laser device

Abstract

To suppress the relative difference in the emission directions (optical axes) of a plurality of beams of a multi-beam semiconductor laser element.SOLUTION: A multi-beam semiconductor laser element 100 is of an edge-emitting type and emits a plurality of beams. A plurality of laser resonators 140_1 to 140_n are integrated adjacently on a semiconductor substrate 110 in a first direction (x direction). Each of the plurality of laser resonators 140_1 to 140_n has a stripe-type current confinement structure extending in a second direction orthogonal to the first direction. The respective extending directions D1 to Dn of the plurality of laser resonators 140_1 to 140_n are non-parallel at least in a certain region on the emission end face side of the multi-beam semiconductor laser element.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] Multi-beam semiconductor laser devices have been proposed as high-power edge-emitting lasers, in which multiple ridge-stripe laser cavities are monolithically integrated. Some of these multi-beam semiconductor laser devices can be mounted with each ridge electrically isolated, enabling independent operation of multiple beams.

[0003] In the above-mentioned multi-beam semiconductor laser device, it is required to suppress relative differences in properties such as wavelength, polarization angle, light emission efficiency, and optical output among the multiple beams.

[0004] One of the factors that causes the relative difference in characteristics is thought to be the various stresses that semiconductor lasers receive when they are mounted on a submount. For example, Patent Document 1 points out that when assembling a semiconductor chip and a submount, stress caused by the difference in thermal expansion coefficient between the electrode material and semiconductor material on the semiconductor chip side and the solder material and submount material on the submount side affects the ridge portion, resulting in poor polarization angle characteristics. Polarization angle characteristics refer to the characteristics of the angle of polarization of light emitted from the emitter.

[0005] Patent Document 1 discloses a technology for suppressing the relative difference in polarization angle characteristics between beams. Specifically, by joining the solder material on the submount side to the bank portions provided on both sides of the ridge portion, with grooves between them, the solder material is prevented from being directly joined to the ridge portion, thereby suppressing the polarization angle rotation and relative polarization angle difference caused by stress from the solder material. This structure is also called a floating ridge structure. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-22481 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-245207 [Patent Document 3] Japanese Patent Application Laid-Open No. 2010-080867 Summary of the Invention [Problem to be solved by the invention]

[0007] As a result of studying the ridge floating structure, the present inventors have come to recognize the following problems.

[0008] Laser devices with a floating ridge structure have a problem in that the emission angles of multiple beams are not aligned. Specifically, it has been found that the optical axes of beams emitted from multiple laser resonators are not perpendicular to the emission end face of the chip, but are tilted toward the center of the chip. Note that a similar problem may also occur in laser devices other than those with a floating ridge structure. Note that this problem should not be considered common technical knowledge among those skilled in the art, but is something that the inventors have independently recognized.

[0009] An aspect of the present disclosure has been made in light of such circumstances, and one exemplary purpose thereof is to provide a multi-beam semiconductor laser element that can emit multiple beams in the same direction, in other words, that suppresses the relative difference between the emission directions (optical axes) of the multiple beams. [Means for solving the problem]

[0010] One aspect of the present disclosure is an edge-emitting multi-beam semiconductor laser device. The multi-beam semiconductor laser device includes a plurality of laser cavities integrated adjacently in a first direction on a semiconductor substrate. Each of the plurality of laser cavities has a stripe-shaped current confinement structure extending in a second direction perpendicular to the first direction. The extending directions of the plurality of laser cavities are non-parallel at least in a first region on the side of the emitting end face. Note that the "first region" in the present disclosure may refer to a region provided in the resonator direction and having the function of adjusting the emission direction of a laser beam. As will be described in detail later, for example, a region that realizes the above function by adjusting the angle of extension of a ridge stripe structure formed near the end face in the resonator direction, the stripe width, etc., may correspond to this first region.

[0011] 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]

