Semiconductor laser element

Abstract

To provide a semiconductor laser that is suppressed from forming interference fringes in an FFP.SOLUTION: A semiconductor laser element 100 has a light shield groove 170 formed in an upper clad layer 126 adjacently to a bank 160 in a waveguide direction. A surface of the light shield groove 170 is covered with an insulation layer (not shown in the figure), and the light shield groove 170 is deep enough to reach an absorption layer which is one of a substrate 110 and a buffer layer formed on the substrate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a semiconductor laser device. [Background technology]

[0002] Laser diodes (LDs) are used as light sources for laser pointers. In particular, red and infrared LDs are often used as light sources for pointers, but blue and green LDs are also becoming more common. In recent years, there has been an increasing demand for pointers with a clearer visible light spot and for them to be recognized by sensors or cameras. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5378651 [Patent Document 2] Japanese Patent Publication No. 2020-127003 [Patent Document 3] Patent No. 4830315 [Patent Document 4] Japanese Patent Application Laid-Open No. 2013-143550 Summary of the Invention [Problem to be solved by the invention]

[0004] If interference fringes occur in the far-field pattern (FFP), which is the image of the laser beam emitted by the semiconductor laser, a clear light spot cannot be formed.

[0005] An embodiment of the present disclosure has been made in light of this situation, and one exemplary purpose thereof is to provide a semiconductor laser that suppresses the occurrence of interference fringes in FFP. [Means for solving the problem]

[0006] One aspect of the present disclosure relates to an edge-emitting semiconductor laser device, which includes a stacked structure of a lower cladding layer, an active layer, and an upper cladding layer formed on a semiconductor substrate, a ridge portion formed in the upper cladding layer, a bank formed in the upper cladding layer adjacent to the ridge portion in the width direction, and a light-shielding groove formed in the upper cladding layer adjacent to the bank in the waveguide direction.

[0007] Any combination of the above elements, or mutual substitution of elements or expressions between methods, devices, systems, etc., are also valid aspects of the present invention or the present disclosure. Furthermore, the description in this section (Means for Solving the Problems) does not explain all essential features of the present invention, and therefore, subcombinations of the described features may also constitute the present invention. [Effects of the Invention]

[0008] According to an aspect of the present disclosure, it is possible to suppress the occurrence of interference fringes in a beam pattern (referred to as a far field pattern: FFP) at a position away from the light-emitting end face of a semiconductor laser element. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view of a semiconductor laser element according to an embodiment. [Figure 2] FIG. 2 is a diagram schematically showing the beam intensity of the semiconductor laser element of FIG. [Figure 3] 2 is a cross-sectional view of the semiconductor laser device of FIG. 1, taken perpendicular to the x-axis. [Figure 4] 10A and 10B are diagrams illustrating the blocking of stray light by a light-blocking groove. [Figure 5] FIG. 10 is a cross-sectional view of a semiconductor laser device according to a comparative technique. [Figure 6] FIG. 10 is a cross-sectional view of a semiconductor laser device according to a first modification. [Figure 7] FIG. 10 is a cross-sectional view of a semiconductor laser device according to Modification 2. [Figure 8]10A and 10B are diagrams showing modified examples of the cross-sectional shape of the light-shielding groove in a plane perpendicular to the x-axis. [Figure 9] FIG. 11 is a perspective view of a semiconductor laser device according to Modification 4. [Figure 10] FIG. 11 is a perspective view of a semiconductor laser device according to Modification 5. [Figure 11] 1A to 1C are diagrams showing three structures of a semiconductor laser element. [Figure 12] FIG. 10 is a diagram showing calculated values ​​of errors between the beam profile and the Gaussian distribution for each of the first to third structures. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Outline of the embodiment) A summary of some exemplary embodiments of the present disclosure is provided below. This summary is intended as a prelude to the more detailed description that follows, or to provide a basic understanding of the embodiments. This summary is intended to briefly explain some concepts of one or more embodiments and is not intended to limit the scope of the invention or disclosure. Furthermore, this summary is not an exhaustive overview of all possible embodiments, nor does it limit essential elements of the embodiments. For convenience, the term "one embodiment" may refer to one embodiment (example or variant) or multiple embodiments (examples or variants) disclosed herein.

