Multibeam semiconductor laser element and method for manufacturing the same

Abstract

To easily or inexpensively manufacture a semiconductor laser having a plurality of oscillation wavelengths.SOLUTION: In an edge emitting multi-beam semiconductor laser device 100, a laminated structure 130 includes a substrate 110, an n-type clad layer 122, a light-emitting layer 124, and a p-type clad layer 126. In the laminated structure 130, the combined height of the substrate 110 and the n-type cladding layer 122 is different in m (m≥2) regions adjacent in the first direction. n (2≤n≤m) of the m regions are formed with n laser resonators 140 having a ridge stripe structure extending in a second direction perpendicular to the first direction.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] As a high-power edge-emitting laser, a multi-beam semiconductor laser in which a plurality of ridge stripe type laser resonators are monolithically integrated has been proposed (Patent Document 1).

Prior Art Documents

Patent Documents

[0003] [[ID=2l]]

Patent Document 1

Non-Patent Documents

[0004]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] (Problem 1) When using multi-beam semiconductor lasers as light sources for displays, if the wavelengths of the multiple beams are the same, interference between the beams causes undesirable intensity distributions (interference fringes) in the far-field pattern (FFP), resulting in a decrease in beam quality. To solve this beam quality problem, it is necessary to intentionally shift the oscillation wavelengths of multiple channels.

[0006] Edge-emitting lasers have a laminated structure consisting of a first conductivity cladding layer, an emission layer, and a second conductivity cladding layer. The oscillation wavelength of the laser resonator is primarily determined by the size and composition of the emission layer. Therefore, to monolithically form multiple laser resonators with different oscillation wavelengths, it is necessary to perform selective growth for each resonator or to repeatedly perform regrowth.

[0007] Selective growth is difficult with mixed crystal materials with a high Al composition, such as AlGaInP. Specifically, a high Al composition results in low selectivity, making it easy for polycrystals to deposit on the selection mask. Furthermore, adopting a regrowth process inevitably increases costs.

[0008] Non-patent documents 1 to 3 propose several techniques for shifting wavelengths, but all of them relate to vertical-cavity surface-emitting lasers and are not applicable to edge-emitting lasers.

[0009] (Task 2) In multi-beam semiconductor laser elements, light leakage between adjacent channels (optical crosstalk) negatively affects beam quality. A technique has been proposed to block light leakage between adjacent channels by providing separation grooves (Patent Document 1).

[0010] While isolation grooves can suppress optical crosstalk, they also hinder lateral heat conduction, leading to heat buildup in the emitter. Since semiconductor lasers experience a decrease in output characteristics (luminous efficiency) as the temperature rises, isolation grooves can cause variations in output characteristics between channels.

[0011] Some aspects of this disclosure have been made in such circumstances, and one exemplary objective is to provide a multibeam semiconductor laser element and a method for manufacturing the same that can solve at least one of the above-mentioned problems. [Means for solving the problem]

[0012] A particular aspect of this disclosure relates to an end-emitting multibeam semiconductor laser element. The multibeam semiconductor laser element comprises a laminated structure including a substrate, a first conductivity type cladding layer, an emission layer, and a second conductivity type cladding layer. In the laminated structure, the combined height of the substrate and the first conductivity type cladding layer differs for m (m≧2) adjacent regions in the first direction. In n (2≦n≦m) of the m regions, n laser resonators with a ridge-stripe structure extending in a second direction perpendicular to the first direction are formed, and at least two of the n laser resonators have different oscillation wavelengths.

[0013] Another aspect of the present disclosure relates to a method for manufacturing an end-emitting multibeam semiconductor laser element. This manufacturing method comprises the steps of: forming a substrate structure including a substrate and a first conductivity type cladding layer, wherein the thickness of the substrate structure differs for each m (m≧2) adjacent region in the first direction; forming an emission layer and a second conductivity type cladding layer on the substrate structure; and forming n laser resonators with a ridge-stripe structure extending in a second direction perpendicular to the first direction in n (2≦n≦m) of the m regions.

[0014] Furthermore, any combination of the above components, or any substitution of the components or expressions of this disclosure between methods, apparatus, systems, etc., are also valid forms of this disclosure. [Effects of the Invention]

[0015] According to certain aspects of this disclosure, at least one of the above-mentioned problems can be solved. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic perspective view of a multi-beam semiconductor laser device. [Figure 2] This is a cross-sectional view of a multi-beam semiconductor laser element according to Example 1. [Figure 3] Figure 2 illustrates the heat dissipation of a multi-beam semiconductor laser element. [Figure 4] Figure 2 illustrates the improvement in heat dissipation in a multi-beam semiconductor laser element. [Figure 5] Figures 5(a) to 5(f) show the manufacturing method for the multi-beam semiconductor laser device shown in Figure 2. [Figure 6] This is a cross-sectional view of a multi-beam semiconductor laser element according to Example 2. [Figure 7] Figures 7(a) to 7(d) show the manufacturing method for the multi-beam semiconductor laser device shown in Figure 6. [Figure 8] This is a cross-sectional view of the multi-beam semiconductor laser element according to Example 3. [Figure 9] Figures 9(a) to 9(g) are simplified cross-sectional views of a modified multi-beam semiconductor laser element. [Figure 10] This is a cross-sectional view of a multi-beam semiconductor laser element according to modified example 2. [Modes for carrying out the invention]

[0017] (Summary of the embodiment) This section outlines some exemplary embodiments of the present disclosure. This outline serves as a prelude to the detailed description that follows, or as a means of understanding the embodiments. This outline provides a simplified explanation of some concepts of one or more embodiments and does not limit the scope of the invention or disclosure. Furthermore, this outline is not a comprehensive overview of all possible embodiments and does not limit the essential components of the embodiments. For convenience, “one embodiment” may be used to refer to one embodiment (example or variation) or more embodiments (example or variation) disclosed herein.