[0012] According to an aspect of the present disclosure, the relative difference between the emission directions of multiple beams can be suppressed. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic perspective view of a multi-beam semiconductor laser element. [Figure 2] FIG. 1 is a cross-sectional view of a multi-beam semiconductor laser device. [Figure 3] 3(a) and 3(b) are diagrams illustrating the manufacturing process of a laser device including a multi-beam semiconductor laser element. [Figure 4] 4(a) to 4(d) are diagrams illustrating the difference in the emission directions of the two beams in the laser device of FIG. [Figure 5]1 is a plan view of a multi-beam semiconductor laser device according to a first embodiment. [Figure 6] 6(a) and 6(b) are diagrams for explaining the uniformity of the emission directions of the multi-beams by the multi-beam semiconductor laser element of FIG. [Figure 7] 7(a) and (b) are diagrams for explaining a simulation model. [Figure 8] 8(a) to 8(d) are diagrams showing the simulation results of the light intensity distribution in the comparative configuration. [Figure 9] 9(a) and 9(b) are diagrams showing the simulation results of the light intensity distribution in the waveguide corresponding to Example 1. FIG. [Figure 10] FIG. 10 is a plan view of a multi-beam semiconductor laser device according to a second embodiment. [Figure 11] 11(a) to 11(c) are diagrams for explaining the extending direction of the laser resonator. [Figure 12] FIG. 10 is a plan view of a multi-beam semiconductor laser device according to a third embodiment. [Figure 13] 13(a) and 13(b) are diagrams showing a part of a wafer of the multi-beam semiconductor laser device of FIG. 5 and the multi-beam semiconductor laser device of FIG. [Figure 14] FIG. 10 is a plan view of a multi-beam semiconductor laser device according to a fourth embodiment. [Figure 15] FIG. 10 is a plan view of a multi-beam semiconductor laser device according to a fifth embodiment. [Figure 16] FIG. 10 is a plan view of a multi-beam semiconductor laser device according to a sixth embodiment. [Figure 17] 17(a) and 17(b) are diagrams showing simulation results of the NFP and FFP in the horizontal direction (x direction) of the multi-beam semiconductor laser device of FIG. [Figure 18] FIG. 10 is a plan view of a multi-beam semiconductor laser device according to a seventh embodiment. [Figure 19] FIG. 13 is a plan view of a multi-beam semiconductor laser device according to an eighth embodiment. [Figure 20] FIG. 13 is a plan view of a multi-beam semiconductor laser device according to Example 9. [Figure 21] FIG. 20 is a plan view of a multi-beam semiconductor laser device according to a tenth embodiment. [Figure 22] FIG. 20 is a plan view of a multi-beam semiconductor laser device according to an eleventh embodiment. [Figure 23] FIG. 22 is a plan view of a multi-beam semiconductor laser device according to Example 12. [Figure 24] 24(a) and 24(b) are diagrams showing simulation results of the NFP and FFP in the horizontal direction (x direction) of the beams in the multi-beam semiconductor laser device of FIG. [Figure 25] 25(a) and 25(b) are plan views of a multi-beam semiconductor laser device according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0014] (Outline of the embodiment) A summary of some exemplary embodiments of the present disclosure is provided. This summary is intended to provide a simplified overview of some concepts of one or more embodiments in order to provide a basic understanding of the embodiments as a prelude to the more detailed description that follows. It 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.

[0015] An edge-emitting multi-beam semiconductor laser device according to one embodiment includes a plurality of laser cavities integrated adjacent to each other in a first direction on a semiconductor substrate. Each of the laser cavities has a stripe-shaped current confinement structure extending in a second direction perpendicular to the first direction. The extending directions of the laser cavities are non-parallel to each other at least in a first region on the side of the output end face.

[0016] When the chip is subjected to stress in its laser resonators in the final product state, stress-induced changes in the refractive index of the laser resonator's waveguide occur. If the stress is non-uniform across the chip's surface, the refractive index change in the laser resonator's waveguide causes the light's waveguiding direction to bend toward the direction of the higher refractive index. In one embodiment, when the chip is subjected to stress in the final product state, the relative differences in the emission directions of beams from the multiple laser resonators are suppressed. This can be achieved by individually designing the extension direction of each laser resonator according to its position, taking into account the refractive index distribution in the waveguide of each of the multiple laser resonators.

[0017] The extension direction of the laser cavity may be understood as the direction of the center line of the width direction (first direction) of the laser cavity. If the center line includes a curve, the extension direction may be understood as the tangent direction. The extension direction of the laser cavity may be understood as the average of the extension direction of one side boundary of the waveguide of the laser cavity and the extension direction of the other side boundary.

[0018] In one embodiment, the stripe-type current confinement structure may be a ridge structure or a buried structure (also called a buried ridge structure).

[0019] In one embodiment, the width of each of the plurality of laser cavities may be constant in the first region.

[0020] In one embodiment, in the first region, each of the plurality of laser resonators may have a tapered shape that widens toward the output end face. In another embodiment, in the first region, each of the plurality of laser resonators may have a tapered shape that narrows toward the output end face.

[0021] In one embodiment, each of the plurality of laser cavities may have the same width at the first end face and the same width at the second end face of the multi-beam semiconductor laser device.

[0022] In one embodiment, the extending direction of the multiple laser cavities may change at least once. The position of each of the multiple laser cavities in the first direction on the first end facet of the multi-beam semiconductor laser element may be the same as the position of each of the multiple laser cavities in the first direction on the second end facet. Details of this configuration will be described later with reference to FIG. 13 . The position in the first direction indicates the location where the resonator is formed when one end face of a chip constituting the element is used as a reference. Specifically, the distance from one end face of the chip to the center of the resonator in the first direction is the same on the first end face side and the second end face side. In the manufacturing process, when multiple chips are cut out from a wafer, the laser cavities are continuous at the boundary (cleavage plane) between two adjacent chips in the second direction, which improves the tolerance for misalignment of the cleavage plane in the second direction.

[0023] In one embodiment, in the second region adjacent to the first region on the side of the output end face, the extending direction of the plurality of laser cavities may be perpendicular to the output end face.

[0024] In one embodiment, the length of the second region in the second direction may be shorter than the length of the first region in the second direction. By making the length of the second region sufficiently short, the beam is emitted in a direction corresponding to the extension direction of the first region.

[0025] In one embodiment, the plurality of laser cavities may include a first laser cavity and a second laser cavity. The first laser cavity and the second laser cavity may be formed symmetrically with respect to a center line of the chip in the first direction. When stress is generated symmetrically with respect to the center line of the chip, the design of the multi-beam semiconductor laser device can be simplified.

[0026] In one embodiment, when the extension direction of the laser resonators is defined as an angle with respect to the second direction, the angle of each of the multiple laser resonators may be larger the farther the laser resonator is from the center line of the semiconductor substrate in the first direction.

