JPS62268183A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To obtain excellent luminous characteristics by mutually deflecting and coupling beams in each light-emitting region and forming these beams so that frequency and phase substantially coincide with each other. CONSTITUTION:Substrate N-GaAs 101, clad-layer N-Al0.35Ga0.65As 102 and active-layer non-doped Al0.1Ga0.9As 103 are formed in succession, and P-Al0.35 Ga0.65As 104 and contact-layer P-GaAs 105 are shaped. A current constriction layer and electrodes are formed to semiconductor laser structure shaped in this manner. Current injection regions 109 are formed, and Au-Zn/Au 107 is shaped on a P-type and Au-Ge-Ne/Au 108 on an N type in the electrodes, thus forming a laser. When currents are injected to the laser, luminescent points 110 are formed onto the corresponding active layers 103 by currents injected from the sections 109. When current-injection region space 112 is brought to 2mum-25mum at that time, beams by the spreading of beams emitted from the luminescent points are mutually deflected and coupled, thus conforming phase.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a semiconductor laser device in which a plurality of semiconductor lasers are monolithically formed.

[Prior Art J] Conventionally, when designing an optical scanning device using a plurality of semiconductor lasers or light emitting diodes (LEDs), as disclosed in Japanese Patent Application Laid-Open No. 59-126, light emitting is performed as shown in FIG. The direction of light emitted from the body is one point P.

The light sources were designed such that the light sources intersected at the same angle, and the scanning spot (not shown) could be scanned with a plurality of scanning spots while maintaining a good image formation state.

FIG. 3 shows a typical conventional example, and is a diagram of the optical system between the light source and the deflector, viewed from a direction perpendicular to the deflection scanning plane. 31a and 31b are semiconductor lasers, and each laser is arranged on the mount 32 so that its light beam generating surface is parallel to the end surface of the mount 32. Mount 32 provided with semiconductor lasers 31a and 31b
The end faces 32a, 32b of each laser 31a, 31b
A point P where the central rays ha and hb of the divergent luminous flux from are the same. It is set as if it had passed through.

In other words, if normal lines are drawn to the end faces 32a and 32b at the positions where the semiconductor lasers (31a, 31b) are provided, each normal line is P. The end face 32a
and 32b are set. Furthermore, when viewed from a direction parallel to the deflection scanning plane, each semiconductor laser C) center ray h
a, hb P. The position of the semiconductor laser provided on the mount 32 is set so that the position passing through the point is slightly displaced in a direction perpendicular to the deflection scanning plane. Above P.

The point P in the predetermined vicinity of the deflection reflection surface 33 of the deflector is
An optically conjugate relationship is maintained by the imaging lens 34.

In this way, in order to arrange multiple semiconductor light emitting devices (for example, semiconductor lasers) so that their respective light emission directions are different, it is necessary to align the mounts as shown in the example above and create a hybrid. needed to be configured. For convenience, the term "array laser" will be used below to refer to a plurality of semiconductor light emitting elements, but in principle it also applies to light emitters such as LED arrays.

Furthermore, when using an array laser formed as a monolink, it is necessary to install some kind of optical system in front of the array laser. In an example disclosed in Japanese Patent Laid-Open No. 58-211735, a prism is placed in front of an array laser. This is shown in FIG.

FIG. 4 shows a cross section of a prism when a semiconductor array laser has five light emitting parts. 41 is five light emitting parts (41a, 41b, 41c, 41d, 41
42 is a prism. The central ray ha of the luminous flux from the light emitting part 41a is refracted by the inclined surface 42a, and the central ray ha of the luminous flux is refracted as if by P. It is bent as if it had passed through. Similarly, the central ray h from 41b
b is caused by the inclined surface 42b, the central ray hd from 41d is caused by the inclined surface 42d, and the central ray he from 41e is caused by the inclined surface 42e, as if P.

It is bent as if it had passed through. Note that the central ray hc from 41c passes through the plane 42c perpendicularly, and P is on the extension line of this central ray hc. exists.

In this way, an inclined plane with a defined inclination angle is provided corresponding to each light emitting section, and the center ray of each luminous flux after exiting the prism 42 is as if P. Its direction is controlled as if it were emitted from a source. This P. As described above, is maintained conjugate with a desired position P (not shown) near the deflection/reflection surface through the optical system. Problems in this case include the precision and method of microfabrication of the prism 42, the alignment and bonding method between the prism 42 and the array laser 41, and the smaller the pitch of the array laser, the more difficult it becomes. In fact, it is almost impossible if the thickness is less than 100 μm.

