JP2004207646A - Semiconductor laser element and semiconductor laser array - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor laser array beam source capable of providing a high power with high light condensing. <P>SOLUTION: The semiconductor laser element 1 has a first conductivity clad layer 13, a second conductivity clad layer 17, and a quantum well active layer 15 sandwitched by the layer 13 and the layer 17. A plurality of second conductivity semiconductor regions 21 having a refractive index smaller than that of the layer 17 for laser light and a depth which does not reach the layer 15 are arranged in the layer 17 at predetermined intervals. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a semiconductor laser device and a semiconductor laser array.
[0002]
[Prior art]
In recent years, semiconductor lasers have been required to have higher output and higher condensing density. Conventionally, as a semiconductor laser device capable of obtaining a high output, for example, a semiconductor laser device having a broad area structure having a gain waveguide as disclosed in Patent Document 1 has been used in many cases. Usually, a semiconductor laser device having this structure is designed to have a current injection region width (light emitting region width) of about 100 to 200 μm, and oscillates in a multi-space lateral mode.
[0003]
[Patent Document 1]
JP 2001-257417 A
[Problems to be solved by the invention]
However, although the semiconductor laser device having the gain waveguide structure can obtain a high output, it oscillates in a multi-spatial transverse mode and generates an uneven heat distribution in the light emitting region. In FIG. 7, the far-field image of the horizontal component with respect to the active layer has a shape in which the center portion is low at both ends and high at both ends, and has peaks at both ends (see FIG. 7A). Such a laser beam has a low coupling efficiency with the lens, and it is difficult to shape the light by the lens, so that the light condensing area becomes large and a high light condensing density cannot be obtained.
[0005]
On the other hand, in order to increase the coupling efficiency with the lens and reduce the focusing area, the far-field image of the laser beam emitted from the emission region should be close to a unimodal Gaussian shape (see FIG. 7B). is necessary. However, in order to obtain such a single-peak far-field image light from a semiconductor laser, it is necessary to oscillate in a spatial transverse single mode, and thus it is difficult to obtain high output light in terms of structure.
[0006]
Thus, it has been difficult to obtain a high light density and a high output using the conventional semiconductor laser device as a light source.
[0007]
Therefore, an object of the present invention is to provide a semiconductor laser device and a semiconductor laser array which can solve the above problems and can obtain a high light-condensing density and a high output.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, a semiconductor laser device according to the present invention is provided with a first conductivity type clad layer, a second conductivity type clad layer, and a first conductivity type clad layer and a second conductivity type clad layer. A semiconductor laser device having a quantum well active layer, wherein the first conductivity type cladding layer has a lower refractive index to laser light than the first conductivity type cladding layer and has a depth not reaching the quantum well active layer. A plurality of second conductivity type semiconductor regions having the same are arranged at predetermined intervals.
[0009]
According to the present semiconductor laser device, since the second conductivity type semiconductor layers are arranged in the first conductivity type cladding layer at a predetermined interval, a pair of adjacent second conductivity type semiconductor regions and the second conductivity type semiconductor region are formed. The refractive index waveguide structure is formed by the first conductive type clad layer located between the conductive type semiconductor regions. Therefore, the generated laser light can be confined in the region of the quantum well active layer corresponding to the first conductivity type cladding layer located between the second conductivity type semiconductor regions. Therefore, the generated laser beams can be prevented from being phase-coupled to each other, so that the arrangement interval of the second conductive semiconductor layers can be narrowed, and high-power laser beams can be obtained.
[0010]
Further, in the above-mentioned semiconductor laser device, each region of the quantum well active layer corresponding to the region of the first conductivity type cladding layer between the adjacent second conductivity type semiconductor regions has a laser beam generated by spatial lateral single mode oscillation. It may be characterized in that it is a region in which is generated.
[0011]
The present semiconductor laser device can emit laser light having a unimodal far-field image because of spatial transverse single mode oscillation. Since the plurality of laser beams are generated and emitted in each region arranged in the semiconductor laser device, the semiconductor laser device as a whole can emit a laser beam having a unimodal far-field image. A laser beam having a unimodal far-field pattern has high coupling efficiency with the lens, so that parallelization can be performed with high accuracy, and a high light-condensing density can be obtained.
[0012]
The semiconductor laser array of the present invention is characterized in that a plurality of the semiconductor laser elements are arranged in the same direction as the arrangement direction of the second conductivity type semiconductor regions.