[0027] A laser device according to an embodiment may include a multi-beam semiconductor laser chip and a support substrate supporting the multi-beam semiconductor laser chip, wherein the multi-beam semiconductor laser chip and the support substrate may have different thermal expansion coefficients.

[0028] (Embodiment) The present disclosure will be described below based on preferred embodiments with reference to the drawings. The same or equivalent components, parts, and processes shown in each drawing are designated by the same reference numerals, and redundant descriptions will be omitted where appropriate. Furthermore, the embodiments are illustrative and do not limit the disclosure, and all features and combinations thereof described in the embodiments are not necessarily essential to the disclosure.

[0029] 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.

[0030] First, differences in the emission directions of a plurality of beams in a multi-beam semiconductor laser element will be described.

[0031] FIG. 1 is a schematic perspective view of a multi-beam semiconductor laser device 100. The multi-beam semiconductor laser device 100 is an edge-emitting type and is configured to be able to emit multiple beams BM1 to BMn from multiple n (n≧2) emitters 102_1 to 102_n adjacent to each other in a first direction (x direction in the figure). A configuration or function corresponding to one beam is also referred to as a channel. FIG. 1 exemplarily shows a configuration where n=2.

[0032] The multi-beam semiconductor laser device 100 includes n laser cavities 140_1 to 140_n corresponding to n beams, and is monolithically formed on a single semiconductor substrate 110. The n laser cavities 140_1 to 140_n have a stripe-shaped current confinement structure extending in a second direction (y direction in the figure). As the current confinement structure, a ridge structure, a buried structure (buried ridge structure), or the like can be adopted.

[0033] Fig. 2 is a cross-sectional view of the multi-beam semiconductor laser device 100. The multi-beam semiconductor laser device 100 in Fig. 2 has a ridge structure. The multi-beam semiconductor laser device 100 includes n=2 emitters 102_1 and 102_2 and can emit two beams.

[0034] The multi-beam semiconductor laser device 100 includes a semiconductor substrate 110, a multilayer structure 120, an insulating film 134, a p-side electrode 138, and an n-side electrode 139. The multilayer structure 120 includes, for example, an n-type cladding layer 122, an emission layer 124 (also referred to as an optical waveguide core layer) including a guide layer and a quantum well layer, a p-type cladding layer 126, and a p-type contact layer 128. Each layer is further divided into smaller layers based on its composition and doping concentration. The multilayer structure 120 is formed by epitaxial growth using, for example, MOCVD (Metal Organic Chemical Vapor Deposition).

[0035] A laser cavity (laser structure) 140 having a ridge stripe structure is formed in the multilayer structure 120. The ridge stripe structure can be formed by partially removing the p-type contact layer 128 and the p-type cladding layer 126, for example, by using photolithography and etching techniques. When forming the ridge structure in each p-type cladding layer 126, a bank structure may be formed in each p-type cladding layer 126. Each bank may be provided on both sides of each ridge structure, or on only one side. Alternatively, the bank structure may be omitted.

[0036] If it is desired to make a plurality of laser cavities 140 independently controllable, a separation groove 150 may be formed.

[0037] The upper surface of the p-type contact layer 128 is covered with an insulating film 134 such as SiO2. The insulating film 134 has an opening in the area of ​​the laser resonator 140. A p-side electrode 138 formed on the upper layer of the insulating film 134 is electrically connected to the p-type contact layer 128 through the opening in the insulating film 134. An n-side electrode 139 is formed on the back surface of the semiconductor substrate 110, and electricity is passed between the p-side electrode 138 and the n-side electrode 139.

[0038] It should be noted that the cross-sectional structure of the multi-beam semiconductor laser device 100 in FIG. 2 is merely an example and does not limit the present disclosure in any way.

[0039] The above is the basic structure of the multi-beam semiconductor laser element 100. The multi-beam semiconductor laser element 100 is mounted on a support substrate to form a laser device.

[0040] 3(a) and (b) are diagrams illustrating a manufacturing process of a laser device 200 including a multi-beam semiconductor laser element 100. The laser device 200 includes the multi-beam semiconductor laser element 100 shown in FIG. 1 and a support substrate 210 that supports the multi-beam semiconductor laser element 100. The support substrate 210 is also called a submount. In FIGS. 3(a) and (b), the multi-beam semiconductor laser element 100 is shown upside down compared to FIG. 2.

[0041] 3(a) shows the state before die bonding, and FIG. 3(b) shows the state after die bonding. Solder 212 is applied to the surface of the support substrate 210. The multi-beam semiconductor laser device 100 is mounted on the support substrate 210 with the p-side electrode 138 in contact with the solder 212.

[0042] A material with excellent heat dissipation properties can be selected for the support substrate 210. For example, consider mounting a chip of a multi-beam semiconductor laser device 100 having a GaAs semiconductor substrate 110 on an AlN support substrate 210. Because the thermal expansion coefficient of GaAs is larger than that of AlN, after a welding process with a solder material at approximately 400°C, GaAs shrinks more than AlN during the cooling process. In FIG. 3(b), arrow 300 schematically represents the shrinkage of the semiconductor substrate 110, and arrow 302 schematically represents the shrinkage of the support substrate 210.

[0043] As a result of the differential shrinkage of the semiconductor substrate 110 and the support substrate 210, a shear stress is applied to the ridge structure of the laser cavity 140, as indicated by arrows 304. This shear stress is smaller closer to the centerline 112 of the semiconductor substrate 110 and larger closer to the periphery.

