JPH01175280A - Semiconductor laser array device - Google Patents

Abstract

PURPOSE:To make the far-field pattern of outgoing beams circular with no divergence, by arranging a reflecting plane facing an outgoing beam end plane, forming grating on the reflecting plane. CONSTITUTION:A laser beam outgoing end plane 10 perpendicular to a ridge waveguide is formed at a laser oscillating part A. The angle between a reflecting plane 11 and the outgoing beam end plane 10 is alpha and the line L intersected by these planes is parallel to the line intersected by the plane 10 and a laser junction plane. Gratings 30 are constructed by unevennesses on an Al film which are periodical in the vertical direction with respect to the line L intersected by plane 10 and the reflecting plane 11. When laser oscillation is caused by injecting electric current into the laser oscillating part A in the forward direction, a laser beam 45 is radiated from the outgoing beam end plane 10 to the reflecting plane 11. The beam 45 is converted into the parallel laser beam by the grating 30 mounted on the reflecting plane 11.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a semiconductor laser array device, and more particularly to a semiconductor laser array device that can obtain a circular far-field image.

(Prior Art) Semiconductor laser array devices that integrate multiple active waveguides of semiconductor lasers in parallel are capable of high-output operation, so they can be used, for example, as light sources for pumping solid-state lasers such as YAG lasers, and as light sources for spatial communication. , is currently being actively researched as a light source for optical recording systems. Among such semiconductor laser array devices, a phase-locked array device, in which guided light propagating through a waveguide is optically coupled to each other and has a certain phase relationship, uses a lens to convert the emitted light to the diffraction limit. It is extremely useful for applications, and is attracting attention.

As an example of this phase-locked array device, an example of a conventional phase-locked array device in which three ridge waveguides are integrated is shown in FIG. 5. This phase-locked array device was fabricated as follows. be done. First, LPE growth, MBE growth, M
By a crystal growth method such as OCVD growth, an n-Al>, Ga, -, As cladding layer 2 (thickness, 1.0 um>, p-AI, Ga, -, As active layer) is formed on an n-GaAs substrate 1. 3
(thickness, 0.08 μm), p-AI, Ga, -2As cladding layer 4 (thickness, 1.0 tt m), and p-GaA
s cap layer 5 (thickness, 1.0 μm) is sequentially grown (however, Al mixed crystal ratio X, L Z is x, z>y)0
Next, on top of that, a 3 μm thick
A resist pattern having three stripes of width at a period of 5 μm is formed. Thereafter, three ridges 6 are formed by an etching method such as reactive ion beam etching. An insulating film 7 is provided on the surface other than the ridge 6. A p-side electrode 8 is provided on the ridge 6, and an n-side electrode 9 is provided on the substrate 1. With such a configuration, current can be selectively passed only to the portion of the active layer 3 located below the ridge 6. Two emission end faces perpendicular to the resonator direction are formed by the open-leg method.

FIG. 7 shows a far-field image when a current is injected in the forward direction into such a phase-locked array device to cause l/− laser oscillation. FIG. 7 Ga) shows a far-field image in a direction parallel to the joint surface, and FIG. 7B shows a far-field image in a direction perpendicular to the joint surface. When the guided light of each waveguide is in the same phase, the far-field image becomes a single peak in the direction parallel to the junction surface, and its half-width is 3°, and the spread of the emitted light is small 0. : On the other hand, in the direction perpendicular to the joint surface, it is a broad single peak, and the half-width value is 30°. That is, the far-field image of the emitted light becomes an elongated ellipse with an ellipticity of 1:10.

(Problems to be Solved by the Invention) As described above, in conventional semiconductor laser array devices, especially phase-locked array devices, the emitted light has a small spread in the direction parallel to the laser bonding surface, but As a result, the far-field image of the emitted light becomes an elongated ellipse. Even when such emitted light is focused with a lens, the spot will be shaped like an ellipse, similar to the far-field image. Therefore, it is not possible to obtain a minute spot. Therefore, the conventional phase-locked array alone is not suitable as a light source for optical recording systems such as optical disks, and a special optical system must be installed near the output end face to collimate the light in the direction perpendicular to the laser bonding surface. Must be.

In addition, when using a semiconductor laser array as a light source for excitation of a YAG laser, in order to efficiently excite the fundamental mode of the YAG laser, the emitted light of the semiconductor laser array must be focused into a circular spot on the end face of a YAG rod. It is required to do so. Therefore, in this case as well, an optical system is required to correct the emitted light of the semiconductor laser array into a circular shape.