[0018] An end-face emitting multi-beam semiconductor laser element according to one embodiment comprises a laminated structure including a substrate, a first conductivity type cladding layer, an emission layer, and a second conductivity type cladding layer. In the laminated structure, the combined height of the substrate and the first conductivity type cladding layer differs for each m (m≧2) adjacent region in the first direction. Of the m regions, n (2≦n≦m) have n laser resonators with a ridge-stripe structure extending in a second direction perpendicular to the first direction, and at least two of the n laser resonators have different oscillation wavelengths.

[0019] The inventors have independently recognized that when a light-emitting layer is deposited on a substrate with varying heights (hereinafter referred to as the substrate structure), the crystal growth conditions, specifically the gas flow rate, and consequently the deposition rate and composition, are determined according to the irregularities of the substrate structure. This disclosure is based on this recognition. That is, by making the thickness of the substrate and the n-type cladding layer non-uniform in each region, the growth conditions of the light-emitting layer differ in each region, making it possible to easily form multiple laser resonators with different oscillation wavelengths.

[0020] In one embodiment, the thickness of the substrate may differ for each m region. That is, the surface of the substrate may be non-flat and may have irregularities in the first direction. In this specification, the front and back of the substrate are defined as the side on which the laser resonator is formed and the back on the opposite side.

[0021] In this case, since the first conductivity type cladding layer, the light-emitting layer, and the second conductivity type cladding layer can be grown after forming irregularities on the substrate, multiple crystal growth processes are unnecessary, thus reducing manufacturing costs.

[0022] In one embodiment, the thickness of the substrate in the first region and the thickness of the substrate in the third region may be different.

[0023] This results in different deposition rates for the light-emitting layer in the first and third regions, allowing for a shift in the oscillation wavelength.

[0024] In one embodiment, the m regions may include adjacent first, second, and third regions. The thickness of the second region is greater than the thicknesses of the first and third regions, and laser resonators may be formed in the first and third regions, respectively.

[0025] The second region corresponds to a protrusion of the substrate structure, while the first and third regions correspond to a recess of the substrate structure. In this configuration, the substrate of the second region, which is a protrusion, can thermally and / or optically isolate the two laser resonators formed in the first and third regions.

[0026] In one embodiment, the light-emitting layer in the first region and the light-emitting layer in the third region may be located at a height lower than the surface of the substrate in the second region.

[0027] As a result, the heat generated in the first region's light-emitting layer and the heat generated in the third region's light-emitting layer are conducted to the substrate in the second region, thereby suppressing the temperature rise of the light-emitting layer.

[0028] In one embodiment, the substrate may be a material that absorbs light at the oscillation wavelength of the laser resonator.

[0029] This allows the substrate to suppress optical coupling between adjacent laser resonators.

[0030] In one embodiment, the substrate may contain GaAs when the oscillation wavelength is in the range of 580 to 900 nm, and may contain GaN when the oscillation wavelength is 360 nm or less. "Containing material A" is not limited to containing material A itself, but may also include containing a compound of material A, or containing material A doped with impurities or other materials.

[0031] In one embodiment, the m regions may further include a fourth region adjacent to the first region in the opposite direction to the second region, and a fifth region adjacent to the third region in the opposite direction to the second region. The widths of the first region and the third region may be different.

[0032] By controlling the widths of the first and third regions, the conditions for crystal growth (gas flow rate) in the light-emitting layer in the first and third regions can be controlled, and consequently, the oscillation wavelength of the laser resonator can be controlled.

[0033] In one embodiment, a laser resonator having a ridge-stripe structure may be further formed in the second region.

[0034] During crystal growth in the light-emitting layer, the crystal growth conditions differ between the second region corresponding to the convex portion and the first and third regions corresponding to the concave portion. This makes it easy to achieve three different wavelengths.

[0035] In one embodiment, the oscillation wavelength of the laser resonator in the second region may be longer than the oscillation wavelengths of the laser resonators in the first and third regions.

[0036] Due to the difference in deposition rates between the convex and concave areas, a longer-wavelength laser resonator is automatically formed in the second region corresponding to the convex area compared to the first and third regions corresponding to the concave area. While the second region corresponding to the convex area is less advantageous from a heat dissipation standpoint compared to the first and third regions corresponding to the concave area, longer-wavelength lasers are less affected by temperature than shorter-wavelength lasers. Therefore, even if the temperatures of multiple laser resonators are non-uniform, the non-uniformity of output caused by temperature differences can be eliminated.

[0037] In one embodiment, the thickness of the first conductive cladding layer may differ for each of the m regions.

[0038] Compared to cases where the substrate thickness varies from region to region, a process is required to control the thickness of the first conductive cladding layer, but this is significantly easier than selectively growing the light-emitting layer.

[0039] In one embodiment, a separation groove extending in a second direction may be further formed in the second region. By forming a separation groove in the second region, the multiple laser resonators can be electrically isolated without hindering lateral heat conduction from the laser resonators in the first region and the third region toward the substrate.

[0040] In one embodiment, a semiconductor or metal that absorbs light of the oscillation wavelength of the laser resonators may be placed between adjacent laser resonators.

[0041] A method for manufacturing an end-face emitting type multibeam semiconductor laser element according to one embodiment comprises the steps of: forming a base structure including a substrate and a first conductivity type cladding layer, wherein the thickness of the base structure differs for each m (m≧2) adjacent region in the first direction; forming an emitting layer and a second conductivity type cladding layer on the base structure; and forming n laser resonators with a ridge-stripe structure extending in a second direction perpendicular to the first direction in n (2≦n≦m) of the m regions.