[0044] Figures 4(a) to 4(d) are diagrams for explaining the difference in the emission directions of two beams in the laser device 200 of Figure 3. Figure 4(a) shows the laser device 200. The laser device 200 of Figure 4(a) is an inverted version of the laser device 200 of Figure 3(b). The center position of the chip of the multi-beam semiconductor laser element 100 is defined as x0, and the center positions of the laser resonators 140_1 and 140_2 are defined as x1 and x2, respectively.

[0045] 4(b) is a diagram showing the refractive index distribution in the waveguides of the laser resonators 140_1 and 140_2. In the waveguide of the laser resonator 140_1, the refractive index becomes higher as one approaches the center x0 of the chip, i.e., toward the right on the page. In the waveguide of the laser resonator 140_2, the refractive index becomes higher as one approaches the center x0 of the chip, i.e., toward the left on the page.

[0046] Due to the influence of the refractive index distribution in the waveguide, the light guided in the waveguide is biased toward the center of the chip, where the refractive index is higher. Figure 4(c) shows the near-field patterns (NFP) of the beams BM1 and BM2 generated by the two laser resonators 140_1 and 140_2. The NFP represents the intensity distribution in the x-direction at the output end facet of the multi-beam semiconductor laser device 100. Due to the influence of the refractive index distribution, the peak of the NFP of the beam BM1 generated by the laser resonator 140_1 is shifted toward the x0 side from the x1 side. Similarly, the peak of the NFP of the beam BM2 generated by the laser resonator 140_2 is shifted toward the x0 side from the x2 side.

[0047] Figure 4(d) shows the far-field patterns (FFP) of the beams BM1 and BM2 generated by the two laser resonators 140_1 and 140_2. The FFP is plotted with the horizontal axis representing the horizontal emission angle θh. As a result of the polarization of light within each waveguide, each beam is emitted in a different oblique direction (non-perpendicular) to the emission end face of the chip. In other words, multiple beams are emitted at different angles.

[0048] It should be noted that the problem of different emission directions of multiple beams and the mechanism thereof described here should not be considered as common knowledge among those skilled in the art.

[0049] Hereinafter, a technique for suppressing differences in the emission directions of a plurality of beams will be described based on several examples.

[0050] Example 1 5 is a plan view of a multi-beam semiconductor laser device 100A according to a first embodiment. The multi-beam semiconductor laser device 100A includes a plurality of laser cavities 140_1 to 140_n integrated adjacent to each other in a first direction (x direction) on a semiconductor substrate 110. Here, n=2. As described above, each of the plurality of laser cavities 140_1 to 140_n has a stripe-type current confinement structure extending in a second direction (y direction) perpendicular to the first direction (x direction). S1 denotes an emitting end face of the multi-beam semiconductor laser device 100A, and S2 denotes a surface opposite to the emitting end face.

[0051] The stripes of the laser cavity 140 having a current confinement structure extend in the y direction when viewed macroscopically, but extend in a direction shifted from the y direction when viewed microscopically. The extension directions of the multiple laser cavities 140_1 to 140_n (indicated by arrows D1 and D2 in the figure) are designed to be non-parallel to each other. This design is made so that when the chip of the multi-beam semiconductor laser element 100A is mounted on the laser device 200, in other words, when stress is generated in the multi-beam semiconductor laser element 100A, the multiple beams emitted from the laser cavities 140_1 to 140_n become nearly parallel. Note that in the drawing, the difference between the extension directions D1 and D2 is exaggerated, but in reality it is much smaller than what is shown, less than 1°. The extension directions D1 and D2 are represented as inclination angles θ1 and θ2 formed with an imaginary line parallel to the y axis.

[0052] In the first embodiment, the width of the laser cavity 140_1 is constant over the entire range in the y direction, and the same is true for the laser cavity 140_2.

[0053] The above is the configuration of the multi-beam semiconductor laser device 100A. Next, the operation thereof will be described.

[0054] 6(a) and 6(b) are diagrams illustrating the uniformity of the emission directions of multiple beams by the multi-beam semiconductor laser device 100A of FIG. 5. FIG. 6(a) shows the emission directions of the beams when the laser resonator 140 is not subjected to stress. When the laser resonator 140 is not subjected to stress, the refractive index distribution in the x direction within the laser resonator 140 is uniform, so the propagation direction of the beam BMi (i = 1, 2 ...) coincides with the extension direction Di of the laser resonator 140_i. When no stress is applied, the beams BM1 and BM2 are emitted in directions DO1 and DO2. Due to the difference in refractive index between the laser resonator 140 and air, the beam BM is refracted at the emission end face S1, so the extension direction Di and the emission direction DOi do not coincide.

[0055] FIG. 6(b) shows the beam emission direction when the laser resonator 140 is subjected to stress. When the laser resonator 140_i is subjected to stress, a gradient occurs in the refractive index distribution within the laser resonator 140_i. As a result, the light guided within the laser resonator 140_i is guided while being slightly bent toward the center of the chip, where the refractive index is high. The guide direction Di' of the light within the laser resonator 140_i is tilted by Δθi toward the center line 112 of the chip with respect to the extending direction Di of the resonator. Furthermore, at the emitting end face S1, the beam BM guided in the direction Di' is refracted due to the refractive index difference between the laser resonator 140 and air, and the beam BMi is emitted in the radiation direction DOi'. In this way, by adjusting the extending direction Di of the laser resonator in accordance with the stress, the laser beams emitted from the laser resonators 140_1 and 140_2 are emitted parallel to each other.

