JPH04302190A - Multi-beam semiconductor laser - Google Patents

Abstract

PURPOSE:To obtain a multi-beam semiconductor laser in which laser rays are surely and separately detected, controlled, and driven. CONSTITUTION:Laser waveguides 4 are disposed in parallel, secondary gratings 5 are formed at different positions in the resonator lengthwise direction of the waveguide 4, and photodetectors 9 are disposed in parallel in a direction which intersects the resonator lengthwise direction of the waveguide 4 traversing the gratings 5.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-beam semiconductor laser, particularly an automatic output control type multi-beam semiconductor laser.

0002

[Prior Art] Semiconductor lasers generally use so-called automatic output control (APC), which detects the optical output with a light receiving element and maintains the optical output constant in order to suppress fluctuations in output caused by temperature changes, characteristic deterioration, etc. :Auto Po
control) drive. That is, in a typical semiconductor laser, as shown in the schematic enlarged side view of FIG. A photodetector element 21 such as a photodiode that receives the backward light LB from the element 12 is mounted, and the detection output from the photodetector element 21 is used to detect the AP.
It is designed to perform C drive. LF is the forward light of the semiconductor laser element 12.

When the configuration for performing APC driving as described above is directly applied to a multi-beam semiconductor laser, that is, a semiconductor laser array, the multi-beam semiconductor laser 10 as shown in the schematic enlarged top view of FIG. The photodetector element 21 receives the sum of the plurality of lights LB from behind, making it difficult to monitor each semiconductor laser independently.

Furthermore, as shown in the schematic enlarged top view of FIG. Since the light emitted from each semiconductor laser element has a certain degree of spread, the distance d between these photodetecting elements 21 and the light emitting surface 1S of the multibeam semiconductor laser 10 needs to be a minute distance of about several μm. There was a problem that it was difficult to realize an independent monitor.

On the other hand, an optical semiconductor device that is designed to independently detect light of different wavelengths for one laser beam has been proposed in Japanese Patent Application Laid-Open No. 111679/1983. This optical semiconductor device has a configuration in which gratings (diffraction gratings) with different Bragg reflection conditions are formed on a common waveguide, and each wavelength is detected by a light receiving element provided at a position corresponding to each grating. .

[0006] With this configuration, it is possible to independently detect light of different wavelengths corresponding to the Bragg conditions of each grating, and since the grating is used as a demultiplexer, it has excellent wavelength selectivity. In this case, an optical semiconductor device is obtained.

However, in this case, a plurality of gratings are formed in the same waveguide, and no consideration has been given to a configuration in which a plurality of laser beams having the same wavelength are simultaneously detected individually.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to obtain a multi-beam semiconductor laser that can reliably detect the outputs of a plurality of laser beams individually.

[0009]

[Means for Solving the Problems] FIG. 1 shows a schematic enlarged top view of an example of a multi-beam semiconductor laser according to the present invention. As shown in FIG. 1, the present invention arranges a plurality of laser waveguides 4 in parallel, and forms secondary gratings 5 at different positions in the resonator length direction of the laser waveguides 4. Each grating 5 in the direction intersecting the length direction
The photodetecting elements 9 are arranged in parallel across the top.

0010

[Operation] As described above, in the multi-beam semiconductor laser of the present invention, the secondary gratings 5 are formed at different positions on the plurality of laser waveguides 4, and each of the secondary gratings 5 is With this configuration, the guided light in each laser waveguide 4 is diffracted vertically upward by each secondary grating 5, and each secondary grating 5 They can be individually detected by the photodetecting elements 9 individually provided above.

[0011] Therefore, the outputs of a plurality of laser beams emitted from the multi-beam semiconductor laser can be reliably detected individually.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of an automatic output control type multi-beam semiconductor laser according to the present invention will be explained in detail below with reference to FIGS. 1 and 2. In this case, this is an example of a hybrid configuration of the semiconductor laser element 12 and the photodetector element 9.

FIG. 2 is a schematic enlarged cross-sectional view of a main part along the cavity length direction of one semiconductor laser element in the multi-beam semiconductor laser 10 of the present invention. In FIG. 2, 1 is an n-type GaAs substrate, for example. Then, on this substrate 1, there is a cladding layer 2 made of a first conductivity type, for example, n-type Al0.3Ga0.7As, and further on this, an active layer 3 made of undoped GaAs, etc., and a layer 3 made of Al0.15Ga0.85As, etc. The waveguide layer 4S is sequentially deposited by, for example, MOCVD (metal organic chemical vapor deposition).

A plurality of secondary gratings 5 are then formed on this waveguide layer 4a. These gratings 5 are
For example, by applying a two-beam interference exposure method, photoresist coating, two-beam interference exposure using an Ar laser, development, etc.
By performing processing such as anisotropic etching using this as a mask, it is formed with a pitch that satisfies the second-order Bragg condition with respect to laser light of a predetermined wavelength.

[0015] Furthermore, these plurality of gratings 5 (5a
, 5b, 5c...) are, for example, the dashed lines x1, x2,
As shown in x3 . . . , they are formed at different positions with required intervals in the y direction on a line having a required interval along a predetermined y direction.

[0016] Further, on this secondary grating 5, a second
A cladding layer 6 of conductivity type, for example, p-type Al0.3 Ga0.7 As, is formed by MOCVD or the like, and electrodes 7 (7a, 7b, 7c...
) is deposited and formed.

