be provided between the second n-side semiconductor layer 12 and the substrate 2 as an n-side cladding layer. In this case, both the first n-side semiconductor layer 11 and the second n-side semiconductor layer 12 may be n-side optical guide layers. Alternatively, a semiconductor layer may be provided between the active layer 30 and the first n-side semiconductor layer 11 as an n-side optical guide layer. In this case, both the first n-side semiconductor layer 11 and the second n-side semiconductor layer 12 may be n-side cladding layers. Or, the first n-side semiconductor layer 11 may be an n-side optical guide layer, and the second n-side semiconductor layer 12 may be an n-side cladding layer. Therefore, the diffraction grating 60 may be provided at any of the following positions: between the n-side optical guide layers, between the n-side optical guide layers and the n-side cladding layers, or between the n-side cladding layers. Furthermore, the diffraction grating 60 may be provided on the p-side semiconductor layer side. For example, other semiconductor layers may be provided between the active layer 30 and the first p-side semiconductor layer 21, and / or between the second p-side semiconductor layer 22 and the second electrode 6. Therefore, the diffraction grating 60 may be provided at any of the following positions: between p-side optical guide layers, between p-side optical guide layers and p-side cladding layers, or between p-side cladding layers.

[0067] 2. Manufacturing method The method for manufacturing the semiconductor laser element 1 according to this embodiment is as follows: (i) The process of preparing the substrate, (ii) A step of forming a semiconductor layer and a diffraction grating, (iii) The process of forming a ridge, (iv) Steps to form electrodes, This includes the semiconductor layer. Each semiconductor layer in the semiconductor layer portion can be formed by any method known in the art, such as MOCVD (metal-organic vapor deposition), HVPE (halide vapor deposition), MBE (molecular beam emission), or sputtering.

[0068] (i) Process of preparing the substrate First, prepare a substrate 2 made of, for example, GaN.

[0069] (ii) Process of forming the semiconductor layer and the diffraction grating Next, as shown in Figure 5A, a second n-side semiconductor layer 12 is formed on the substrate 2. Alternatively, a base layer may be provided on the substrate 2 before forming the second n-side semiconductor layer 12.

[0070] As a method for forming the diffraction grating 60, first, the second n-side semiconductor layer 12 is formed, and then, as shown in Figure 5B, a mask pattern 80 is formed. Methods for forming the mask pattern 80 include, for example, photolithography and etching processes using methods known in the field, such as the double resist method, contact mask exposure method, electron beam lithography method, and phase shift method. Next, the mask pattern 80 is used as a mask to etch and form the first recess 63 and the first protrusion 61. After that, as shown in Figure 5C, the mask pattern 80 is removed, and the first recess 63 of the second n-side semiconductor layer 12 can be filled with the second protrusion 62 of the first n-side semiconductor layer 11 to form the diffraction grating.

[0071] The mask pattern 80 in this case can be formed using various resists, oxides and nitrides such as Al2O3, ZrO2, SiO2, TiO2, Ta2O5, AlN, and SiN, or single-layer or multi-layer films of metals such as nickel and chromium. The film thickness is preferably, for example, 10 nm to 500 nm. This makes it possible to form the heights of the first protrusion 61 and the second protrusion 62 to a desired height.

[0072] In particular, when patterning using a low refractive index material, such as SiO2, TiO2, ZrO2, Al2O3, SiN, AlN, etc., as the mask pattern 80, the first n-side semiconductor layer 11 may be grown without removing the mask pattern 80. As a result, a material with a lower refractive index than the nitride semiconductor is placed on the upper surface of the first protrusion 61, and this low refractive index material can further improve the effect of the diffraction grating 60.

[0073] Furthermore, when etching the semiconductor layer using the mask pattern 80 to form the first convex portion 61 and the first concave portion 63, the etching is performed, for example, by dry etching. For example, when using dry etching, it is preferable to etch at a pressure in the range of 0.05 Pa to 10 Pa (a constant pressure or a pressure that is changed as appropriate). This makes it possible to efficiently etch to the desired depth.