[0013]
Further, the semiconductor laser array of the present invention is a semiconductor laser array in which a plurality of semiconductor laser elements are arranged in an array, and the semiconductor laser element has a refractive index waveguide structure and is driven by spatial transverse single mode oscillation. A plurality of semiconductor laser units that emit light are provided, and the semiconductor laser units are arranged in the same direction as the arrangement direction of the semiconductor laser elements.
[0014]
According to the semiconductor laser array, each of the semiconductor laser units in the semiconductor laser element oscillates in the spatial lateral single mode, so that a laser beam having a unimodal far-field image can be emitted. Since the plurality of emission regions are arranged in the semiconductor laser device, the semiconductor laser device as a whole can emit laser light having a unimodal far-field pattern. In addition, high output can be obtained by arranging a plurality of such semiconductor laser units.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the same reference numerals are used for the same elements, and duplicate descriptions are omitted.
[0016]
The semiconductor laser array 1 according to the present embodiment emits laser light in a wavelength band of 940 nm, and has a plurality of semiconductor laser elements 3 arranged in a one-dimensional direction as shown in FIG. The semiconductor laser device 3 includes one emission region 5, and the emission region 5 emits laser light substantially perpendicular to the arrangement direction of the semiconductor laser devices 3. The emission region 5 is a collective region in which a plurality of emission regions 5a are arranged in the same direction as the arrangement direction of the semiconductor laser elements 3, and each of the emission regions 5a emits laser light. Hereinafter, the direction in which the semiconductor laser elements 3 are arranged in an array as shown in FIG. 1 will be referred to as an x direction, the direction of laser light emission will be referred to as a z direction, and a direction perpendicular to both the x direction and the z direction will be referred to as a y direction. I do. FIG. 2 is a cross-sectional view of a portion corresponding to the emission region 5 of the semiconductor laser device 3 in which a plane including both the x direction and the y direction is a cut surface.
[0017]
As shown in FIG. 2, the semiconductor laser device 3 includes an n-type cladding layer 13 (second conductivity type cladding layer), a quantum well active layer 15, and a p-type cladding layer 17 (first conductivity type cladding layer) on a substrate 11. , And the cap layer 19 are laminated in the y direction. In the present embodiment, the substrate 11 is made of n-GaAs and has a thickness in the y direction of about 100 μm. The quantum well active layer 15 is made of GaInAs / AlGaAs and has a thickness of about 0.1 μm in the y direction. The n-type cladding layer 13 is made of n-AlGaAs and has a thickness of about 2 μm in the y direction. The p-type cladding layer 17 is made of p-AlGaAs and has a thickness of about 2 μm in the y direction. The cap layer 19 is made of p-type GaAs and has a thickness of about 0.1 μm in the y direction.
[0018]
A plurality of block regions 21 (second conductivity type semiconductor regions) are provided so as to penetrate the cap layer 19 and extend into the p-type cladding layer 17 and are arranged at regular intervals in the x direction. The depth of the block region 21 in the y direction does not penetrate the p-type cladding layer 17 and is smaller than the depth reaching the quantum well active layer 15, and the block region 21 does not reach the quantum well active layer 15. The block region 21 has a structure in which a first block layer 21a and a second block layer 21b are stacked in the y direction. In the present embodiment, the width of the block region 21 in the x direction is about 10 μm and the thickness in the y direction is about 2.0 μm, and ten block regions are arranged in the x direction at a constant interval of about 15 μm. The first block layer 21a is made of n-AlGaAs and has a thickness of about 1.8 μm in the y direction. The second block layer 21b is made of n-GaAs and has a thickness of about 0.2 μm in the y direction.
[0019]
The p-electrode 23 is provided on the upper layer of the cap layer 19, and the n-electrode 25 is provided on the side opposite to the p-electrode 23, so that a current can be supplied to the semiconductor laser device 3.
[0020]
As described above, inside the p-type cladding layer 17, the block regions 21 of about 10 μm in the x direction and the regions of the p-type cladding layer 17 of about 5 μm sandwiched between the block regions 21 are alternately arranged. Assuming that one area divided by the block area 21 is a semiconductor laser unit 3a, the semiconductor laser element 3 has a plurality of semiconductor laser units 3a arranged in the x direction at substantially equal intervals.
[0021]
In the semiconductor laser unit 3 a, a region adjacent to the region of the p-type cladding layer 17 sandwiched between the block regions 21 in the quantum well active layer 15 in the z direction passes through the p-electrode 23 and the n-electrode 25. The region functions as a generation region that generates laser light when the current is injected, and an end surface in the z direction of the region functions as an emission region 5a that emits laser light. As described above, an aggregate in which the emission regions 5a are arranged in the x direction becomes the emission region 5 of the semiconductor laser device 3 shown in FIG.