[0042] According to this method, the light-emitting layer grows crystals on a substrate layer with irregularities (hereinafter also referred to as the substrate structure), and the crystal growth conditions in each region (such as the gas flow rate) are determined according to the irregularities of the substrate structure. This makes it easy to make the oscillation wavelengths of the n laser resonators different.

[0043] In one embodiment, the step of forming the base structure may include the step of forming grooves in the substrate that extend in a second direction, and the step of forming a first conductive cladding layer on the substrate on which the grooves have been formed. In this case, since the first conductive cladding layer, the light-emitting layer, and the second conductive cladding layer can be grown after the irregularities have been formed on the substrate, a crystal growth process divided into multiple steps is unnecessary, and manufacturing costs can be reduced.

[0044] In one embodiment, the step of forming grooves may include the step of forming multiple grooves of different widths. By controlling the width of the grooves, the conditions for crystal growth of the light-emitting layer in each groove (gas flow rate, flow velocity, concentration, etc.) can be controlled, and consequently, the oscillation wavelength of the laser resonator formed in each groove can be controlled.

[0045] (Embodiment) The present disclosure will be described below with reference to the drawings, based on preferred embodiments. The same or equivalent components, members, and processes shown in each drawing will be denoted by the same reference numerals, and redundant descriptions will be omitted where appropriate. Furthermore, the embodiments are illustrative and not limiting, and not all features or combinations thereof described in the embodiments are necessarily essential to the disclosure.

[0046] The dimensions (thickness, length, width, etc.) of each component shown in the drawing 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 component A is depicted as thicker than component B in the drawing, component A may actually be thinner than component B.

[0047] Figure 1 is a schematic perspective view of a multi-beam semiconductor laser element 100. The multi-beam semiconductor laser element 100 is an end-face emission type and is configured 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). The configuration and function corresponding to one beam are also called a channel.

[0048] The multi-beam semiconductor laser element 100 comprises n laser resonators 140_1 to 140_n corresponding to n beams, and is monolithically formed on a single chip (die). The n laser resonators 140_1 to 140_n have a ridge-stripe structure extending in the second direction (y-direction in the figure). As will be described later, the ridge-stripe structure is formed by partially removing the p-type cladding layer from a crystalline layer (epitaxial layer) that includes an n-type (first conductivity type) cladding layer, an emissive layer, and a p-type (second conductivity type) cladding layer. The ridge-stripe structure is also simply called a ridge or ridge structure. A bank (not shown in Figure 1) may be formed between two adjacent laser resonators 140.

[0049] The above describes the basic structure of the multi-beam semiconductor laser element 100. In this embodiment, the n laser resonators 140_1 to 140_n have different oscillation wavelengths λ1 to λ n It has the following characteristics: Oscillation wavelength λ1~λ n It is preferable that all of them are different, but some of them may have the same wavelength. Below, the specific configuration of the multi-beam semiconductor laser element 100 according to the embodiment will be described based on several examples.

[0050] (Example 1) Figure 2 is a cross-sectional view of a multi-beam semiconductor laser element 100A according to Example 1. The multi-beam semiconductor laser element 100A comprises a laminated structure 130. The laminated structure 130 includes a substrate 110, an n-type cladding layer 122, an emissive layer (also called an active layer) 124, and a p-type cladding layer 126. As described later, the n-type cladding layer 122, the emissive layer 124, and the p-type cladding layer 126 are formed by epitaxial growth, and the lamination of these is referred to as a laser multilayer structure 120. Note that the multi-beam semiconductor laser element 100A may include electrodes formed on the back surface of the substrate 110 and electrodes or contact layers formed on the upper side of the p-type cladding layer 126, but these are omitted in Figure 2.

[0051] The height h of the sum of the substrate 110 and the n-type cladding layer 122 (the lamination of these two layers is referred to as the base structure 132) of the stacked structure 130 is different in m (m≧2) regions A1 to A m adjacent in the first direction (x direction). In FIG. 2, for the purpose of simplifying the explanation and facilitating understanding, the case of m = 3 is described. Actually, another region may exist on the left side of the first region A1, and another region may exist on the right side of the third region A3.

[0052] For the i-th region A i , the thickness of the substrate 110 is denoted as t i , and the thickness of the n-type cladding layer 122 is denoted as d i . The height h i is the combined height of the thickness t i of the substrate 110 and the thickness d i of the n-type cladding layer 122. h i = t i + d i

[0053] In this embodiment, the thicknesses d1 to d3 of the n-type cladding layer 122 are substantially uniform, and the thicknesses t1 to t3 of the substrate 110 are non-uniform in the three regions A1 to A3. Specifically, the thickness t2 of the substrate 110 in the central second region A2 is larger than the thicknesses t1 and t3 of the substrate 110 in the first region A1 and the third region A3 sandwiching it, and thus the total height h2 is larger than h1 and h3.

[0054] In n (2≦n≦m) of the m regions, n laser resonators 140_1, 140_n of a ridge stripe structure extending in the second direction (y-axis direction in this embodiment) perpendicular to the first direction (x-axis direction in this embodiment) are formed. In this embodiment, n = 2, and laser resonators 140_1 and 140_2 are formed in the first region A1 and the third region A3.

[0055] If multiple laser resonators 140 are to be driven independently, it is necessary to electrically isolate the laser resonators 140_1 to 140_n. The multi-beam semiconductor laser element 100A is provided with isolation grooves 150 for electrical isolation between adjacent laser resonators 140_1 and 140_2. These isolation grooves 150 are formed in the second region A2 along the second direction (y-direction, plane of the depth direction). The isolation grooves 150 may be hollow, filled with an insulator, or have an insulating film formed on their surface.