[0074] After forming the first n-side semiconductor layer 11, as shown in Figure 5D, an active layer 30 and a second layer 20 are formed sequentially on the first n-side semiconductor layer 11 to prepare the semiconductor layer portion 3. The second layer 20 may be formed by first p-side semiconductor layer 21 and second p-side semiconductor layer 22 in order from the substrate 2 side. If the active layer 30 has a multiple quantum well structure, the barrier layer and the well layer are formed alternately in the desired number of layers from the substrate 2 side to form the active layer 30. In this case, the process of forming the active layer 30 is completed in the process of forming the barrier layer.

[0075] (iii) process of forming a ridge As shown in Figure 5E, the ridge 70 is formed on the surface of the semiconductor layer 3 after the semiconductor layer 3 has been formed. The ridge 70 is provided to form a narrow portion and a wide portion that is wider than the narrow portion in terms of waveguide width. For example, a protective film made of Si oxide (mainly SiO2) is formed on almost the entire surface of the second p-side semiconductor layer 22 (p-side cladding layer) using a CVD apparatus. Then, a mask of a predetermined shape is formed on the protective film, and a striped and tapered protective film 81 is formed using photolithography technology with a reactive ion etching (RIE) apparatus or the like. The width of the tapered portion of the protective film 81 is made larger than the width of the striped portion. Using this protective film 81 as a mask, a ridge 70 can be formed, for example, by etching the second p-side semiconductor layer 22. The ridge 70 is usually etched from the second p-side semiconductor layer 22 and preferably formed on the second layer 20 side of the active layer 30. For example, the ridge 70 may be formed by etching up to a certain point in the second p-side semiconductor layer 22, or by etching from the second p-side semiconductor layer 22 to a certain point in the first p-side semiconductor layer 21.

[0076] (iv) Process of forming electrodes As shown in Figure 5F, the second electrode 6 is formed on the upper surface of the ridge 70, and the first electrode 5 is formed on the lower surface of the substrate 2. The second electrode 6 is formed in contact with and covering the upper surface of the ridge 70. To prevent the second electrode 6 from being formed in contact with anything other than the upper surface of the ridge 70, a mask is placed on the upper surface of the semiconductor layer 3, specifically the upper surface of the ridge 70, and an insulating member 4 is placed on the upper surface of the semiconductor layer 3. The insulating member 4 is placed, for example, by sputtering. Subsequently, the mask and the insulating member 4 placed on the mask are removed, for example, by etching. The second electrode 6 is then formed on the exposed upper surface of the ridge 70, for example, by sputtering.

[0077] The first electrode 5 is positioned to be electrically connected to the second p-side semiconductor layer 22. If the substrate 2 is conductive, the first electrode 5 can be formed on the underside of the substrate 2. The first electrode 5 is formed, for example, by sputtering. The first electrode 5 and the second electrode 6 can be formed using known methods other than sputtering. For example, the first electrode 5 and the second electrode 6 can be formed by a lift-off process or etching process using a resist. A translucent electrode may be formed between the first electrode 5 and the substrate 2. Alternatively, the first electrode may be formed directly on the first n-side semiconductor layer 11 or the second n-side semiconductor layer 12.

[0078] After the electrode formation process, a reflective coating may be formed on the first surface 1a and a non-reflective coating on the second surface 1b. The reflective coating and non-reflective coating can be formed by vapor deposition, sputtering, etc. The reflective coating and non-reflective coating may be formed at any stage of the semiconductor layer and diffraction grating formation process.

[0079] 3. Embodiment 2 The semiconductor laser element 101 according to Embodiment 2 differs from the semiconductor laser element 1 according to Embodiment 1 in that, as shown in Figure 6, the wide portion has a second region 56 with a constant width. Here, "constant" includes, for example, a variation in width within a range of 0% to 10%. The second region 56 is connected to the first region 55 in a continuous manner. The second region 56 is located, for example, between the first region 55 and the second end face 52. One end face 56a of the second region 56 is included, for example, in the second end face 52. The diffraction grating 60 is provided, for example, in the second region 56. The diffraction grating 60 may span both the first region 55 and the second region 56.

[0080] By providing the diffraction grating 60 in the second region 56 in this manner, the direction of light propagation D1 in the diffraction grating 60 becomes perpendicular to the diffraction grating 60. Specifically, the direction of light propagation D1 in the diffraction grating 60 is perpendicular to the direction in which each first protrusion 61 extends and the direction in which each second protrusion 62 extends, i.e., the second direction Y. As a result, the wavefront of the light propagating through the diffraction grating 60 and the diffraction grating 60 become parallel, reducing the loss of propagating light. In addition, the variation in the oscillation wavelength of the semiconductor laser element 1 can be reduced.