[0011] (Outline of the embodiment) An edge-emitting semiconductor laser device according to one embodiment includes a stacked structure of a lower cladding layer, an active layer, and an upper cladding layer formed on a semiconductor substrate, a ridge portion formed in the upper cladding layer, a bank formed in the upper cladding layer adjacent to the ridge portion in the width direction, and a light-shielding groove formed in the upper cladding layer adjacent to the bank in the waveguide direction. This blocks light propagating from the bank, thereby suppressing interference fringes. For example, the "bank" refers to a support portion formed in the upper cladding layer to match the height of the ridge portion, and is formed to protect the ridge portion from external collisions and stresses during bonding, for example.

[0012] In one embodiment, the refractive index of the lower cladding layer is higher than that of the upper cladding layer, the surface of the light-shielding groove is covered with an insulating layer, and the depth of the light-shielding groove may reach an absorption layer, which is either the substrate or a buffer layer formed on the substrate, i.e., the insulating layer and the absorption layer may contact or intersect at some parts.

[0013] A portion of the light guided through the ridge portion couples with the bank and is guided through the bank. In an asymmetric cladding where the refractive index of the lower cladding layer is higher than that of the upper cladding layer, the light guided through both the ridge portion and the bank is attracted toward the lower cladding layer. In such a configuration, if the light-shielding groove is shallow, the light emitted from the bank passes through a portion deeper than the light-shielding groove, forming interference fringes in the FFP. The above-mentioned semiconductor laser element is configured so that the light-shielding groove reaches the absorption layer. Light emitted from the end face of the bank couples with the insulating layer of the light-shielding groove, is guided through the insulating layer, and is guided to the absorption layer and absorbed. This prevents the light emitted from the bank from forming interference fringes. The absorption layer is a material whose forbidden band width is smaller than the forbidden band width of the active layer, which determines the emission wavelength, and absorbs laser light and stray light.

[0014] In one embodiment, the angle of incidence of the light beam with respect to the light-shielding groove at the depth where the intensity of the light beam reaches its peak is greater than 0°. More preferably, the angle of incidence is greater than 5°, and even more preferably, greater than 10°. The greater the angle of incidence, the greater the coupling to the insulating layer.

[0015] In one embodiment, the Al composition ratio of the upper cladding layer may be higher than the Al composition ratio of the lower cladding layer by 0.01 or more.

[0016] In one embodiment, the thickness of the lower cladding layer may be thicker than the thickness of the upper cladding layer, thereby ensuring a clearance between the light guided through the ridge portion and the absorption layer, and suppressing a decrease in efficiency.

[0017] In one embodiment, the ridge may be wider in an output region near the output facet.

[0018] In one embodiment, the cross-sectional shape of the light-shielding groove may be non-linear, in other words, curved, on the bank side.

[0019] In one embodiment, the semiconductor substrate may be a GaAs substrate. In this case, when the oscillation wavelength is light in the red region, the GaAs substrate can be used as an absorption layer. Note that the expression "light having an oscillation wavelength in the red region" may also be simply referred to as "the oscillation wavelength is red."

[0020] In one embodiment, the light-shielding groove may have an end in the width direction that extends beyond the side of the bank facing the ridge portion toward the ridge portion. By bringing the end of the light-shielding groove closer to the ridge portion, stray light emitted from the bank can be more reliably blocked, and interference fringes can be suppressed.