[0056] The above describes the configuration of the multi-beam semiconductor laser element 100A. Next, I will explain the first advantage of the multi-beam semiconductor laser element 100A. The first advantage of the multi-beam semiconductor laser element 100A relates to the ease of manufacturing the multi-beam semiconductor laser element 100A.

[0057] The inventors of this invention have independently recognized that when a light-emitting layer is deposited on a substrate with varying heights, the crystal growth conditions, specifically the gas flow rate, and consequently the deposition rate and composition, are determined by the unevenness of the substrate structure.

[0058] In Example 1, a light-emitting layer 124 is deposited on a substrate structure 132 consisting of a substrate 110 with different thicknesses t1 to t3 for each region A1 to A3 and an n-type cladding layer 122. With this configuration, the crystal growth conditions for the light-emitting layer 124 differ for each region A1 to A3, resulting in the formation of light-emitting layers 124 with different thicknesses and compositions for each of the multiple regions A1 to A3. The thickness of the light-emitting layer 124 may refer not only to the total thickness of the light-emitting layer 124 but also to the thickness of the sublayers it contains, such as the guide layer and quantum well layer. By forming multiple laser resonators 140_1, 140_2 so as to include light-emitting layers 124 with different thicknesses and compositions, the oscillation wavelengths λ1 and λ2 of the multiple laser resonators 140_1, 140_2 can be easily made different.

[0059] Region A of the i-th element (i=1,2,...n) i The deposition rate in region A i Height h iIt will be affected by this.

[0060] Region A of the i-th element (i=1,2,...n) i The deposition rate in region A i width w i It will be affected by this.

[0061] Also, the i-th region A (i=1,2,...n) i The deposition rate in adjacent region A i-1 ,A i+1 It is also affected by the following. Specifically, area A i The deposition rate is in the adjacent region A i-1 ,A i+1 width w i-1 ,w i+1 It is affected by region A. i The deposition rate in the region adjacent to the right is region A. i+1 The difference in elevation between Δh and Δh i+ =h i -h i+1 Influenced by, similarly, the adjacent region A to the left i-1 The difference in elevation between Δh and Δh i- =h i -h i-1 It is also affected by this.

[0062] In summary, Region A i The oscillation wavelength when a laser resonator 140 is formed is (i) Area A i Height h i (ii) Area A i width w i (iii) Adjacent region A i+1 , A i-1 Height h i+1 ,h i-1 (iv) Adjacent region A i+1 , A i-1 width w i+1 ,w i-1 It can be said that this is determined by the combination of these factors. Therefore, by designing the height and width of multiple regions of the base structure 132 as design parameters, it is possible to form multiple laser resonators 140 with different oscillation wavelengths.

[0063] Next, I will explain the second advantage of the multi-beam semiconductor laser element 100A. The second advantage concerns heat dissipation (cooling) of the multi-beam semiconductor laser element 100A.

[0064] Figure 3 illustrates the heat dissipation of the multi-beam semiconductor laser element 100A shown in Figure 2. When the laser resonators 140_1 and 140_2 oscillate, they generate heat primarily from the light-emitting layer 124 and the p-type cladding layer 126. The heat generated in the light-emitting layer 124 of the first region A1 and the heat generated in the light-emitting layer 124 of the third region A3 diffuse into the surroundings. In the multi-beam semiconductor laser element 100A shown in Figure 2, there are protrusions 112 of the substrate 110 next to the light-emitting layers 124 of the first region A1 and the third region A3. Since the thermal conductivity of the substrate 110 is greater than that of the separation groove 150, the heat H1 and H2 from the light-emitting layers 124 are not blocked by the separation groove 150 and are dissipated via the protrusions 112 of the substrate 110 in the second region A2. This is the second advantage.

[0065] To better enjoy the second advantage, it is preferable that the light-emitting layer 124 in the first region A1 and the light-emitting layer 124 in the third region A3 are located at a height lower than the surface height (i.e., t2) of the substrate 110 in the second region A2, as shown in Figure 2.

[0066] The advantages of the multi-beam semiconductor laser element 100A in terms of heat dissipation become clear when compared with comparative technologies.

[0067] Figure 4 illustrates the improvement in heat dissipation in the multi-beam semiconductor laser element 100A according to the embodiment. The upper part of Figure 4 shows a model in which a protrusion 112 of the substrate 110 is located next to the light-emitting layer 124 of the laser resonator 140, which is the heat source. The lower part of Figure 4 shows a model of a multi-beam semiconductor laser element according to the comparative technology. In the comparative technology, the substrate 110 is flat, and instead of the protrusion 112, adjacent channels are electrically (and optically) isolated by a separation groove 151 made of SiO2. The middle part of Figure 4 shows the simulation results with the distance from the heat source on the horizontal axis and the internal temperature on the vertical axis. x=0 is the position of the heat source, x1 is the position of the side wall of the protrusion 112 of the substrate 110 in the embodiment, and the position of the separation groove 151 in the comparative technology.

[0068] In the comparative technique, where separation grooves 151 are formed, the separation grooves 151 act as thermal resistance, causing the internal temperature in the region close to the heat source to be relatively higher. In contrast, in this embodiment, heat is efficiently dissipated through the protrusions 112 of the substrate 110, so the internal temperature in the region close to the heat source can be lowered compared to the comparative technique.

[0069] Next, I will explain the third advantage of the multi-beam semiconductor laser element 100A. The third advantage concerns the suppression of optical crosstalk between channels.