[0081] 4. Embodiment 3 The semiconductor laser element 201 according to Embodiment 3 differs from the semiconductor laser element 1 according to Embodiment 1 in that, as shown in Figure 7, the diffraction grating 260 is arranged in a convex curve from the first end face 51 to the second end face 52 when viewed from above. Each first protrusion 261 and each second protrusion 262 are arranged in a convex curve from the first end face 51 to the second end face 52 when viewed from above. The tangents L1 on the inner circumference of each first protrusion 261 and L2 on the inner circumference of each second protrusion 262 are, for example, parallel to the wavefront of propagating light.

[0082] Because the diffraction grating 260 is arranged in a convex curve from the first end face 51 to the second end face 52, the direction of light propagation D2 in the diffraction grating 260 can be made perpendicular to the diffraction grating 260. As a result, the wavefront of the light propagating through the diffraction grating 260 and the diffraction grating 260 become parallel, reducing the loss of propagating light. In addition, the variation in the oscillation wavelength of the semiconductor laser element 1 can be reduced.

[0083] Furthermore, the curved diffraction grating 260 described above is also applicable to the semiconductor laser element 101 according to Embodiment 2 when the diffraction grating is provided in the first region 55.

[0084] 5. Embodiment 4 As shown in Figure 8, Embodiment 4 relates to a light source device 400 that includes any of the semiconductor laser elements 1, 101, and 201 according to Embodiments 1 to 3 described above. The light source device 400 can be used in Wavelength Beam Combining (WBC). This makes it possible to improve the output of the light source device.

[0085] The light source device 400 comprises a plurality of light source units 91 and a diffraction grating 93 for wave multiplexing. Each of the plurality of light source units 91 comprises a semiconductor laser element 1 (or 101, or 201) according to any of Embodiments 1 to 3 and a collimating lens 92. The oscillation wavelengths of the semiconductor laser element 1 of each light source unit 91 are λ1, λ2, ..., λ qThese are all different. q is an integer used to distinguish between multiple light source units 91. The semiconductor laser element 1 is a longitudinal multimode semiconductor laser, and the oscillation wavelength λ is output from each light source unit 91. q This includes multiple oscillation wavelengths. However, all oscillation wavelengths λ q In this configuration, the number of longitudinal modes does not need to match. The collimating lens 92 is positioned where light emitted from the semiconductor laser element 1 (or 101, or 201) is incident. Note that the light source unit 91 does not need to consist of only one semiconductor laser element 1 (or 101, 201) and one collimating lens 92; it may have multiple such sets. This allows the oscillation wavelength λ of the light source unit 91 to be determined. q The output can be increased per unit.

[0086] The multiplexing diffraction grating 93 combines light emitted from multiple light sources 91. The multiplexing diffraction grating 93 includes, for example, periodically arranged grooves and protrusions. Each light source 91 is arranged such that the relationship between the incident angle α at which light emitted from the collimating lens 92 enters the multiplexing diffraction grating 93 and the diffraction angle β of the light diffracted by the multiplexing diffraction grating 93 satisfies the following equation 4.

[0087] (Formula 4) TIFF2026123125000004.tif532

[0088] In Equation 4, G is the number of grooves in the diffraction grating of the multiplexing grating 93 (g / mm), l is the order, and λ is the oscillation wavelength of the semiconductor laser element 1 (nm).

[0089] Oscillation wavelength λ output from each light source unit 91 qThe light source unit 91 contains multiple oscillation wavelengths, and the diffraction angle β corresponding to each oscillation wavelength is different. However, the semiconductor laser element 1 included in the light source unit 91 has a diffraction grating on its wide portion, resulting in small variations in oscillation wavelengths. For example, the oscillation wavelength for each transverse mode is within a wavelength range of 0.01 nm to 0.5 nm. This reduces the difference between the oscillation wavelength for each transverse mode and the corresponding diffraction angle β. Therefore, the light emitted from each light source unit 91 can be combined with the diffraction grating 93 to achieve approximately the same diffraction angle. As a result, the light emitted from the light source device 400 has high optical output. The light emitted from the light source device 400 configured as described above is introduced into, for example, a multimode fiber. The core diameter of the multimode fiber is greater than the width of the second end face (light emission surface) 52 of each semiconductor laser element 1. The core diameter of the multimode fiber is, for example, 90 μm or more and 400 μm or less.