On the other hand, FIG. 5 shows an attempt to have a similar effect with an optical system, that is, a relay optical system 53, with array lasers 51a, 5
This is an example in which a relay optical system 53 is interposed between a collimating lens 52 and a cylindrical lens 55, which collimate the light emitted from 1b and form an image, and an image is formed on a polygon surface 54. An image is formed on a scanning plane (not shown).

The problem in this case is the optical path length, and the relay system itself is approximately 2
It becomes 0 cm longer.

On the other hand, in order to solve the above-mentioned problems, the present applicant has published Japanese Patent Application No. 59-240418, Japanese Patent Application No. 60-424, etc., in which a plurality of semiconductor lasers are formed in a monolith.
Furthermore, a semiconductor device in which each semiconductor laser has a different emission direction has already been proposed.

[Summary of the invention]

An object of the present invention is to provide a semiconductor laser device that can be easily manufactured and that can be combined with lenses etc. to construct an optical system with a short optical path length. This will further improve the

A semiconductor laser device according to the present invention is a semiconductor device in which a plurality of semiconductor lasers are monolithically formed.
A feature of the above-described semiconductor laser is that the respective directions of light emission are different when the light is emitted from the respective resonant surfaces of the semiconductor laser.

Note that the expression "the directions of light emitted from each laser are different" used in the following description does not mean that there are no sets of lasers that emit light in the same direction, but in a broad sense, there is one set of lasers that emit light in different directions. This means that there are more than one set.

The problem with integrating a large number of semiconductor lasers at high density is that the emission efficiency decreases due to heat generation due to carrier injection during oscillation and temperature rise, and it is no longer possible to obtain a constant optical output with a constant injection current. . This is 1 when using a semiconductor laser as a light source for an optical recording device.
This causes recording errors and deterioration of recording quality.

The specific solution presented in the present invention is to form each semiconductor laser so that each semiconductor laser emits light with substantially the same frequency and phase in order to prevent the above-mentioned reduction in luminous efficiency. The device is configured to have a plurality of light emitting regions, and improves light emitting characteristics. That is, by adopting the above structure as described in the following embodiments, (1) the injection current required for light emission is reduced, the amount of heat generated to obtain the same level of light output is reduced, and the operating temperature is lowered.

(2) Good temperature characteristics, with little fluctuation in light output even during high-temperature operation.

(3) There is little variation in performance between adjacent elements, and homogeneous output can be obtained from a plurality of output ends.

(4) The light emitting area could be increased and high output could be obtained.

Due to the above-mentioned combined effects, good light emission characteristics can be obtained regardless of the light emission history in the obliquely emitting array laser that is highly integrated as in the present invention.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. In the figure, 11 to 15 indicate individual semiconductor lasers, and 11 to 15a correspond to current injection regions, that is, light emission regions in each of the semiconductor lasers 11 to 15. Then, the angles formed by extension lines (hereinafter referred to as resonance directions) 11b to 15b of the injection regions 11a to 15a and the normal line 18 to the resonance surfaces 16 and 17 are φa, φb2, φC2φd, and φe, respectively. is formed.

Note that the resonance planes 16 and 17 are usually parallel because the cleavage planes of a crystal (e.g., GaAs) used as the substrate are used, but in cases such as dry etching where the degree of parallelism may be slightly different, Consider the resonant surface 16 on the laser emission front side as a reference.

When the light resonated at the resonant surfaces 16 and 17 is emitted from the resonant surface 16 as a laser beam, it is bent according to Snell's law. In the figure, llc to 15c indicate the light emission direction.

Here, if the angle between an arbitrary light emission direction and the normal line 18, that is, the emission angle, is θ, then n / n O= S l
The relationship nθ/sinφ holds true. For example, considering the case where the laser beam is emitted from a GaAs crystal, n (the refractive index of the crystal) is approximately 3.5 and no (the refractive index of the air) is approximately 1, so if φ is advanced by 1 degree, the laser beam Approximately 3゜5 for law vA18
It emits at a rate of 1 yen.

In the embodiment shown in FIG. 1, φa, φb, φC9φd, φ
e is +1.0 degree, +0.6 degree, and 0.0 degree, respectively.

By setting -0.5 degrees and -1.0 degrees, the output angles θa, θb, θC1θd, and θe are +3 and 5 degrees, respectively.
Degree, +! , 75 degrees, 0.0 degrees, -1,75 degrees,
We were able to create an array laser with an angle of -3.5 degrees.

FIG. 6 is a sectional view taken along line A-A' in FIG. 1.

The manufacturing process will be described in detail below using this diagram.

FIG. 6 shows an uninvented embodiment i1. In FIG. 6(a), 101 is a substrate n-GaAs. 102 is a cladding layer n Af o, 35 G
a o, 65 As 1.5 μm, 103 is the active layer non-doped AlO, I Ga O, g As 0
．． It is 1 μm. Furthermore, 104 is p-AA Q, 3
5 Ga 0.6 s As 1-"u".