[0070] Returning to Figure 3, let's explain the suppression of optical crosstalk. In each of the laser resonators 140_1 and 140_2, the laser light is guided in the depth direction of the paper (y direction) and emitted as beam BM from the emitters 102_1 and 102_2. However, spontaneous emission or stray light L1 and L2, which includes a portion of the laser light, is also emitted in the transverse direction of the paper (x direction). If the substrate 110 is a semiconductor material with a band gap that absorbs the oscillation wavelength of the laser, the stray light L1 and L2 will be absorbed by the protrusions 112 of the substrate 110. Therefore, with the multi-beam semiconductor laser element 100A, optical crosstalk between adjacent laser resonators 140_1 and 140_2 can be suppressed.

[0071] The material of the substrate 110 is the oscillation wavelength λ1 to λ n GaAs is preferred when the wavelength is in the range of 580 to 900 nm. Also, the oscillation wavelength λ1 to λ n GaN is preferred when the wavelength is 360 nm or less.

[0072] The above describes the configuration and advantages of the multi-beam semiconductor laser element 100A. Next, we will explain its manufacturing method.

[0073] Figures 5(a) to 5(f) show the manufacturing method of the multi-beam semiconductor laser element 100A shown in Figure 2.

[0074] Figures 5(a) and (b) show the process of forming irregularities on a GaAs substrate (hereinafter also referred to as the GaAs substrate) 110. First, a film 200, which will serve as a mask when etching the GaAs substrate 110, is deposited on the GaAs substrate 110 and patterned in a stripe pattern according to the multibeam pitch. The film 200 can be made of, for example, SiO2. Figure 5(a) shows the film 200 after patterning. As an example, in the case of a 50 μm pitch, the patterning is done with a line and space (50 μm pitch) with a width of 25 μm. Using the film 200 as a mask, grooves 202 with a depth of, for example, 2 μm are formed on the substrate 110. After the formation of the grooves 202, the SiO2 layer of film 200 is removed with a hydrofluoric acid-based solution and the surface is cleaned.

[0075] Refer to Figure 5(c). A laser multilayer structure 120 is epitaxially grown on a grooved GaAs substrate 110 using the MOCVD method (Metal Organic Chemical Vapor Deposition). A typical multilayer structure includes an n-type cladding layer 122, an emissive layer 124 (also called an optical waveguide core layer) containing a guide layer and a quantum well layer, a p-type cladding layer 126, and a p-type contact layer 128. Each layer can be further subdivided according to its composition and doping concentration. As an example, the composition of the n-type cladding layer 122 is (Al x Ga 1-x ) 1-y In yAt P, x=1, y=0.5. In order to match the lattice with the GaAs substrate 110, the In composition y is adjusted to 0.5 in this embodiment. The composition ratio of Al to Ga x:1-x is such that x is larger, and x:1-x=1:0 is also acceptable. Following the n-type cladding layer 122, a lower guide layer, a quantum well and barrier layer, and an upper guide layer are deposited to form the light-emitting layer 124. The guide layer is sometimes called the SCH layer or confinement layer, and has a higher refractive index than the cladding layers 122 and 126, and a lower refractive index than the quantum well layer. Therefore, the Al composition ratio x is highest in the cladding layers 122 and 126, and the amount of raw material supplied is adjusted so that it decreases in the order of guide layer or barrier layer, and then quantum well layer. In particular, the Al composition ratio x is small in the quantum well layer, and in this embodiment, the composition of the guide layer and barrier layer was set to x=0.7, y=0.5. The quantum well layer will be described as GaInP(x=0). These guide layer, barrier layer, and quantum well layer function as core layers in the optical waveguide through which the laser light propagates. The thickness of the core layer depends on the wavelength and the refractive index of each layer, but for a red laser it is approximately 50 nm to 500 nm, and in this embodiment it is approximately 100 nm in total. Furthermore, a p-type cladding layer 126 is deposited, and then p-type GaAs is deposited as a p-type contact layer 128 (also called a cap layer). As an example, the thickness of the p-type cladding layer 126 can be 1700 nm, and the thickness of the p-type contact layer 128 can be 300 nm.

[0076] As shown in Figure 5(c), the laminated structure 130 has recesses 204 and protrusions 206 based on the irregularities of the GaAs substrate 110.

[0077] Next, as shown in Figure 5(d), a laser resonator (laser structure) 140 having a ridge-stripe structure is formed in the recess 204 of the laminated structure 130.

[0078] Specifically, a ridge structure is formed by partially removing the p-type contact layer 128 and the p-type cladding layer 126 using photolithography and etching techniques. Note that when forming the ridge structure on each p-type cladding layer 126, a bank structure may also be formed on each p-type cladding layer 126. Each bank can be provided on both sides of each ridge structure.

[0079] If it is desired that multiple laser resonators 140 be controlled independently, isolation grooves 150 are formed. In this embodiment, electrical isolation can be ensured by forming grooves in the protrusions 206 that do not have emitters (laser resonators 140). By forming isolation grooves 150 in the protrusions 206, the isolation grooves 150 do not hinder the heat from the laser resonators 140 from being dissipated through the substrate 110 of the protrusions 206, thereby maintaining heat dissipation.

[0080] Next, as shown in Figure 5(e), an insulating film 134 made of an SiO2 film or the like is formed on the surfaces of the ridge structure and bank structure by a method such as plasma CVD.

[0081] Next, as shown in Figure 5(f), the insulating film 134 is patterned using photolithography and dry etching techniques to form openings in the insulating film 134 that expose the upper surfaces of each ridge structure. Then, electrode material made of a metal such as Au is formed on the openings and the insulating film 134 using methods such as sputtering or vapor deposition. Furthermore, the electrode material on the insulating film 134 is patterned using photolithography and dry etching techniques to form electrodes 138 connected to each ridge structure through each opening on the insulating film 134. Electrodes 139 are also formed on the back side of the substrate 110. Furthermore, the semiconductor substrate on which the electrodes 138 are formed is cleaved into a bar shape. Then, an end-face protective film is deposited on the cleaved surface, which will be the end face of the bar, using methods such as sputtering. By separating the bar on which the end-face protective film is formed on the cleaved surface into individual pieces, the multi-beam semiconductor laser element 100A is completed.