[0021] An edge-emitting semiconductor laser device according to one embodiment includes a laminated structure of a lower cladding layer, an active layer, and an upper cladding layer formed on a semiconductor substrate, a ridge portion formed in the upper cladding layer, a bank formed in the upper cladding layer adjacent to the ridge portion in the width direction, and a light-shielding groove formed in the upper cladding layer adjacent to the bank in the waveguide direction. The refractive index of the lower cladding layer is higher than that of the upper cladding layer, and an end of the light-shielding groove protrudes toward the ridge portion in the width direction beyond the side of the bank facing the ridge portion.

[0022] By bringing the end of the light-shielding groove close to the ridge portion, stray light emitted from the bank can be more reliably blocked, and interference fringes can be suppressed.

[0023] (Embodiment) The present disclosure will be described below with reference to the drawings based on preferred embodiments. The same or equivalent components, parts, and processes shown in each drawing will be given the same reference numerals, and redundant explanations will be omitted as appropriate. Furthermore, the embodiments are examples rather than limitations on the disclosure, and all features and combinations thereof described in the embodiments are not necessarily essential to the disclosure.

[0024] The dimensions (thickness, length, width, etc.) of each component shown in the drawings may be enlarged or reduced as appropriate for ease of understanding. Furthermore, the dimensions of multiple components do not necessarily represent their relative sizes. Even if a component A is drawn thicker than another component B in the drawings, it is possible that component A is thinner than component B.

[0025] (Embodiment) 1 is a perspective view of a semiconductor laser device 100 according to an embodiment. The semiconductor laser device 100 is an edge-emitting type, and emits a laser light (beam) BM1 from an output end face S1. A laser resonator 140 is formed between the output end face S1 and a reflecting end face S2 of the semiconductor laser device 100. S1 and S2 are also referred to as the front end face and the rear end face, respectively.

[0026] The laser cavity 140 is formed on a semiconductor substrate 110. On the semiconductor substrate 110, a stacked structure (multilayer growth layer) 120 is formed, including a lower cladding layer 122, which is an n-type cladding layer, an active layer 124, an upper cladding layer 126, which is a p-type cladding layer, and a p-type contact layer 128. Although not shown in detail, an (interface) layer with a stepwise change in composition may be provided between the upper cladding layer 126 and the contact layer 128 in order to reduce the band notch. For example, in the case of a semiconductor laser with a red oscillation wavelength, AlGaInP is used for the cladding layer and GaAs is used for the contact layer. The composition of the layer that reduces the band notch mentioned above includes AlGaInP and AlGaAs, and the Al composition can be changed stepwise or continuously.

[0027] The laser cavity 140 is formed using the multilayer growth layer 120. The upper cladding layer 126 is ridge-processed for current confinement, and has a ridge portion 150. Electrodes are necessary for the operation of the laser cavity 140, but they are not shown in the figure because they can be formed in appropriate locations using known techniques.

[0028] In the drawing, the width direction of the laser resonator 140 is taken as the x-axis, the direction perpendicular to the semiconductor substrate 110 as the y-axis, and the length direction of the laser resonator 140, i.e., the guide direction of the laser light, as the z-axis. In this specification, "viewing the laser resonator 140 from above" means viewing the laser resonator 140 from a direction perpendicular to the semiconductor substrate 110, i.e., viewing the laser resonator 140 along the y-axis. Also, "viewing the output end surface S1 of the laser resonator 140 from the front" means viewing the laser resonator 140 along the z-axis.

[0029] Furthermore, in the upper cladding layer 126, a bank 160 is formed adjacent to the ridge portion 150 in the width direction (x-axis direction).

[0030] Furthermore, in the upper cladding layer 126, a light-shielding groove 170 is formed adjacent to the bank 160 in the waveguiding direction (z-axis direction).