[0056] The above is the operation of the multi-beam semiconductor laser device 100A.

[0057] By designing the extension directions D1 to Dn (inclination angles θ1 to θn) of the multiple laser resonators 140_1 to 140_n so that the optical axis change amounts Δθ1 to Δθn due to the refractive index distribution based on stress can be canceled, the relative difference in the emission directions (optical axes) of the multiple beams BM1, BM2 can be suppressed in the state of the laser device 200 in which the laser resonator 140 is subjected to stress, and the multiple beams BM1 to BMn can be made parallel.

[0058] Consider a case where the stress distribution in the laser resonator 140 occurs symmetrically with respect to the center line 112 of the semiconductor substrate 110. If the positions of the emitters 102_1 and 102_2 of the two laser resonators 140_1 and 140_2 are equidistant from the center line 112, stresses of the same magnitude are applied to the two laser resonators 140_1 and 140_2 in opposite directions, so that the magnitudes of the optical axis shifts Δθ1 and Δθ2 are equal. Therefore, the inclination angles θ1 and θ2 of the extension directions D1 and D2 of the laser resonators 140_1 and 140_2 are adjusted so that the emission direction of the laser beam is perpendicular to the end face, and in this embodiment, the inclination angles θ1 and θ2 are equal. In other words, the laser resonator 140 may be designed to be axisymmetric with respect to the center line 112 of the semiconductor substrate 110 and so that the emission direction of the laser beam is perpendicular to the end face.

[0059] There may be cases where the geometric center line 112 of the semiconductor substrate 110 does not coincide with the center of the stress. In this case, the multi-beam semiconductor laser device 100A may be designed to be symmetrical with respect to the center line of the stress.

[0060] The simulation results of the multi-beam semiconductor laser device 100A will be described. Figures 7(a) and 7(b) are diagrams illustrating a simulation model. In the simulation, the laser resonator 140 is treated as a waveguide WG1 with surface A as the incident end and surface B as the output end. The width W of the waveguide WG1 is 1.5 μm, and the length L of the waveguide WG1 is 300 μm.

[0061] Figure 7(b) shows the refractive index distribution in the x direction within the waveguide WG1 in the simulation model. To simplify the calculation, the refractive index n is assumed to change stepwise within the waveguide, being 3.20 at the center of the waveguide WG1, 3.20 + 0.0005 towards the center of the chip, and 3.20 - 0.0005 at the outside of the chip.

[0062] First, a simulation of a configuration (referred to as a comparative configuration) in which the extending direction of the waveguide WG1 is aligned with the y-axis will be described.

[0063] 8(a) to 8(d) are diagrams showing the results of a simulation of the light intensity distribution in a comparative configuration. FIG. 8(a) shows the intensity distribution of light incident on the input end A of the waveguide WG1. Here, the incident light L1 has a Gaussian distribution. In the figure, light with an intensity of 50% of the peak light intensity is incident on the waveguide WG1. The portion with a light intensity of less than 50% indicates the portion that spreads from the waveguide WG1 to the periphery, and is in the range of approximately ±2 μm from 0 on the horizontal axis.

[0064] 8(b) shows the NFP in the horizontal direction (x direction) at the output end B of the waveguide WG1. Due to the influence of the refractive index distribution, the maximum intensity of the NFP at the output end B is biased toward the center of the chip.

[0065] Figure 8(c) shows the FFP in the horizontal direction (x direction) when it is assumed that there is no refraction due to the difference in refractive index between the waveguide WG1 and air. This shows the directivity of the beam just before the output end face in the waveguide WG1. It can be seen that the propagation direction of the beam BM1 is tilted by Δθ = 0.13° toward the center due to the influence of the refractive index distribution in the waveguide WG1.

[0066] Figure 8(d) shows the FFP in the horizontal direction (x direction) when the difference in refractive index between the waveguide WG1 and air is taken into account. Due to the tilt Δθ of the propagation direction and the influence of refraction at the output facet B, the beam BM1 is emitted with an inclination of 0.4° toward the center.

[0067] Next, a simulation of the waveguide corresponding to Example 1 in which the extending direction of the waveguide WG1 is tilted by θ=0.04° from the y-axis will be described with reference to FIGS. 9(a) and 9(b).

[0068] 9(a) and 9(b) are diagrams showing the results of a simulation of the light intensity distribution of the waveguide corresponding to Example 1. Fig. 9(a) shows the NFP in the horizontal direction (x direction) at the output end face of the waveguide WG1, and Fig. 9(b) shows the FFP in the horizontal direction (x direction). By tilting the waveguide WG1 by 0.04° with respect to the y axis, the peak of the FFP can be set to 0°, in other words, the beam can be output parallel to the y axis.

[0069] Example 2 10 is a plan view of a multi-beam semiconductor laser device 100B according to Example 2. In Example 1, the distances between the laser resonators 140_1 and 140_2 and the center line 112 are equal, but the present disclosure is not limited to this.