[0090] 6. Variations The semiconductor laser elements 1, 101, and 201 according to Embodiments 1 to 4 were DFB type semiconductor laser elements, but they may also be distributed reflection (DBR: Distributed Bragg Reflector) type semiconductor laser elements. In the case of a DBR type semiconductor laser element, electrodes are not included directly above or below the position where the diffraction grating 60 is provided. For example, the narrow portion includes the active layer, while the wide portion does not include the active layer.

[0091] 7. Other configurations Furthermore, for example, this disclosure can take the following form. (Section 1) circuit board and A waveguide including an active layer is provided, and a semiconductor layer portion is disposed on the substrate, Equipped with, The waveguide is, A wide section equipped with a diffraction grating, A narrow section having a waveguide width narrower than the wide section, in which light generated in the active layer propagates in transverse multimode, Includes, The waveguide comprises a first end face including the end face of the narrow portion, and a second end face located on the opposite side of the first end face. The aforementioned wide portion is, A first region is continuously connected to the aforementioned narrow portion, and the waveguide width widens from the first end face side to the second end face side, A semiconductor laser element equipped with the following features. (Section 2) The waveguide further includes a second region, The second region is connected to the first region in a continuous manner. The waveguide width in the second region is constant. The second region is the semiconductor laser element according to item 1, including the diffraction grating. (Section 3) The semiconductor layer includes a first semiconductor layer having a first refractive index and a second semiconductor layer having a second refractive index different from the first refractive index. The semiconductor laser element according to claim 1 or 2, wherein in the diffraction grating, one or more first protrusions provided on the surface of the first semiconductor layer and one or more second protrusions provided on the surface of the second semiconductor layer are periodically arranged in the direction of light propagation in the diffraction grating. (Section 4) The semiconductor laser element according to claim 3, wherein the first semiconductor layer is disposed between the active layer and the second semiconductor layer. (Section 5) The semiconductor laser element according to claim 3 or 4, wherein each of the first and second protrusions is arranged parallel to the second end face. (Section 6) The semiconductor laser element according to claim 3 or 4, wherein each of the first and second protrusions is arranged to curve convexly from the first end face side to the second end face side. (Section 7) The semiconductor laser element according to item 6, wherein the tangents to the inner circumference of each of the first protrusions and the tangents to the inner circumference of each of the second protrusions are parallel to the wavefront of the propagating light. (Section 8) A semiconductor laser element according to any one of items 1 to 7, wherein 90% or more of the total output of light emitted from the second end face falls within a wavelength range of 0.01 nm to 0.5 nm. (Section 9) The semiconductor laser element according to any one of claims 1 to 8, wherein the waveguide width of the portion where the diffraction grating is provided is 2 to 4 times the waveguide width in the narrow portion. (Section 10) The semiconductor laser element according to any one of items 1 to 9, wherein the waveguide width in the narrow portion is 15 μm or more and 90 μm or less. (Section 11) The semiconductor laser element according to any one of items 1 to 10, wherein the waveguide width of the portion where the diffraction grating is provided is 30 μm or more and 360 μm or less. (Section 12) The distance from the first end face to the diffraction grating is an integer m and the effective refractive index n of each transverse mode. eff And, using the wavelength λ0 of each transverse mode in a vacuum, (m+1 / 4)×λ0 / n eff A semiconductor laser element described in any one of items 1 to 11, as expressed as follows. (Section 13) The M of light emitted from the second end face 2 The factor is a semiconductor laser element described in any one of items 1 to 12, where the factor is between 5 and 50. (Section 14) Multiple light sources, A diffraction grating for wave multiplexing is provided, Each of the aforementioned plurality of light sources is A semiconductor laser element described in any one of items 1 to 13, The system comprises a collimating lens provided at the position into which light emitted from the semiconductor laser element is incident, The diffraction grating for wave multiplexing is a light source device that combines light emitted from the plurality of light source units.