[0031] In this embodiment, the laser cavity 140 has an asymmetric cladding structure, and the refractive index n n is the refractive index n of the upper cladding layer 126 p Specifically, the upper cladding layer 126 has a higher Al composition ratio than the lower cladding layer 122. For example, when the oscillation wavelength is red or infrared, the cladding layer generally contains (Al x Ga (1-x) ) 0.5 In 0.5 Here, a structure in which the Al composition ratio x of the lower cladding layer 122 is lower than that of the upper cladding layer is called an asymmetric cladding structure. The p-type upper cladding layer 126 is doped with an impurity such as Mg, and the n-type lower cladding layer 122 is doped with an impurity such as Si, but in order to obtain good characteristics, the impurity concentration of the upper cladding layer 126 is generally made higher than that of the lower cladding layer 122.

[0032] FIG. 2 is a diagram schematically illustrating the beam intensity of the semiconductor laser device 100 of FIG. 1. This beam intensity shows the intensity distribution in a plane perpendicular to the z-axis at the end (z=z0) of the bank 160 of FIG. 1. Laser light L1 emitted as beam BM1 is guided in the Z-axis direction directly below the ridge portion 150. Stray light L2 is also guided in the Z-axis direction directly below the bank 160. As described above, the semiconductor laser device 100 has an asymmetric structure in which the refractive index of the lower cladding layer 122 is higher than that of the upper cladding layer 126. Therefore, the laser light L1 spreads more toward the lower cladding layer 122. This reduces the amount of light seeping into the upper cladding layer 126, reducing light absorption in the GaAs absorption layer used as the contact layer 128 when the oscillation wavelength is red or infrared, and thus improving the slope efficiency of the current-light output characteristics. Furthermore, when the impurity concentration of the upper cladding layer 126 is made higher than that of the lower cladding layer 122, more light is distributed in the lower cladding layer 122, which has a lower impurity concentration, thereby reducing internal loss caused by free carrier loss. In order to obtain good characteristics, it is desirable that the difference in Al composition ratio x between the upper cladding layer 126 and the lower cladding layer 122 be 0.01 or more, and by appropriately setting the film thickness of the lower cladding layer 122, it is possible to suppress absorption of laser light by an absorption layer located below (on the substrate side of) the lower cladding layer 122, and the difference in Al composition ratio x may be made even larger (for example, 0.3 or more) to further increase the polarization of light.

[0033] When the oscillation wavelength is red, a GaAs substrate may be used as the semiconductor substrate 110, which absorbs red light. In such a configuration, if the lower cladding layer 122 is thin, the laser light L1 is absorbed by the semiconductor substrate 110, resulting in reduced efficiency. Therefore, it is preferable that the thickness of the lower cladding layer 122 is thicker than that of the upper cladding layer 126. The substrate material may be any material that absorbs light of the oscillation wavelength, and may be, for example, an InP substrate or a GaN substrate.

[0034] The stray light L2 is also biased toward the lower cladding layer 122, similar to the laser light L1.

[0035] 3 is a cross-sectional view perpendicular to the x-axis of the semiconductor laser device 100 of FIG. 1. The upper part of FIG. 3 shows a cross-section at the center (x=x0) of the ridge portion 150 in the x-axis direction, and the lower part shows a cross-section at the center (x=x1) of the bank 160. The surface of the upper cladding layer 126 of the semiconductor laser device 100 is covered with an insulating film 180. This insulating film 180 also extends into the light-shielding groove 170, and the surface of the light-shielding groove 170 is covered with the insulating film 180. Furthermore, the insulating film 180 may be covered with a metal film 182.

[0036] 2, stray light L2 is guided below the bank 160. The light-shielding groove 170 blocks the stray light L2 and prevents it from being emitted from the output end surface S1.

[0037] FIG. 4 illustrates the blocking of stray light L2 by the light-shielding groove 170. The left side of FIG. 4 shows the intensity distribution of stray light L2 in the depth direction. The cross-sectional view of FIG. 4 shows the ray (principal ray) of stray light L2 at depth y0 where the intensity is maximum. The incident surface 172 of the light-shielding groove 170 is formed non-parallel to the xy plane. Therefore, the stray light L2 is incident non-perpendicularly to the incident surface 172 of the light-shielding groove 170. Reference numeral 174 denotes the incident point, 176 denotes the tangent to the incident surface 172 at the incident point, and 178 denotes the normal to the incident surface 172 at the incident point. In other words, the incident angle θ formed by the stray light L2 and the normal 178 is greater than 0°. The incident angle θ should be 5° or greater, and preferably 10° or greater. The larger the incident angle θ, the more easily the stray light L2 is coupled to the insulating film 180.