In this way, in conventional semiconductor laser array devices, the far-field pattern is not circular, so in order to use it in a system that requires circular light, a special optical system must be installed separately, and the system configuration The problem is that it becomes complicated.

The present invention is intended to solve these problems, and it is an object of the present invention to provide a semiconductor laser array device in which the far-field image of emitted light is circular with no spread.

(Means for Solving the Problems) A semiconductor laser array device of the present invention is a semiconductor laser array device having a plurality of optically coupled active waveguides and a laser beam emitting end face perpendicular to the waveguides, A reflective surface is provided opposite to the output end face, and a grating is formed on the reflective surface, thereby achieving the above object.

Laser light emitted from the emission end face of the semiconductor laser array device of the present invention is reflected by the reflective surface. At this time, the spread of light in the direction perpendicular to the laser bonding surface is suppressed by the grating. As a result, the laser beam reflected from the reflective surface is collimated, and its far-field image becomes a circular shape with no spread.

In an embodiment of the present invention, the reflective surface is a flat surface, and the angle formed with the output end surface is larger than 0° and smaller than 90°,
The line of intersection between the reflective surface and the output end face is parallel to the line of intersection between the junction face and the output end face of the semiconductor laser.

In another embodiment of the present invention, the grating on the reflective surface is configured by periodic refractive index changes or periodic irregularities in a direction perpendicular to the line of intersection between the output end surface and the reflective surface.

In yet another embodiment of the present invention, the grating on the reflective surface is provided with periodic refractive index changes or periodic irregularities also in a direction parallel to the line of intersection between the output end surface and the reflective surface.

(Example) Examples of the present invention will be described below.

FIG. 1 shows the main parts of the first embodiment of the present invention. The semiconductor laser array device of this embodiment is a laser oscillation device having the same configuration as the above-mentioned ridge waveguide type laser array device shown as a conventional example. It has part A.

In this embodiment, a laser beam emitting end face 10 is formed in the laser oscillation section A and is perpendicular to the ridge waveguide.In this embodiment, a reflecting surface 11 is formed obliquely facing the emitting end face 10. This reflective surface 11 has the following positional relationship with respect to the output end surface 10. That is, the angle formed by the reflective surface 11 and the output end surface 10 is α, and the intersection line of these surfaces is the angle formed by the output end surface 1.
0 and the laser bonding surface. The grating 30 is formed on the zero reflection surface 11, although the angle α may be 0° and α<90°, but preferably 30° and α<60°.

Next, a method for manufacturing such a semiconductor laser array device will be explained with reference to FIG. FIGS. 2(a) to 2(d) schematically show cross sections taken along line XX in FIG. 1 in each manufacturing process.

Similar to the conventional example described above, on the n-GaAs substrate 1,
n-A1. Ga, -xAs cladding layer 2, p-AI, G
An a, -, As active layer 3, a p-AI, Ga, -tAs cladding layer 4, and a p-GaAs cap layer 5 are sequentially laminated. After that, the ridge 6 and the insulation M7 are formed as in the conventional example. The entire surface of the cap layer 5 other than the portion corresponding to the output end face 10 is covered with a photoresist 20, and the output end face 10 is formed by reactive ion beam etching (second
Figure (, 1L)).

Next, the output end face 10 is also protected with a photoresist 21, and a predetermined portion 20a of the photoresist 20 is removed. This substrate is tilted by a predetermined angle α, and the reactive ion beam 2
2 (FIG. 2(b)). This etching forms an inclined surface 23 that faces the output end surface 10 and is inclined at an angle α with respect to the output end surface 10.

After etching, an A1 reflective film 24 is vacuum deposited on the inclined surface 23, and the photoresist 20.22 is removed (second step).
Figure (C)), electron beam resist 2 is placed on this reflection M24.
5, and a grating pattern 26 is formed by electron beam lithography (FIG. 2(d)).

Thereafter, an AI reflective layer is vacuum deposited and the resist 25 is removed, thereby forming a reflective surface 11 having an AIJI reflective grating 30, as shown in FIG.

This grating 30 has an output end surface 10 and a reflection surface 11.
It is composed of periodic irregularities of A11l (in the direction perpendicular to the intersection line with An n-side electrode 8 is formed on each ridge 6, and an n-side electrode 9 is formed on the substrate 1 side.