[0092] While embodiments and modifications of this disclosure have been described above, the disclosure may be modified in detail, and changes in the combination and order of elements in the embodiments and modifications can be realized without departing from the claimed scope and spirit of this disclosure. [Explanation of Symbols]

[0093] 1, 101, 201 Semiconductor laser elements 1a 1st page 1b 2nd side 2 circuit boards 3 Semiconductor layer 4. Insulating material 5 1st electrode 6 Second electrode 10 1st layer 11 First n-side semiconductor layer 12. Second n-side semiconductor layer 20 2nd layer 21 First p-side semiconductor layer 22 Second p-side semiconductor layer 30 Active layer 50, 150 waveguides 51 1st end face 52 Second end face 53 Narrow part 54, 154 wide section 55 First area 56 Second area 60, 260, 560 diffraction gratings 61, 261 First protrusion 62, 262 Second protrusion 63 First recess 70 Ridge 80 Mask Patterns 81 Protective film 91 Light source section 92 Collimating Lens 93 Diffraction grating for multiplexing 400 Light source device d1, d2 distance z1, z2 height y1~y4 width x1, x2 width D Direction of light propagation L1, L2 tangent Pitch X 1st direction Y Second direction Z 3rd direction

Claims

1. circuit board and A waveguide including an active layer is provided, and a semiconductor layer portion is disposed on the substrate, Equipped with, The waveguide is, A wide section equipped with a diffraction grating, A narrow section having a waveguide width narrower than the wide section, in which light generated in the active layer propagates in transverse multimode, Includes, The waveguide comprises a first end face including the end face of the narrow portion, and a second end face located on the opposite side of the first end face. The aforementioned wide portion is, A first region is continuously connected to the aforementioned narrow portion, and the waveguide width widens from the first end face side to the second end face side, A semiconductor laser element equipped with the following features.

2. The waveguide further includes a second region, The second region is continuously connected to the first region. The waveguide width in the second region is constant. The semiconductor laser element according to claim 1, wherein the second region includes the diffraction grating.

3. The semiconductor layer includes a first semiconductor layer having a first refractive index and a second semiconductor layer having a second refractive index different from the first refractive index. The semiconductor laser element according to claim 1, wherein in the diffraction grating, one or more first protrusions provided on the surface of the first semiconductor layer and one or more second protrusions provided on the surface of the second semiconductor layer are periodically arranged in the direction of light propagation in the diffraction grating.

4. The semiconductor laser element according to claim 3, wherein the first semiconductor layer is disposed between the active layer and the second semiconductor layer.

5. The semiconductor laser element according to claim 3, wherein each of the first and second protrusions is arranged parallel to the second end face.

6. The semiconductor laser element according to claim 3, wherein each of the first and second protrusions is arranged to curve convexly from the first end face side to the second end face side.

7. The semiconductor laser element according to claim 6, wherein the tangents to the inner circumference of each of the first protrusions and the tangents to the inner circumference of each of the second protrusions are parallel to the wavefront of the propagating light.

8. A semiconductor laser element according to any one of claims 1 to 7, wherein 90% or more of the total output of light emitted from the second end face is contained within a wavelength range of 0.01 nm to 0.5 nm.

9. The semiconductor laser element according to any one of claims 1 to 7, wherein the waveguide width of the portion where the diffraction grating is provided is two times or more and four times or less the waveguide width in the narrow portion.

10. The semiconductor laser element according to any one of claims 1 to 7, wherein the waveguide width in the narrow portion is 15 μm or more and 90 μm or less.

11. The semiconductor laser element according to any one of claims 1 to 7, wherein the waveguide width of the portion where the diffraction grating is provided is 30 μm or more and 360 μm or less.

12. The distance from the first end face to the diffraction grating is an integer m and the effective refractive index n of each transverse mode. ｅｆｆ And the wavelength λ of each transverse mode in a vacuum 0 And, using, (m+1 / 4)×λ 0 / n ｅｆｆ A semiconductor laser element according to any one of claims 1 to 7, expressed as follows.

13. The M of light emitted from the second end face ２ The semiconductor laser element according to any one of claims 1 to 7, wherein the factor is 5 or more and 50 or less.

14. Multiple light sources, A diffraction grating for wave multiplexing is provided, Each of the aforementioned plurality of light sources is A semiconductor laser element according to any one of claims 1 to 7, The system comprises a collimating lens provided at the position into which light emitted from the semiconductor laser element is incident, The diffraction grating for wave multiplexing is a light source device that combines light emitted from the plurality of light source units.

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