[0038] At the incident point 174, a portion L2a of the stray light L2 is reflected by the insulating film 180 and directed toward the semiconductor substrate 110. The forbidden band width of the semiconductor substrate 110 is smaller than the forbidden band width of the active layer 124, which determines the emission wavelength, and the semiconductor substrate 110 is an absorption layer that absorbs the stray light L2, so the reflected light L2a directed toward the semiconductor substrate 110 is absorbed by the semiconductor substrate 110.

[0039] At the incident point 174, a portion L2b of the stray light L2 enters the insulating film 180 and is guided using the insulating film 180 as a waveguide. Since the insulating film 180 reaches the semiconductor substrate 110, which is an absorption layer, the light L2b guided within the insulating film 180 is absorbed by the semiconductor substrate 110 near the lowest part of the light-shielding groove 170.

[0040] A portion L2c of the light L2b that has been guided within the insulating film 180 may be emitted from the insulating film 180 again to the lower cladding layer 122, but this light L2c is directed toward the semiconductor substrate 110 and is therefore absorbed by the semiconductor substrate 110.

[0041] When the metal film 182 is formed on the insulating film 180, the metal film 182 functions as a reflective film, and therefore it is possible to prevent a part L2c of the light L2b guided within the insulating film 180 from leaking toward the light-shielding groove 170 side.

[0042] However, the metal film 182 is not essential and may be omitted. In this case, a waveguide that utilizes the difference in refractive index between air and the insulating film 180 may be used to suppress leakage of light toward the light-shielding groove 170 side.

[0043] According to this semiconductor laser device 100, the stray light L2 guided through the bank 160 can be shielded by the light-shielding groove 170, and the stray light L2 emitted from the output end face S1 can be significantly reduced. This makes it possible to prevent the stray light L2 guided through the bank 160 and the laser light L1 guided through the ridge portion 150 from forming interference fringes in the far field, and to form a clear spot.

[0044] The advantages of the semiconductor laser device 100 become clear when compared with comparative techniques.

[0045] 5 is a cross-sectional view of a semiconductor laser device 100R according to the comparative technology. In the comparative technology, the light-shielding groove 170R does not reach the semiconductor substrate 110, which is an absorption layer. In this configuration, stray light L2d guided at a position y2 lower than the depth y1 of the lowest part of the light-shielding groove 170R can be guided to the output end face S1 without being blocked by the light-shielding groove and can be emitted from the output end face S1.

[0046] Furthermore, a portion L2e of the light L2b guided within the insulating film 180 is guided to the output end face side without being absorbed by the semiconductor substrate 110 at the lowest part of the light-shielding groove 170R. This light L2e is emitted to the lower cladding layer 122 on the output end face S1 side, and light L2f is emitted from the output end face S1.

[0047] Thus, in the comparative technique, the beam BM2 caused by the stray lights L2d and L2f is emitted and interferes with the beam BM1 in the far field to form an unclear light spot.

[0048] The semiconductor laser device 100 according to the embodiment can solve the problems encountered in the comparative techniques.

[0049] Next, a modification of the semiconductor laser device 100 will be described.

[0050] (Variation 1) 6 is a cross-sectional view of a semiconductor laser device 100A according to Modification 1. A light-shielding groove 170A is dug deeper toward the lower surface side than the upper interface of the semiconductor substrate 110. Other points are the same as those of the embodiment.