The operation of the apparatus of this embodiment will be explained.

FIG. 3 schematically shows a cross section of the main part of this embodiment along the line x-xi in FIG. When a current is injected into the laser oscillation section A in the forward direction to cause laser oscillation, the emission end face 10
Laser light 45 is emitted toward the reflective surface 11 from the reflection surface 11 .

At this time, since the emission aperture is narrow, approximately 2 μm, the laser beam
5 spreads with a spread angle (intensity half-width value) of about 30°. This diverging laser beam 45 is reflected by the reflecting surface 11, but is converted into parallel laser beam 50 by the grating 30 provided on the reflecting surface 11.

The period of the grating 30 is set so as to phase shift the wavefront of the diverging laser beam 45 to the wavefront of the collimated laser beam 50 (see "Optical Integrated Circuits" by Nishihara et al.).

The far-field image of this embodiment is shown in FIG. (&))of,
In the direction perpendicular to the laser bonding surface, the half-width is 5° (Fig. 6).
b)).

A perspective view of a main part of a second embodiment of the present invention is shown in FIG. The difference is that a groove 70 perpendicular to the grating 65 is formed in the middle of the surface. Due to the presence of this groove 7o, the reflective surface 6
0, periodic unevenness is formed in a direction parallel to the intersection line La between the emission end face 10 and the reflection surface 6°. however,
The groove 70 linearly opposes the middle run of the three ridges 6, and the convex portion of the reflective surface 6o (other than the groove 70) linearly opposes the ridges at both ends.

This unevenness serves to correct the 180° phase difference on the reflecting surface 6o when the laser oscillation unit oscillates in a 180° phase mode in which the phase of the laser light propagating through each ridge waveguide is alternately different by 180”. Therefore, a single-peak far-field image is obtained from the reflecting surface 60 in a direction parallel to the laser bonding surface.As a result, a far-field image similar to that of the first embodiment is obtained.

Note that the present invention is not limited to the refinement of each of the embodiments described above, and can be applied to, for example, the following cases: (1) Waveguides other than the ridge waveguide type shown in the embodiments (2) Any semiconductor laser array device having a branch-coupled waveguide structure other than the parallel waveguide shown in the example; (3) Any semiconductor laser array device other than the GaAs-AlGaAs system shown in the example. InP-1n
Semiconductor laser array device using other semiconductor materials such as GaAsP system, (4) In the example, the grating is formed by unevenness of A1, but it is also possible to use a semiconductor with a grating made of unevenness or a change in refractive index made of a material other than Al. (5) A semiconductor laser array device including a grating formed by a direct writing method using a focused ion beam method, although the grating in the embodiment is formed by an electron beam writing method.

(Effects of the Invention) As described above, in the semiconductor laser array device of the present invention, since the grating for suppressing the spread of the emitted light is formed on the reflective surface provided opposite to the emitting end face of the laser oscillation section, Output light having a circular, collimated, far-field image with no spread can be obtained from the reflective surface. Therefore, even when the semiconductor laser array device of the present invention is used as a light source for an optical disk system, a YAG laser, etc. that requires laser light in the form of a circular spot, a special optical system for collimating the emitted light is required. does not require.

, ・I - Cloudy day Figure 1 is a perspective view of the main part of the first embodiment of the present invention, Figure 2 (
a) to (d) are diagrams for explaining the manufacturing process of the embodiment, FIG. 3 is a sectional view taken along the line x-X in FIG. 1, and FIG. 4 is a perspective view of the main part of the second embodiment. , FIG. 5 is a perspective view of the main part of the conventional example, FIG. 6 (a> and (b) is a diagram showing a far-field image of the first embodiment, and FIG. 7 (a) and (b) is the conventional example. It is a figure showing a far-field image of.

3... Active layer, 6... Ridge, 10... Emitting end surface, 11.60... Reflecting surface, 30.65... Grating, 45... Outgoing light, 50... Reflected light .

that's all

Claims (1)

[Claims] 1. A semiconductor laser array device having a plurality of optically coupled active waveguides and a laser beam emitting end face perpendicular to the waveguides, wherein a reflecting surface is provided opposite to the emitting end face, and the reflecting surface A semiconductor laser array device with a grating formed on its surface.