[0082] The above describes the manufacturing method for the multi-beam semiconductor laser element 100A. As shown in Figure 5(c), when the laser multilayer structure 120 is deposited on a grooved, or in other words, uneven, GaAs substrate 110, the gas flow rate in MOCVD changes locally depending on the height and width of the grooves (regions A1 to A3 in Figure 2), and the deposition rate can be varied depending on the height and width of the grooves. By actively utilizing this effect, it is possible to introduce intentional errors in the thickness and composition of the light-emitting layer 124 in each region, thereby realizing a multi-beam semiconductor laser with different wavelengths between beams.

[0083] Furthermore, localized changes in the film deposition rate are more pronounced the narrower the width of the uneven surface; therefore, to equalize the film deposition rate, the width of the uneven surface should be increased.

[0084] In this manufacturing method, it is not necessary to perform epitaxial growth in multiple steps to create a multi-beam laser with multiple wavelengths; epitaxial growth can be performed only once. This makes it possible to manufacture multi-beam semiconductor lasers with different wavelengths between beams at a low cost.

[0085] (Example 2) Figure 6 is a cross-sectional view of the multi-beam semiconductor laser element 100B according to Example 2. The structure of the multi-beam semiconductor laser element 100B will be explained, focusing on the differences from the multi-beam semiconductor laser element 100A of Example 1 (Figure 2).

[0086] The multi-beam semiconductor laser element 100B, like the multi-beam semiconductor laser element 100A, has a layered structure 130 with irregularities, and the layered structure 130 has different heights for each of the multiple regions A1 to A3 of the underlying structure 132.

[0087] In Example 2, n=3, and in addition to the first region A1 and the third region A3, a laser resonator 140_3 is also formed in the second region A2.

[0088] In order to enable independent control of the laser resonators 140_1 to 140_3, it is necessary to electrically isolate adjacent laser resonators 140. For this purpose, isolation grooves 150_1 and 150_2 are formed between laser resonators 140_1 and 140_3, and between laser resonators 140_2 and 140_3. The isolation grooves 150_1 and 150_2 are preferably formed in the second region A2 corresponding to the protrusion. By forming the isolation grooves 150_1 and 150_2 in the protrusion, heat from the laser resonators 140_1 and 140_2 is dissipated through the substrate 110 of the protrusion 206 without being obstructed by the isolation grooves 150_1 and 150_2.

[0089] Furthermore, the laser resonator 140_3 formed in the convex second region A2 lacks a substrate 110 on the side of the light-emitting layer 124 and is sandwiched between separation grooves 150_1 and 150_2, which have low thermal conductivity. Therefore, the heat dissipation conditions are equivalent to those of the comparative technique described with reference to Figure 4, and are at a disadvantage compared to the laser resonators 140_1 and 140_2 formed in the concave areas. However, this seemingly disadvantageous point has the effect of suppressing output variations between multiple beams, as will be explained below.

[0090] As described above, the gas flow velocity within the MOCVD is locally changed by the height and width of regions A1 to A3, and the film deposition rate can be varied depending on the height and width of the grooves. As a result, the oscillation wavelength λ3 of the laser resonator 140_3 formed in the second region A2 is longer than the oscillation wavelengths λ1 and λ2 of the laser resonators 140_1 and 140_2 formed in the first region A1 and third region A3, respectively. For example, if λ1 and λ2 are approximately 640 nm, λ3 can be set to 645 nm.

[0091] Here, the degree of decrease in beam output due to temperature rise is more pronounced the shorter the oscillation wavelength. If the temperature rise of the multiple laser resonators 140_1 to 140_3 were uniform, the output of the long-wavelength laser resonator 140_3 would be greater than the output of the short-wavelength laser resonators 140_1 and 140_2, resulting in output variations between the beams. In contrast, in the multi-beam semiconductor laser element 100B according to Example 2, the temperature rise of the long-wavelength laser resonator 140_3 is greater than the temperature rise of the short-wavelength laser resonators 140_1 and 140_2, thus enabling the output of the three beams to be made uniform.

[0092] Next, a method for manufacturing the multi-beam semiconductor laser element 100B according to Example 2 will be described.

[0093] Figures 7(a) to 7(d) show the manufacturing method of the multi-beam semiconductor laser element 100B shown in Figure 6. Figure 7(a) shows a stacked structure 130 having recesses 204 and protrusions 206. The manufacturing process of the stacked structure 130 is the same as in Example 1 and has been explained with reference to Figures 5(a) to 5(c).

[0094] In Example 2, since a laser resonator is also formed on the protrusion 206, the line and spacing of the grooves in the GaAs substrate 110 may differ from that in Example 1. For example, in the case of a 50 μm pitch, patterning can be done with a line and spacing of 50 μm width (100 μm pitch).

[0095] Next, as shown in Figure 7(b), a laser resonator 140 is formed in the recess 204 and the protrusion 206 by the same process as in Example 1 (Figure 5(d)). Subsequently, as shown in Figures 7(c) and (d), an insulating film 134 and electrodes 138 and 139 are formed.

[0096] The above describes the manufacturing method for the multi-beam semiconductor laser element 100B. According to this manufacturing method, similar to Example 1, the light-emitting layer 124 is grown at different deposition rates in each region, making it easy to create different oscillation wavelengths.