[0051] (Variation 2) 7 is a cross-sectional view of a semiconductor laser device 100B according to Modification 2. In this modification, a buffer layer 112 is formed on a semiconductor substrate 110 in order to improve the crystallinity of the multilayer growth layer 120, and the multilayer growth layer 120 is then formed on the buffer layer 112. The buffer layer 112 is used as an absorption layer, and the depth of the light-shielding grooves 170B reaches the buffer layer 112. For example, when the emission wavelength range is in the red range, GaAs is often used for the absorption layer. However, the absorption layer may be made of AlGaInP, AlGaAs, InP, or other III-V group semiconductor materials as long as the material has a composition smaller than the forbidden band width of the active layer, which determines the emission wavelength.

[0052] (Variation 3) Next, modified examples of the cross-sectional shape of the light-shielding groove 170 will be described.

[0053] 8 is a diagram showing modified examples of the cross-sectional shape of the light-shielding groove 170 in a plane perpendicular to the x-axis. In the figure, the right side (+z direction) is the emission end face S1, and the left side (-z direction) is the reflection end face S2. In all of the light-shielding grooves 170a to 170f, the incidence surface 172 on the reflection end face S2 side is formed as a curved surface. The light-shielding groove 170a has a shape that follows a circular arc. The light-shielding grooves 170b and 170c have a shape that follows an ellipse, with the depth direction (y-axis direction) of the ellipse being the major axis of the ellipse in the light-shielding groove 170b and the depth direction (y-axis direction) of the ellipse being the minor axis of the ellipse in the light-shielding groove 170c.

[0054] In the light-shielding groove 170d, the incident surface 172 is formed as a paraboloid.

[0055] The cross section of the light-shielding groove 170 may be asymmetric. There are no particular restrictions on the shape or inclination angle of the light-emitting surface 173 of the light-shielding groove 170, and therefore, as shown in light-shielding groove 170e, the light-emitting surface 173 may be a substantially vertically cut flat surface.

[0056] Like the light-shielding groove 170f, it may be formed along a bathtub shape.

[0057] (Variation 4) 9 is a perspective view of a semiconductor laser device 100 according to Modification 4. The ridge portion 150 has a wider width in an emission region 152 near the emission end face S1. In this modification, the width of the ridge portion 150 in the emission region 152 is equal to the length from end to end of the two banks 160. Note that the width and shape of the emission region 152 are not limited to those shown in FIG. 9. Other points are the same as those of the embodiment.

[0058] (Variation 5) 10 is a perspective view of a semiconductor laser device according to Modification 5. The light-shielding groove 170 is formed in contact with the output end face S1. In this modification, the lowest portion of the light-shielding groove 170 is located at the output end face S1, but the position in the Z-axis direction where the light-shielding groove 170 is formed is not limited to that shown in FIG. 10 as long as it is formed in the vicinity of the output end face S1 so as to prevent stray light L2 guided through the bank 160 from being emitted from the output end face S1. Other points are the same as those of the embodiment.

[0059] The above explanation has focused on the characteristics of the light-shielding groove 170 in the depth direction (y-axis direction). Next, a preferred structure of the light-shielding groove 170 in the x-axis direction (width direction of the resonator) will be described.

[0060] Three structures were considered for the length (width) of the light-shielding groove 170 in the x-axis direction.

[0061] 11 shows three structures 200a to 200c of the semiconductor laser device 100. For each of the structures 200a to 200c, (i) a plan view, (ii) a cross-sectional view at z=z1, and (iii) the light intensity distribution (beam profile) in the horizontal direction (x-axis direction) at depth y0 where the intensity is maximum is shown. The cross-sectional view schematically shows the beam patterns of laser light L1 guided through the ridge portion 150 and stray light L2 guided through the bank 160.

[0062] In the first structure 200a, with respect to the x-axis direction, the tip of the light-shielding groove 170 in the x-axis direction protrudes toward the ridge portion 150 beyond the inner side e1 of the bank 160. In this structure, the light-shielding groove 170 blocks stray light L2.