[0070] In the second embodiment, the laser resonators 140_1 and 140_2 are disposed at different distances l1 and l2 from the center line 112. In FIG. 10, l2>l1 holds. As described above, the stress increases with increasing distance from the center line 112 of the semiconductor substrate 110, and therefore the refractive index change in the laser resonator 140_2 is greater than that in the laser resonator 140_1. As a result, the optical axis shift amount Δθ caused by the refractive index change is greater in the laser resonator 140_2 (Δθ2>Δθ1). In this case, the inclination angle θ2 of the extension direction D2 of the laser resonator 140_2 may be designed to be greater than the inclination angle θ1 of the extension direction D1 of the laser resonator 140_1.

[0071] In the first and second embodiments, the width of each laser cavity 140_i is constant, but the present disclosure is not limited to this. The extending direction of the waveguide when the width of the laser cavity 140 is not constant will be described.

[0072] 11(a) to 11(c) are diagrams illustrating the extension direction of the laser cavity 140. A portion of the ridge stripe structure of the laser cavity 140 is shown in 11(a) to 11(c). D is a vector indicating the extension direction. θ is the angle between the vector D and an imaginary line parallel to the y-axis, and the extension direction can be expressed using this angle θ.

[0073] 11(a) shows a ridge stripe structure with a constant width, while Figures 11(b) and 11(c) show a ridge stripe structure with a tapered shape whose width increases toward the light-emitting end face. As shown in Figures 11(a) and 11(b), an imaginary line CL is taken that passes through the centers of the edges El and Er of the ridge stripe structure, and the direction along this imaginary line CL can be set as the extension direction D of the laser cavity 140.

[0074] 11(c), the extending directions Dl and Dr of the edges El and Er of the ridge stripe structure may be taken, and the direction obtained by averaging or vector synthesis of the two extending directions Dl and Dr may be taken as the extending direction D of the laser cavity 140. Alternatively, the extending direction θ of the laser cavity 140 may be taken as the average of the directions θl and θr of the extending directions Dl and Dr.

[0075] The extension direction of the laser cavity 140 is not limited to that described here. For example, if the ridge stripe structure includes a curve, the extension direction can be the tangent direction of a virtual line CL passing through the center. In the following description, the extension direction D is defined as the direction along the center line CL, as shown in Figures 11(a) and 11(b).

[0076] Example 3 12 is a plan view of a multi-beam semiconductor laser device 100C according to Example 3. In Example 3, each laser cavity 140_i has a tapered shape, and the width of each cavity gradually changes in the y direction.

[0077] In Example 3, the extending directions D1 and D2 of the laser resonators 140_1 and 140_2 are also non-parallel to each other. Of the two side edges En and Ef of each laser resonator 140, the edge En closer to the center line 112 is perpendicular to the light-emitting end face S1 of the chip, and the edge Ef farther from the center line 112 is inclined with respect to the light-emitting end face S1 of the chip.

[0078] The advantage of the multi-beam semiconductor laser device 100C of Fig. 12 over the multi-beam semiconductor laser device 100A of Fig. 5 will be described with reference to Fig. 13. This advantage is related to the manufacturing process of the multi-beam semiconductor laser device.

[0079] 13(a) and 13(b) are diagrams showing a portion of a wafer of the multi-beam semiconductor laser device 100A of FIG. 5 and the multi-beam semiconductor laser device 100C of FIG. 12. After the pre-processing is completed, the multi-beam semiconductor laser device 100C is continuous within the wafer and is separated into individual chips by dicing. 13(a) and 13(b) show ideal dicing lines 410A and actual dicing lines 410.

[0080] 13(a), in the configuration of Example 1 (FIG. 5), if the dicing line 410 is deviated in the y direction from the ideal dicing line 410A, a discontinuity 412 occurs in the laser resonator 140, causing it to cease functioning as a laser. In other words, the configuration of Example 1 is very sensitive to the position of the dicing line.

[0081] 13(b), in the configuration of Example 3 (FIG. 12), even if dicing line 410 is shifted in the y direction, the width of laser resonator 140 changes stepwise at portion 414, but the laser resonator is not interrupted as in FIG. 13(a). In other words, according to Example 3, the tolerance for shifting of dicing line in the y direction can be increased compared to Example 1.

[0082] Example 4 14 is a plan view of a multi-beam semiconductor laser device 100D according to Example 4. In Example 4, similarly to Example 3, each laser resonator 140_i has a tapered shape, and the extending directions D1 and D2 of the laser resonators 140_1 and 140_2 are non-parallel to each other.

[0083] 14, of the two side edges of each laser resonator 140, the edge Ef farther from the center line 112 is perpendicular to the output end face S1 of the chip, and the edge En closer to the center line 112 is inclined with respect to the output end face S1 of the chip. In order to achieve the same extension directions D1 and D2 as in FIG. 12, in FIG. 14, the width of the laser resonator 140 in the first direction (x direction) becomes narrower as it approaches the output end face S1, and the width becomes wider as it moves away from the output end face S1.

[0084] The emission directions of a plurality of beams can also be aligned according to the fourth embodiment. The third embodiment has the following advantages over the fourth embodiment.

[0085] If the width of the output end face is narrow, in other words, if the area of ​​the emitter is small, there is a problem that the electric field of light is concentrated and the temperature rise increases. From this viewpoint, by making the inner edge En parallel to the y-axis as in Example 3, it is possible to increase the width of the output end face, i.e., the area of ​​the emitter, while maintaining the adjusted state of the output direction of the laser light, thereby solving this problem.