[0097] (Example 3) Figure 8 is a cross-sectional view of a multi-beam semiconductor laser element 100C according to Example 3. Similar to Example 1, Example 3 includes a substrate structure 132C having irregularities, but the structure of the substrate structure 132C differs from that of Example 1. Specifically, in Example 3, the substrate structure 132C consists of an n-type cladding layer 122 with different thicknesses d1 to d3 for each region A1 to A3, formed on a substantially flat substrate 110. Other aspects are the same as in Example 1.

[0098] The method for forming the n-type cladding layer 122 with different thicknesses in each region is not particularly limited. For example, the n-type cladding layer 122 may be formed with the same thickness throughout the entire region, and then the n-type cladding layer 122 may be selectively etched to different depths in each region. Alternatively, the n-type cladding layer 122 may be selectively grown to have different thicknesses in each region.

[0099] According to Example 3, when the light-emitting layer 124 is epitaxially grown, the deposition rate differs for each region A1 to A3 due to the unevenness of the underlying substrate structure 132C. This makes it possible to generate multiple beams with different wavelengths.

[0100] In Example 3, there is no protrusion on the substrate 110 on the side of the recessed laser resonator 140, which is disadvantageous from the viewpoint of heat dissipation compared to Example 1. However, since there is no heat blocking by the separation groove 150, it is advantageous from the viewpoint of heat dissipation compared to the comparative technique shown in Figure 4, i.e., the structure in which the substrate 110 is flat and a separation groove 151 made of SiO2 is formed instead of the protrusion 112.

[0101] In the multi-beam semiconductor laser element 100C shown in Figure 8, a laser resonator 140 may also be formed in the second region A2, which is a convex portion, similar to Example 2.

[0102] (modified version) The embodiments and examples described above are illustrative, and it will be understood by those skilled in the art that various modifications are possible in combinations of their components and processing steps. Such modifications will be described below.

[0103] (Variation 1) The cross-sectional shape of the base structure 132 and the arrangement of the laser resonator 140 are not limited to those described in the embodiment. As described above, any region A i The oscillation wavelength when the laser resonator 140 is formed is determined by the following combination of design parameters (i) to (iv). (i) Area A i Height h i (ii) Area A i width w i (iii) Adjacent region A i+1 , A i-1 Height h i+1 ,h i-1 (iv) Adjacent region A i+1 , A i-1 width w i+1 ,w i-1 Therefore, among the multiple regions, region A that forms the laser resonator 140 is such that at least one of the parameters (i) to (iv) is different. i , A j You should choose that.

[0104] Figures 9(a) to 9(g) are simplified cross-sectional views of a modified multi-beam semiconductor laser element 100. Figures 9(a) to 9(g) schematically show the cross-sectional shape of the base structure 132 and the arrangement of the laser resonator 140.

[0105] Figure 9(a) shows an example with different parameter (i). In the multi-beam semiconductor laser element 100a in Figure 9(a), m=5 and n=2, and five regions A1 to A5 and two laser resonators 140_1 and 140_2 are shown. The regions A1 and A3 where the laser resonators 140_1 and 140_2 are formed have different heights h1 and h3.

[0106] Figure 9(b) shows an example with different parameters (ii). In the multi-beam semiconductor laser element 100b in Figure 9(b), m=5 and n=2, and five regions A1 to A5 and two laser resonators 140_1 and 140_2 are shown. The regions A1 and A3 where the laser resonators 140_1 and 140_2 are formed have different widths w1 and w3.

[0107] Figure 9(c) shows an example with different parameters (i) and (ii). In the multi-beam semiconductor laser element 100c in Figure 9(c), m=3 and n=2, and three regions A1 to A3 and two laser resonators 140_1 and 140_2 are shown. Regions A2 and A3, where the laser resonators 140_1 and 140_2 are formed, have different heights h2 and h3 and widths w2 and w3.

[0108] Figure 9(d) shows an example with different parameters (i). In the multi-beam semiconductor laser element 100d in Figure 9(d), m=3 and n=3, and three regions A1 to A3 and three laser resonators 140_1 to 140_3 are shown. The regions A1 to A3 in which the laser resonators 140_1 to 140_3 are formed have different heights h1, h2, and h3. In Figure 9(d), the widths w1 to w3 of multiple regions A1 to A3 are the same, but the widths w1 to w3 of multiple regions A1 to A3, i.e., the parameter (ii), may also be different.

[0109] Figure 9(e) shows an example with different parameters (iii). In the multi-beam semiconductor laser element 100e, m=6 and n=2, and six regions A1 to A6 and two laser resonators 140_1 to 140_2 are shown. Laser resonators 140_1 and 140_2 are formed in regions A2 and A4. In regions A2 and A4, heights h2 and h4 are equal, and widths w2 and w4 are also equal.

[0110] Focusing on region A2, the elevation difference Δh between region A2 and region A1 is 2- The value is negative, and the height difference Δh between region A2 and region A3 is negative. 2+ This is true. Focusing on region A4, the difference in elevation between region A4 and region A3 is Δh. 4-The value is positive, and the height difference Δh between region A4 and region A5 is positive. 4+ This is positive. Therefore, it can be said that parameter (iii) is different in regions A2 and A4.

[0111] Figure 9(f) is another example with different parameters (iii). In the multi-beam semiconductor laser element 100f, m=5 and n=2, and five regions A1 to A5 and two laser resonators 140_1 to 140_2 are shown. Focusing on region A2, the height difference Δh 2- Δh 2+ All of these are positive, and focusing on region A4, the elevation difference Δh 4- Δh 4+ Both are positive, but Δh 2- Δh 2+ The set and Δh 4- Δh 4+ The pairs have different values. Therefore, it can be said that parameter (iii) is different in regions A2 and A4.