Furthermore, 105 is a p-GaAs contact layer.
It is 0.5 μm. Current confinement and electrode formation must be performed on the semiconductor laser structure thus formed. 106 is an insulating layer 510 that performs current confinement.
The thickness of two films is 0.3 μm. This film is partially separated into stripes by ordinary photolithography to form a current injection region 109. After this, an electrode is formed on the p
For the type, u-Zn/Au.

In the case of 108 n-type, A u −G e −N i /
A laser can be formed by forming Au.

When a current is injected into this laser, the current injected from the portion 109 forms 110 light emitting points on the active layer 103 corresponding to the portion 109. At this time, when the interval between the current injection regions 112 is set to 2 It m to 25 μm, the emitted light spreads and the mutual light is deflected and combined, thereby matching the phases. This results in (1) good coherence in which the degree of beam divergence in the far-field optical fringe pattern is small over a wide range of pumping currents, and (2) a narrow spot spacing that provides good coherence when viewing the far-field optical pattern. Since it behaves as if it were a single spot and has a large light emitting area, high output can be achieved.

It has the following characteristics. This laser array with narrow current injection intervals is used as one laser section 113 of the oblique emitting laser described above, as shown in FIG. 6(c).

Note that although an n-GaAs substrate is used in the present invention, an n-GaAs substrate may also be used. However, the polarity of each semiconductor layer at that time must be opposite to that of the present invention. In other words, n-type must be changed to p-type, and p-type must be changed to n-type. However, the active layer may be free of impurities.

In this example, current is injected into the laser using electrode stripes, but various methods may be used for the injection, such as a method using litun, a method of forming a current confinement layer in the grown film, etc. What is important here is that the spacing between adjacent lasers is small, resulting in light coupling.

In the semiconductor device according to the present invention, array lasers with different light emission directions are created using cleavage planes, but the present invention is not limited to array lasers using cleavage planes. Depending on mounting considerations, it is also possible to employ, for example, a resonant surface formed by a wet process or a dry process on one side or both sides. Examples are shown in Figures 2-1 and 2-2.

In each figure, 213a to 213e, 223a to
223c is an injection region, each having an independent injection electrode. 214a to 214e, 2], 5a to 2
]5e (b.

(c, d not shown) are the resonator surfaces formed by etching. Also, in Figure 2-2, 224a
.

2211, b, 224 c, 225 a
, 225 b and 225 c are the resonator surfaces formed by etching.

It should be noted that the first semiconductor layer which is the active layer shown in the claims and the second semiconductor layer sandwiching this are the active layers. In the third semiconductor layer structure, the second. The third region includes a superlattice structure that is not an active layer and a semiconductor layer whose composition is continuously changed, and the generation layer is a region where carrier recombination mainly occurs and a region of carrier recombination. Number 1000 formed adjacent to each other
It also contains a thin layer of less than Å. For example, a single child well (
A thin layer of 0.1 μm or less that causes light confinement, such as a barrier layer of several to several thousand layers formed on both sides of a multiple single well, and a normal layer of about 0.1 μm. .

[Effect of the Invention 1] As explained above, the present invention has made it possible to extract homogeneous output with high luminous efficiency and high reproducibility from different emission directions in a conventional semiconductor laser device. Furthermore, since the light emitting direction from each laser is different, laser beams from multiple points can be imaged well on the medium using a scanning optical system, making it suitable as a light source for optical devices such as laser beam printers. Extremely advantageous.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an embodiment of a semiconductor device according to the present invention, FIGS. 2-1 and 2-2 are plan views showing modified examples of the present invention, and FIG. 3 is a plan view showing a semiconductor device according to an embodiment of the present invention. Figure 4 shows a conventional example in which an array laser with a constant output direction and a prism are combined to have different output directions, and Figure 5 shows an attempt to correct an array laser with a constant output direction using an optical system. FIGS. 6(a), 6(b), and 6(c) are schematic cross-sectional views each showing an example of the configuration of a semiconductor laser. 11-15... Semiconductor laser, 16, 17... Resonance surface.

Claims (1)

[Claims] (1) In a semiconductor laser device in which a plurality of semiconductor lasers are monolithically formed, the light emitting region of the active layer of each semiconductor laser is restricted in the form of a stripe, and the direction of the stripe is at an angle with the resonant plane. The semiconductor laser has different wavelengths and is configured to emit a plurality of lights in different directions, and the lights are mutually deflected and combined in each of the light emitting regions, and these lights are substantially different in frequency and phase. A semiconductor laser device characterized in that the semiconductor laser device is formed to match.