[0086] Example 5 15 is a plan view of a multi-beam semiconductor laser device 100E according to Example 5. In Examples 1 to 4, the extension directions of the multiple laser cavities 140 are non-parallel over the entire range in the y direction. In contrast, in Example 5, the extension directions of the multiple laser cavities 140 are non-parallel over a portion of the range in the y direction, but are parallel over another portion of the range in the y direction. Specifically, in a region A1 close to the output end face S1, the extension directions D1 and D2 of the multiple laser cavities 140 are non-parallel, and in a region A2 far from the output end face S1, the extension directions of the multiple laser cavities 140 are parallel. This configuration also makes it possible to suppress differences in the emission directions of the multiple beams.

[0087] Example 6 16 is a plan view of a multi-beam semiconductor laser device 100F according to Example 6. Example 6 is a combination of Examples 3 and 5. That is, in region A1, the extending directions D1 and D2 are non-parallel, and in region A2, the extending directions D1 and D2 are parallel. In addition, in region A1, the laser resonators 140_1 and 140_2 have a tapered shape.

[0088] 17(a) and 17(b) are diagrams showing simulation results of the NFP and FFP in the horizontal direction (x direction) of the multi-beam semiconductor laser device 100F of Fig. 16. The width W2 of the laser cavity 140 in region A2 is set to 1.5 μm, and the width W1 of the laser cavity 140 at the output end face S1 of region A1 is set to 2.3 μm. The length of region A1 is 300 μm, and the inclination angle of the extension directions D1 and D2 is set to 0.15°.

[0089] As shown in FIG. 17(b), by giving the laser resonator 140 a tapered shape and designing the extension direction, the peak of the FFP is in the 0° direction, and it becomes possible to emit a beam parallel to the y-axis.

[0090] Example 7 18 is a plan view of a multi-beam semiconductor laser device 100G according to Example 7. In Example 7, a region A3 is added compared to Example 6. In the region A3, the laser resonator 140_i has a tapered shape so that the width of the laser resonator 140_i is equal between the end face S1 and the end face S2.

[0091] According to Example 7, even if the dicing line is shifted in the y direction during the manufacturing process, the continuity of the waveguide can be ensured. In Example 3 already described, if the dicing line is shifted, the width of the laser cavity changes in a step-like manner. However, in Example 7, even if the dicing line is shifted, the width of the laser cavity remains continuous, which is advantageous compared to Example 3.

[0092] Example 8 19 is a plan view of a multi-beam semiconductor laser device 100H according to Example 8. In Example 8, regions A0 and A4 are added compared to Example 7. In the regions A0 and A4, the widths of the laser resonators 140_i are constant and are equal to W1. In addition, the extending direction of the laser resonators 140_i in the regions A0 and A4 coincides with the y-axis direction.

[0093] In the eighth embodiment, if the length Ls of the region A0 is sufficiently shorter than the length Lt of the region A1 (Ls<<Lt), the emission direction of the beam is predominantly determined by the extension direction of the region A1.

[0094] According to Example 8, the continuity of the waveguide can be ensured even when the dicing line is shifted in the y direction, as in Example 7. In particular, in Example 8, the widths of the regions A0 and A4 are equal to W1, so that the width of the output end can be kept constant even when the dicing line is shifted in the y direction.

[0095] Example 9 20 is a plan view of a multi-beam semiconductor laser device 100I according to Example 9. In Example 9, similar to Example 5 (FIG. 15), the width of the laser resonators 140_i is constant. In Example 9, a region A3 is added compared to Example 5. In this region A3, the extending direction of the laser resonators 140_i is changed, and the width and position of the laser resonators 140_i at the two end faces S1 and S2 are the same.

[0096] According to the ninth embodiment, the beam emission direction can be controlled by the extending direction of the laser resonator 140_i in the region A1. Furthermore, by adding the region A3, the continuity of the waveguide can be ensured even if the dicing line is shifted in the y direction.

[0097] Example 10 21 is a plan view of a multi-beam semiconductor laser device 100J according to Example 10. In Example 10, regions A0 and A4 are added compared to Example 9 (FIG. 20). In the regions A0 and A4, the width of the laser resonator 140_i is constant, and the extending direction coincides with the y-axis direction.

[0098] According to Example 10, the continuity of the waveguide can be ensured even when the dicing line is shifted in the y direction, as in Example 9. In particular, in Example 10, the widths of regions A0 and A4 are constant and the extension directions coincide with the y-axis direction, so there is a greater tolerance for the shift of the dicing line in the y direction.

[0099] Example 11 22 is a plan view of a multi-beam semiconductor laser device 100K according to Example 11. Example 11 includes an additional region A2 compared to Example 3 (FIG. 21). In region A2, the width of the laser resonator 140_i is changed so that the width and position of the laser resonator 140_i are the same at the two end faces S1 and S2.

[0100] According to the eleventh embodiment, the beam emission direction can be controlled by the extending direction Di of the laser resonator 140_i in the region A1. Furthermore, by adding the region A2, the continuity of the waveguide can be ensured even if the dicing line is shifted in the y direction.

[0101] Example 12 23 is a plan view of a multi-beam semiconductor laser device 100L according to Example 12. In Examples 1 to 11, the extending direction of the laser resonator 140 is designed so that all beams are emitted perpendicular to the emitting end face S2, but the present disclosure is not limited thereto, and the extending direction may be designed so that all beams are emitted in the same non-perpendicular direction.