[0063] In the second structure 200b, the tip of the light-shielding groove 170 in the x-axis direction is located outside the inner side e1 of the bank 160. In this structure, a portion of the stray light L2 close to the ridge portion 150 remains without being completely blocked by the light-shielding groove 170.

[0064] The third structure 200c has a structure in which the light-shielding groove 170 is omitted.

[0065] The beam profile was calculated by simulation for each of the first to third structures 200a to 200c. The error of each beam profile from a Gaussian distribution was then calculated. The error was calculated by integrating the intensity and the error of the Gaussian distribution along the x-axis.

[0066] 12 is a diagram showing the deviation of the beam profile from the Gaussian distribution for each of the first to third structures 200a to 200c. In the structure 200a in which the end 171 of the light-shielding groove 170 protrudes toward the ridge portion 150 side beyond the side e1 of the bank 160, the deviation from the Gaussian distribution is 3.9×10 -4 In the structure 200b in which the end 171 of the light-shielding groove 170 is located outside the side e1 of the bank 160, the error from the Gaussian distribution is 7.7×10 -3 In the structure 200c without the light-shielding groove 170, the error is 4.6×10 -1 And even bigger.

[0067] Comparing the structures 200a and 200b, the error in the structure 200a is smaller by more than one order of magnitude, which means that the structure 200a can suppress interference fringes in the far field more effectively than the structure 200b.

[0068] The embodiments merely illustrate the principles and applications of the present invention, and many modifications and changes in arrangement are permitted to the embodiments as long as they do not deviate from the spirit of the present invention as defined in the claims. [Explanation of symbols]

[0069] 100 Semiconductor laser element S1 Output end face S2 reflective end face 110 Semiconductor substrate 112 Buffer layer 120 Multilayer growth layer 122 Lower cladding layer 124 Active layer 126 Upper cladding layer 150 Ridge 152 Output area 160 banks 170 Light-shielding groove 140 Laser Cavity 180 insulating film

Claims

1. An edge-emitting semiconductor laser element, a laminated structure of a lower cladding layer, an active layer, and an upper cladding layer formed on a semiconductor substrate; a ridge portion formed in the upper cladding layer; a bank formed in the upper cladding layer adjacent to the ridge portion in a width direction; a light-shielding groove formed in the upper cladding layer adjacent to the bank in a waveguide direction; A semiconductor laser device comprising:

2. the refractive index of the lower cladding layer is higher than the refractive index of the upper cladding layer, 2. The semiconductor laser element according to claim 1, wherein the surface of the light-shielding groove is covered with an insulating layer, and the depth of the light-shielding groove reaches an absorption layer which is either the substrate or a buffer layer formed on the substrate.

3. 3. The semiconductor laser device according to claim 1, wherein the angle of incidence of the light beam with respect to said light-shielding groove at the depth at which the intensity of the light beam reaches its peak is greater than 0[deg.].

4. 3. The semiconductor laser device according to claim 1, wherein the Al composition ratio of said upper cladding layer is higher than the Al composition ratio of said lower cladding layer by 0.01 or more.

5. 3. The semiconductor laser device according to claim 1, wherein the thickness of the lower cladding layer is greater than the thickness of the upper cladding layer.

6. 3. The semiconductor laser device according to claim 1, wherein the ridge portion has a wider width in an emission region in the vicinity of the emission end face.

7. 3. The semiconductor laser device according to claim 1, wherein the light-shielding groove is formed in contact with the light-emitting end face.

8. 3. The semiconductor laser device according to claim 1, wherein the cross-sectional shape of the light-shielding groove in the cavity direction is non-linear on the bank side.

9. 3. The semiconductor laser device according to claim 1, wherein the semiconductor substrate is a GaAs substrate.

10. 3. The semiconductor laser device according to claim 1, wherein the light-shielding groove has an end portion in a width direction that protrudes toward the ridge portion beyond a side of the bank that faces the ridge portion.

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