[0022]
The first block layer 21a (made of n-AlGaAs) has a lower refractive index to laser light by making the Al composition higher than that of the surrounding p-type cladding layer 17 (made of p-AlGaAs). Further, each semiconductor laser unit 3a oscillates in a spatial lateral single mode in consideration of the material of each layer (p-type cladding layer 17, quantum well active layer 15, n-type cladding layer 13), width and depth of block region 21, and the like. It is designed to be.
[0023]
Next, a method of manufacturing the semiconductor laser array will be described with reference to FIG. First, an n-type AlGaAs n-type cladding layer 13, a GaInAs / AlGaAs quantum well active layer 15, a p-type AlGaAs p-type cladding layer 17, and a p-type GaAs cap layer 19 are epitaxially grown on an n-type GaAs substrate 11. (See FIG. 3A).
[0024]
Thereafter, a SiN film 27 is coated, and a resist stripe having a stripe width of 15 μm and a width of 5 μm is formed thereon by photowork. After removing the portion of the SiN film 27 where the resist is not attached, the cap layer 19 and the p-type clad layer 17 are etched. At this time, the etching is stopped before the p-type cladding layer 17 slightly remains and reaches the quantum well active layer 15 (see FIG. 3B).
[0025]
Next, n-type AlGaAs (first block layer 21a) and n-type GaAs (second block layer 21b) are crystal-grown in the concave portion formed by etching in the order of n-type AlGaAs (first block layer 21a) by selective crystal growth. The second block layer 21b is formed. Here, the first block layer 21a has a higher Al composition than the p-type cladding layer 17.
[0026]
Subsequently, the SiN film 27 is removed, and the p-electrode 23 is formed of Au, Pt, and Ti. Then, substrate polishing and chemical treatment are performed on the opposite surface side to form an n-electrode 25 of AuGe and Au (see FIG. 3C).
[0027]
The semiconductor laser device obtained as described above is cut out with an appropriate resonator length, and is coated with a reflective film. The semiconductor laser elements 3 thus manufactured are arranged in the x-direction and arrayed to manufacture the semiconductor laser array 1 (see FIG. 3D).
[0028]
According to the semiconductor laser array 1, since each semiconductor laser unit 3a oscillates in the spatial and transverse single mode, a laser beam having a unimodal (Gaussian) far-field image is emitted from each emission region 5a. It becomes. Since the far-field image is monomodal also with respect to the entire laser light in which a plurality of these laser lights are overlapped, a monomodal laser light is emitted as the entire emission region 5 of the semiconductor laser device. Laser light having such a unimodal far-field pattern has a high coupling efficiency with the lens. Therefore, when the semiconductor laser array 1 is mounted on the semiconductor laser device, the shaping and parallelization of the laser light by the collimating lens can be performed with high accuracy, and a high light-condensing density can be obtained. Further, since a plurality of semiconductor laser units 3a are arranged in the emission region 5 at narrow intervals, high output can be obtained. Therefore, according to the semiconductor laser array, the light-collecting area can be reduced and a high light-collecting density can be obtained.
[0029]
In the semiconductor laser array 1, since the depth of the block region 21 in the y direction is set so as not to reach the quantum well active layer 15, when the space of the block region is formed, the etching is performed on the quantum well active layer. It will stop shortly before reaching 5. Therefore, the etchant does not reach the quantum well active layer 15 and damage to the quantum well active layer 15 by the etchant can be prevented, and the laser light emitting layer can be kept in a good crystalline state.
[0030]
In the semiconductor laser array 1, the refractive index of the first block layer 21a in each semiconductor laser unit is made lower by making the Al composition higher than that of the surrounding p-type cladding layer 17. That is, the region other than the region corresponding to the block region 21 of the p-type cladding layer 17 has a structure (refractive index waveguide structure) having a relatively higher refractive index than the surroundings. For this reason, the laser light generated in the generation region corresponding to each emission region 5a is confined in the region (the emission region 5a) of the quantum well active layer 15 other than the region corresponding to the block region 21 due to the influence of the refractive index difference. It becomes.
[0031]
As described above, since the laser light is confined in each emission region in the x direction, phase coupling of light hardly occurs between the adjacent emission regions 5a, and stable laser light can be obtained. In addition, since phase coupling of light between adjacent emission regions is unlikely to occur, stable laser light can be obtained even when the interval between semiconductor laser units in the semiconductor laser element is further reduced. Therefore, the number and density of the emission regions 5a in the semiconductor laser element 5 can be increased, and it is easy to obtain a higher output.