[0102] 23, the extending direction of the laser resonator 140_2 coincides with the y-axis direction, and the beam BM2 of the laser resonator 140_2 is emitted in a direction non-perpendicular to the output end face S1. The extending direction D1 of the laser resonator 140_1 is designed so that the output direction DO1 of the beam BM1 coincides with the output direction DO2 of the beam BM2.

[0103] 24(a) and (b) are diagrams showing simulation results of the NFP and FFP in the horizontal direction (x direction) of beam BM1 in the multi-beam semiconductor laser device 100L of FIG. 23. As shown in FIG. 8(d), the peak of the FFP of beam BM2 of laser cavity 140_2 is shifted by 0.4° toward the center. When the extending direction D1 of laser cavity 140_1 is designed with an inclination angle θ1=0.17°, a beam parallel to laser cavity 140_2 can be output. The FFP of beam BM1 shown in FIG. 24(b) is shifted by 0.4°, and the two beams BM1 and BM2 can be made parallel.

[0104] (Variation) The above-described embodiments and examples are merely examples, and it will be understood by those skilled in the art that various modifications are possible in the combination of the respective components and the respective processing steps. Such modifications will be described below.

[0105] 25(a) and (b) are plan views of a multi-beam semiconductor laser device according to a modified example. The multi-beam semiconductor laser device 100a in FIG. 25(a) has n=3, includes three laser resonators 140_1 to 140_3, and is capable of emitting three beams BM1 to BM3. The central laser resonator 140_2 is formed along the center line 112 of the chip at θ2=0°. The laser resonators 140_1 and 140_3 on both ends are formed at equal distances from the center line 112 of the chip and line-symmetrically with respect to the center line 112 so that the three beams BM1 to BM3 are equally spaced apart.

[0106] The multi-beam semiconductor laser device 100b in FIG. 25(b) has n=4, includes four laser resonators 140_1 to 140_4, and is capable of emitting four beams BM1 to BM4. To equalize the intervals between the four beams BM1 to BM4, the centers of the four laser resonators 1401 to 140_4 on the output end face S1 are equally spaced. Preferably, the multiple laser resonators 140_1 to 140_4 are configured to be axisymmetric with respect to the center line 112. Furthermore, the inclination angles θ1 and θ4 of the laser resonators 140_1 and 140_4 farther from the center line 112 are designed to be larger than the inclination angles θ2 and θ3 of the laser resonators 140_2 and 140_3 closer to the center line 112.

[0107] 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]

[0108] 100... multi-beam semiconductor laser element, 102... emitter, 110... semiconductor substrate, 120... multilayer structure, 122... n-type cladding layer, 124... light-emitting layer, 126... p-type cladding layer, 128... p-type contact layer, 134... insulating film, 138... p-side electrode, 139... n-side electrode, 140... laser resonator, 150... separation groove, 200... laser device, 210... supporting substrate, 212... solder

Claims

1. A support substrate; an edge-emitting multi-beam semiconductor laser chip mounted on the support substrate by solder; Equipped with a thermal expansion coefficient of the chip of the multi-beam semiconductor laser element is different from a thermal expansion coefficient of the support substrate; The multi-beam semiconductor laser device is a plurality of laser cavities integrated adjacent to each other in a first direction on a semiconductor substrate; each of the plurality of laser resonators has a stripe-type current confinement structure extending in a second direction perpendicular to the first direction; a first region of the laser cavity on the side of an output end face of the laser device, the first region being non-parallel to the first region of the laser cavity, so that a plurality of output beams from the laser cavity are parallel to each other;

2. 2. The laser device according to claim 1, wherein the width of each of the plurality of laser resonators is constant in the first region.

3. 2. The laser device according to claim 1, wherein in the first region, each of the plurality of laser resonators has a tapered shape whose width increases as it approaches the light-emitting end face.

4. 2. The laser device according to claim 1, wherein in the first region, each of the plurality of laser resonators has a tapered shape in which the width narrows toward the light-emitting end face.

5. 5. The laser device according to claim 3, wherein each of the plurality of laser resonators has a width equal to a width at a first end face of the multi-beam semiconductor laser element and a width equal to a width at a second end face of the multi-beam semiconductor laser element.

6. 5. The laser device according to claim 2, wherein the extending direction of the plurality of laser resonators changes at least once.

7. 7. The laser device according to claim 6, wherein the position of a first end face of the multi-beam semiconductor laser element in the first direction and the position of a second end face of the multi-beam semiconductor laser element in the first direction are the same for each of the plurality of laser resonators.

8. 7. The laser device according to claim 6, wherein in a second region adjacent to the first region on the side of the light-emitting end face, the extending direction of the plurality of laser cavities is perpendicular to the light-emitting end face.

9. The laser device according to claim 8 , wherein the length of the second region in the second direction is shorter than the length of the first region in the second direction.

10. the plurality of laser cavities include a first laser cavity and a second laser cavity; 2. The laser device according to claim 1, wherein the first laser resonator and the second laser resonator are formed symmetrically with respect to a center line of the semiconductor substrate in the first direction.

11. When the extending direction of the laser resonator is defined as an angle with respect to the second direction, The laser device according to claim 1 , wherein the angle of each of the plurality of laser resonators increases as the laser resonator is farther from a center line of the semiconductor substrate in the first direction.

Images