[0112] Figure 9(g) shows an example with different parameters (iv). In the multi-beam semiconductor laser element 100g in Figure 9(g), m=5 and n=2, and five regions A1 to A5 and two laser resonators 140_1 and 140_2 are shown. Regions A1 and A3, where laser resonators 140_1 and 140_2 are formed, have equal heights and equal widths. The difference in deposition rates between region A1 and region A3 is introduced by the difference in width w4 between region A4 adjacent to the left of region A1 and region w5 between region A3 and region A5 adjacent to the right.

[0113] Those skilled in the art will understand that there are various modifications to the cross-sectional shape of the substrate structure 132 and the arrangement of the laser resonator 140 that are not illustrated herein, and these modifications are also included in the scope of this disclosure and the invention.

[0114] (Modification 2) Regarding the multi-beam semiconductor laser element 100A according to Example 1, it was explained that the light leaking from the recessed laser resonator 140 is shielded by the protruding substrate 110. This shielding function may be realized by a material other than the protruding substrate 110.

[0115] Figure 10 is a cross-sectional view of a multi-beam semiconductor laser element 100D according to Modification 2. The multi-beam semiconductor laser element 100D includes a light-shielding member 152 positioned between adjacent laser resonators 140_1 and 140_2. The light-shielding member 152 can be made of a semiconductor or metal that absorbs light of the oscillation wavelength of the laser resonator 140. The lower end of the light-shielding member 152 preferably reaches at least the lower end of the light-emitting layer 124 in order to suppress optical crosstalk between the two laser resonators 140_1 and 140_2. In this Modification 2, the lower end of the light-shielding member 152 penetrates the n-type cladding layer 122 and is formed to the upper surface of the protrusion 112.

[0116] As shown in Figure 10, the light-shielding member 152 is particularly effective when the substrate 110 has small irregularities and the leaked light from adjacent laser resonators 140_1 and 140_2 is not absorbed by the protrusions 112 of the substrate 110.

[0117] (Variation 3) In Examples 1 to 3, if independent driving of the multiple laser resonators 140 is not required, the separation groove 150 may be omitted.

[0118] (Modification 4) The embodiments and some examples and modifications described so far have focused on multi-wavelength beams, but multi-wavelength beams are not essential in this disclosure, and cases where all beams have the same wavelength can also be included in the scope of this disclosure or the present invention. For example, in Figure 2 (Example 1), when w1=w3 and h1=h3, λ1=λ2. Alternatively, even when w1≠w3 and h1≠h3, if w1 and w3 are sufficiently large, λ1≈λ2 may be possible. In this case, the first advantage described with respect to Example 1 is lost, but at least one of the second, third, and fourth advantages is still achieved, resulting in a superior effect compared to the prior art.

[0119] The embodiments merely illustrate the principles and applications of the present invention, and many modifications and changes in arrangement are permitted in the embodiments, without departing from the spirit of the present invention as defined in the claims. [Explanation of symbols]

[0120] 100...Multibeam semiconductor laser element, 102...Emitter, 110...Substrate, 120...Laser multilayer structure, 122...n-type cladding layer, 124...Light-emitting layer, 126...p-type cladding layer, 130...Laminated structure, 132...Underlying structure, 134...Insulating film, 138...Electrode, 139...Electrode, 140...Laser resonator, A1, A2, A m ...area, 150...separation groove, 152...light-shielding member.

Claims

1. A multi-beam semiconductor laser element with end-face emission, The device comprises a laminated structure including a substrate, a first conductive cladding layer, an emissive layer, and a second conductive cladding layer. In the aforementioned laminated structure, the combined height of the substrate and the first conductive cladding layer differs for each m (m≧2) adjacent region in the first direction. Of the m regions, n (2 ≤ n ≤ m) have n laser resonators formed in a ridge-stripe structure extending in a second direction perpendicular to the first direction, at least two of the n laser resonators have different oscillation wavelengths, and the thickness of the substrate differs for each of the m regions. The substrate includes GaAs when the oscillation wavelength of the laser resonator is in the range of 580 to 900 nm, and includes GaN when the oscillation wavelength is 360 nm or less. The n regions include adjacent first, second, and third regions, and the thickness of the substrate in the second region is greater than the thickness of the substrates in the first and third regions. The light-emitting layer in the first region and the light-emitting layer in the third region are located at a height lower than the surface of the substrate in the second region. A multi-beam semiconductor laser element characterized in that the oscillation wavelength of the laser resonator in the second region is longer than the oscillation wavelengths of the laser resonators in the first and third regions, respectively.

2. The multibeam semiconductor laser element according to claim 1, characterized in that a separation groove extending in the second direction is further formed in the second region.

3. The multi-beam semiconductor laser element according to claim 1, characterized in that a semiconductor or metal that absorbs light of the oscillation wavelength of the laser resonator is placed between adjacent laser resonators.

4. A method for manufacturing an end-face emitting type multibeam semiconductor laser element according to claim 1, A step of forming a substrate structure including a substrate and a first conductive cladding layer, wherein the thickness of the substrate structure is different for each m (m≧2) adjacent regions in the first direction, The steps include forming a light-emitting layer and a second conductive cladding layer on the aforementioned base structure, The steps include forming n laser resonators with a ridge-stripe structure extending in a second direction perpendicular to the first direction in n of the m regions (2 ≤ n ≤ m), A manufacturing method characterized by comprising the following:

5. The step of forming the aforementioned base structure is: The steps include forming a groove in the substrate that extends in the second direction, The steps include forming the first conductive cladding layer on the substrate on which the grooves are formed, The manufacturing method according to claim 4, characterized by including the following:

6. The manufacturing method according to claim 5, characterized in that the step of forming the grooves includes the step of forming a plurality of grooves of different widths.

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