[0032]
A far-field image obtained from one emission region 5 (one semiconductor laser element) of the semiconductor laser array 1 of the present embodiment was measured. FIG. 4A shows the measured far-field image. For comparison, a far-field image obtained from one emission region 5 of a conventional semiconductor laser array (having a broad area structure) was also measured. FIG. 4B shows a far-field image of the measured conventional semiconductor laser array. 4A and 4B, the characteristic Sh represents a far-field image in the horizontal direction (x direction), and the characteristic Sv represents a far-field image in the vertical direction (y direction). Regarding the horizontal direction (x-direction) component of the far-field image, the far-field image of the semiconductor laser array 1 of the present embodiment has a unimodal distribution, and is closer to a Gaussian shape than the conventional one. Therefore, when the semiconductor laser array 1 is mounted on a semiconductor laser device, the shaping and parallelization of the laser beam by the collimating lens can be performed with high accuracy, and a high light-condensing density can be obtained.
[0033]
Light collection was attempted using the semiconductor laser array 1 of the present embodiment as a light source and a semiconductor laser device having the configuration shown in FIG. The plurality of laser beams emitted from the emission region 5 of the semiconductor laser array 1 are parallelized in the y direction by the first collimating lens 40, and further parallelized in the x direction by the second collimating lens 50. The collimated light beam is further condensed by the condensing lens 60, and the intensity profile of the laser light collected on the spot 70 is shown in FIG. FIG. 6A shows the light intensity distribution in the horizontal direction (x direction), and FIG. 6B shows the light intensity distribution in the vertical direction (y direction). The size of the obtained condensed spot 70 was 259 μm in the horizontal direction and 302 μm in the vertical direction at full width at half maximum, and the output of the semiconductor laser array at this time was 60 W. As a result, the condensing density of 1.40 · 10 ⁵ w / cm was obtained. Is obtained.
[0034]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a semiconductor laser element and a semiconductor laser array that can obtain a high light-condensing density and a high output.
[Brief description of the drawings]
FIG. 1 is a perspective view of a semiconductor laser array according to an embodiment.
FIG. 2 is a sectional view of an emission region of the semiconductor laser array according to the embodiment.
FIG. 3 is a diagram illustrating a method for manufacturing the semiconductor laser array according to the embodiment.
FIG. 4A is a graph showing a far-field pattern of a laser beam emitted from the semiconductor laser device of the present embodiment. (B) is a graph showing a far-field pattern of laser light emitted from a conventional semiconductor laser device.
FIG. 5 is a configuration diagram of a semiconductor laser device using the semiconductor laser array of the present embodiment as a light source.
FIG. 6 is a graph of an intensity distribution of a condensed spot of a semiconductor laser device using the semiconductor laser array of the present embodiment as a light source.
FIG. 7A is a graph showing a far-field pattern of laser light emitted from a conventional semiconductor laser array. (B) is a graph showing a unimodal far-field image.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser array, 3 ... Semiconductor laser element, 3a ... Semiconductor laser unit, 5 ... Emission area, 5a ... Emission area, 11 ... Substrate, 13 ... N-type cladding layer, 15 ... Quantum well active layer, 17 ... P-type Cladding layer, 21a: first block layer, 21b: second block layer, 21: block region.

Claims (4)

A semiconductor laser device having a first conductivity type clad layer, a second conductivity type clad layer, and a quantum well active layer sandwiched between the first conductivity type clad layer and the second conductivity type clad layer,
In the first conductivity type cladding layer, a second conductivity type semiconductor region having a lower refractive index to laser light than the first conductivity type cladding layer and having a depth that does not reach the quantum well active layer has a predetermined distance. A plurality of semiconductor laser devices. Each region of the quantum well active layer corresponding to the region of the first conductivity type cladding layer between the adjacent second conductivity type semiconductor regions becomes a region for generating laser light generated by spatial lateral single mode oscillation. The semiconductor laser device according to claim 1, wherein: 3. A semiconductor laser array, wherein a plurality of the semiconductor laser elements according to claim 1 or 2 are arranged in the same direction as an arrangement direction of the second conductivity type semiconductor regions. A semiconductor laser element is a semiconductor laser array in which a plurality of semiconductor laser elements are arranged in an array,
The semiconductor laser element has a plurality of semiconductor laser units having a refractive index waveguide structure and emitting laser light by spatial transverse single mode oscillation,
A semiconductor laser array, wherein each of the semiconductor laser units is arranged in the same direction as the arrangement direction of the semiconductor laser elements.

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