This electrode 7, for example, as shown in FIG.
Extending in the y direction, a parallel strip pattern is formed on each of x1, x2, x3 by anisotropic etching such as RIE (reactive ion etching).

Further, a transparent insulating layer 8 made of SiN or the like is deposited thereon. Then, grooves 13 are formed in the region sandwiched between these electrodes 7 by anisotropic etching such as RIE to a depth that reaches the active layer 3 as a strip pattern extending parallel to each electrode 7, that is, along the y direction. Form.

In this way, each electrode 7 (7a, 7b,
7c...) By the waveguide layer 4S described below,
Each laser waveguide 4 (4a, 4b, 4c...) is formed, and each laser waveguide 4 (4a, 4b, 4c) is formed with a plurality of semiconductor laser elements 12 (12a, 12
b, 12c...) are constructed.

[0020] Then, on the semiconductor substrate on which the plurality of laser waveguides 4 are formed in this way, photodetecting elements 9 (9a, 9b, 9c...), which are formed separately, are attached using a transparent adhesive or the like. .

[0021] This photodetecting element 9 (9a, 9b, 9c...
) is formed by, for example, diffusing a p-type impurity such as B to a predetermined depth on an n-type Si substrate, and as shown in FIG.
Each grating 5 (5a, 5b, 5c...) is placed above the position where the secondary grating 5 (5a, 5b, 5c...) is formed in each laser waveguide 4 (4a, 4b, 4c...).
...), and is extended and fixed along the x direction perpendicular to the y direction.

Although not shown in the drawings, the electrodes of the photodetecting element 9 are, for example, formed by forming one electrode on the upper layer, for example, the p layer, and by removing part of the p layer and the i layer and removing part of the n layer. It is exposed to the outside and provided by forming the other electrode there.

Regarding each semiconductor laser element 12,
Although not shown, a common electrode is formed on the back surface of the base 1, for example.

In this way, a plurality of laser waveguides 4 (
4a, 4b, 4c....) are arranged in parallel, and secondary gratings 5 (
5a, 5b, 5c...) are formed, and a laser waveguide 4 (
Photodetecting elements 9 (9a, 9b, 9c...) are arranged in parallel across each grating 5 (5a, 5b, 5c...) in a direction intersecting the resonator length direction of the gratings 5 (4a, 4b, 4c...). Multi-beam semiconductor laser 1 of the present invention comprising
You can get 0.

In this case, each semiconductor laser element 12 (12
a, 12b, 12c...), the laser waveguide 4 (
4a, 4b, 4c...) are respectively diffracted upward by the secondary gratings 5 (5a, 5b, 5c...), and these secondary diffracted lights are respectively diffracted by the photodetecting elements 9 (9a, 9b, 9c...).

Therefore, it is possible to obtain a multi-beam semiconductor laser in which the output of the laser light in each laser waveguide 4 can be reliably and independently detected, and by detecting the optical output individually in this way, each semiconductor The optical output of the laser elements 12 can be individually and independently controlled and driven.

Note that the above-mentioned multi-beam semiconductor laser 1
0, a hybrid configuration was used, but after the substrate on which each pin layer was laminated was fixed on the transparent insulating layer 8, grooves were formed between the corresponding positions on each grating 5 provided in each laser waveguide 4. forming each photodetector element 9a,
Various configurations are also possible, such as a monolithic configuration by separating 9b and 9c.

Furthermore, as the constituent material of the semiconductor laser described above, an AlGaAs-based material is formed on a GaAs substrate, but other materials having a heat dissipation effect such as GaAs,
We can form various semiconductor lasers such as InP type, and
Various materials can be used, such as configuring the photodetecting section by diffusing impurities such as B on a type Si substrate.

[0029]

As described above, according to the multi-beam semiconductor laser of the present invention, the guided light in each laser waveguide 4 is
The light is diffracted by each secondary grating 5 in a direction perpendicular to the extending direction of the laser waveguide 4, and can be individually detected by a photodetecting element 9 individually provided on each secondary grating 5. Accordingly, the output of each semiconductor laser element 12 can be reliably controlled and driven independently.

[Brief explanation of drawings]

FIG. 1 is a schematic enlarged top view of an example of a multi-beam semiconductor laser according to the present invention.

FIG. 2 is a schematic enlarged cross-sectional view of a main part of an example of the multi-beam semiconductor laser of the present invention.

FIG. 3 is a schematic enlarged side view of an example of a semiconductor laser.

FIG. 4 is a schematic enlarged top view of an example of a conventional multi-beam semiconductor laser.

FIG. 5 is a schematic enlarged top view of an example of a conventional multi-beam semiconductor laser.

[Explanation of symbols]

1 Board 2 First conductivity type cladding layer 3 Active layer 4 Laser waveguide 5 Secondary grating 6 Second conductivity type cladding layer 7 Electrode 8 Transparent insulation layer 9 Photo detection element 10 Multi-beam semiconductor laser 12 Semiconductor laser element

Claims (1)

[Claims] Claim 1: A plurality of laser waveguides are arranged in parallel,
Secondary gratings are formed at different positions in the cavity length direction of the laser waveguide, and photodetecting elements are arranged in parallel across each of the gratings in a direction intersecting the cavity length direction of the laser waveguide. A multi-beam semiconductor laser characterized by: