JPH06104535A - Multibeam semiconductor laser - Google Patents

Abstract

PURPOSE:To provide a multibeam semiconductor laser in which the interval of laser beam can be shortened without causing thermal interference between resonators and to increase design freedom of a system such as optical disk unit or magnetooptic disk unit employing the multibeam semiconductor laser. CONSTITUTION:A plurality of lasers 20A, 20B, each having resonator length in the direction of crystal axis <001>, are disposed while opposing the light emitting edges on the main face, i.e., the crystal face {100}, of a semiconductor substrate. Crystal grow mirror faces 9A, 9B, each comprising a crystal face {110} making an angle of 45 deg. to the main face of the substrate, are disposed between the light emitting edges while opposing, respectively, thereto.

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 in which a plurality of semiconductor lasers are formed on a semiconductor substrate and a plurality of light beams are emitted.

[0002]

2. Description of the Related Art A multi-beam semiconductor laser is a light source for a high-speed, high-definition laser printer, or an optical disk as a two-beam laser or a four-beam laser as shown in the schematic enlarged perspective views of FIGS. 11 and 12, respectively. It is used for parallel writing and parallel reading of a magneto-optical disk and the like. At this time, as a general optical system for processing a plurality of beams, a single simple optical system similar to that used in a normal single-beam laser is used, so that the intervals between the emitted beams are wide. Since problems such as aberration of the lens occur, it is necessary to set the interval of the laser beams to a narrow interval that does not cause a problem in the optical system. Also,
A narrow beam interval is desired in consideration of the matching with the track pitch on the disk surface.

However, in the case of a semiconductor laser, especially a high-power semiconductor laser used for a magneto-optical disk, when the beam interval is narrowed, thermal interference between adjacent lasers becomes a problem (for example, "Electronics by Tsunekata et al. IEICE Technical Report OQE88-6 "). In order to avoid this thermal interference, the beam interval must be widened, and at present, the interval is widened to the limit that can be used in the optical system used, and the laser beam interval shown by L _O in FIG. ˜100 μm.

[0004]

On the other hand, the applicant of the present invention previously filed in Japanese Patent Application No. 4-127564 to extend in the <001> crystal axis direction on the main surface of the semiconductor substrate consisting of {100} crystal faces. And a reflecting mirror surface that spontaneously forms 45 ° with the main surface is formed by performing epitaxial growth by MOCVD (Chemical Vapor Deposition by Metal Organic Metals) or the like facing the resonator end surface. As a result, we have proposed a surface emitting semiconductor laser that emits light emitted from a resonator in a direction orthogonal to the substrate.

As shown in FIG. 13 which is a schematic enlarged cross-sectional view of this laser, this laser has a first cladding layer on a main surface 2 of, for example, a (100) crystal plane of a substrate 1 made of GaAs or the like. 3, the active layer 4, the second cladding layer 5 and the cap layer 6 are epitaxially grown, and then the end faces 7A and 7B constituting the resonator are etched to form a dielectric layer, for example, on the entire main surface 2 In the direction orthogonal to
Anisotropic etching such as (reactive ion etching) is performed to form the dielectric protective layer 8 only on the end faces 7A and 7B. Then, after that, when epitaxial growth is performed on the entire surface by MOCVD or the like, crystal growth mirror surfaces 9A and 9 facing the end surfaces 7A and 7B and forming a 45 ° angle with the main surface 2 are formed.
B grows spontaneously. Therefore, there is an advantage that each light beam L _O can be efficiently extracted in the direction perpendicular to the main surface 2 by utilizing this mirror surface.

The present invention provides a multi-beam semiconductor laser which can narrow the laser beam interval without causing thermal interference between the resonators by using such a structure, and an optical disk device and a magneto-optical device using the same. The purpose is to improve the degree of freedom in designing systems such as disk devices.

[0007]

A multi-beam semiconductor laser according to the present invention is a semiconductor substrate having a {100} crystal plane as a main surface, as shown in schematic enlarged perspective views of respective examples of the multi-beam semiconductor laser. , Which have a cavity length in the <001> crystal axis direction, are arranged so that their respective light emitting end faces face each other, and the light emitting end faces of the substrate are placed between these light emitting end faces. The crystal growth mirror surfaces 9A, 9B, ... Made of {110} crystal surfaces forming an angle of 45 ° with the main surface are provided so as to face the respective light emitting end surfaces.

Further, according to the present invention, in the above-mentioned multi-beam semiconductor laser, two light beams are formed as shown in FIG.

Furthermore, the present invention is a multi-beam semiconductor laser as described above, wherein a light beam is divided into four beams as shown in FIG.
Configure as a book.

Further, the multi-beam semiconductor laser of the present invention comprises:
As shown in FIG. 3, a schematic enlarged plan view of an example thereof is shown in FIG.
<0} on the main surface of the semiconductor substrate having the crystal plane as the main surface, <0
01> A plurality of lasers that emit a light beam in at least a first direction along the crystal axis direction are formed, and the lasers face each other between the light emitting end faces of the lasers and have a direction opposite to the first direction. A laser that emits a light beam in
A crystal growth mirror surface composed of a {110} crystal surface forming an angle of 45 ° with the main surface of the substrate is provided so as to face the light emitting end surface of each of these lasers.

Further, according to the present invention, in each of the above-mentioned multi-beam semiconductor lasers, the distance between each light emitting end face and the crystal growth mirror face is modulated and provided for each laser.

[0012]

As described above, in the present invention, the semiconductor substrate is provided with the resonator along the <001> crystal axis direction on the main surface of the {100} crystal plane, and along the <001> crystal axis direction. A plurality of lasers for emitting a light beam in a predetermined direction are provided. As described above, when epitaxial growth is performed at a position facing each light emitting end face of these lasers, a crystal growth mirror forming 45 ° with respect to the main surface of the substrate. Since the surface is spontaneously grown and formed, it is possible to use this mirror surface to emit a plurality of emitted light L _O from each laser in a direction perpendicular to the main surface of the substrate. it can.

[0013] Thus, the distance between the mirror surface according to the present invention by small, the spacing of the outgoing light L _O of the laser without causing heat interference problems remarkably compared with the conventional multi-beam semiconductor laser Therefore, the multi-beam laser can be easily configured with an easy-to-use beam interval according to the optical system and the track width.

Further, as described above, since the surface naturally obtained by crystal growth is used as the 45 ° reflecting mirror,
Compared with a conventional reflecting mirror surface formed by oblique etching or the like, it has excellent flatness and angular accuracy, and an ideal reflected beam with no aberration can be obtained. The manufacturing can be remarkably simplified as compared with the semiconductor laser.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings. In each of the examples, a GaAs semiconductor substrate is used, and a clad layer of the first conductivity type is epitaxially grown thereon,
The case where a multi-beam semiconductor laser is formed by sequentially forming an active layer and a clad layer of the second conductivity type to form each laser and further forming a crystal growth mirror surface is shown.

First, an example of a multi-beam semiconductor laser having two light beams will be described with reference to FIG. First G
For example, (10
0) on the major surface composed of crystal planes, the <001> crystal axis direction,
In this case, 2 having a resonator along the [001] crystal axis direction
Two lasers 20A and 20B are arranged so that the light emitting end faces thereof face each other, and in this case of (110) crystal planes forming 45 ° with respect to the main surface of the base body between the respective light emitting end faces (10
1) A crystal growth mirror surface 9A composed of crystal planes and (10-
1) A crystal growth mirror surface 9B made of a crystal surface is provided so as to face each light emitting end surface.

An example of a method of manufacturing such a semiconductor laser will be described with reference to the manufacturing process diagrams of FIGS. As described above, in this case, as shown in FIG. 5A, on the main surface 2 made of the (100) crystal plane of the semiconductor substrate 1 made of n-type GaAs, the first surface made entirely of n-type AlGaAs or the like, as shown in FIG. 5A.
Clad layer 3, an active layer 4 made of intrinsic GaAs, and a second clad layer 5 made of p-type AlGaAs,
Further, the cap layer 6 made of p-type GaAs or the like is sequentially MOCed.
A double hetero structure that forms a semiconductor laser is formed by epitaxial growth by the VD method or the like. In this case, a current confinement layer or an optical waveguide layer can be formed if necessary.

Then, as shown in FIG. 5B, by applying photolithography or the like, an end face forming an angle of 90 ° with the main surface 2 by anisotropic etching such as RIE, in this case, (00-1) crystal face End faces 7A and (00
1) An end face 7B made of a crystal face is formed. That is, in this case, as shown by the arrow in FIG. 5B, the resonator extends in the direction along the [001] crystal axis direction.

After this, the entire surface is covered with SiO ₂ , SiN _x.
After depositing a dielectric layer made of Al, etc., anisotropic etching such as RIE is performed on the entire surface in a direction orthogonal to the main surface 2 so as to cover the cap layer 6 and the main surface 2 between the end surfaces 7A and 7B. Removing the dielectric layer of end faces 7A and 7B as shown in FIG. 5C.
A dielectric protection layer 8 is formed so as to cover the. Thereby, the end face reflectance is adjusted as needed. Then, the cap layer 6 is slightly etched in the thickness direction so that the top of the dielectric protection layer 8 is slightly projected from the upper surface of the cap layer 6.

Next, as shown in FIG. 6A, a MOCV semiconductor layer made of the same material as the cap layer such as p-type GaAs is entirely formed.
When re-grown by the D method or the like, crystal growth does not occur on the dielectric protection layer 8 and the main surface 2 between the end faces 7A and 7B of each resonator is formed.
On the top and the cap layer 6, a crystal growth surface forming 45 ° with respect to the principal surface 2 spontaneously grows so as to face the end face of each resonator, that is, face the end face 7A (101). Opposite the mirror surface 9A composed of crystal planes and the end surface 7B (10-
1) A mirror surface 9B made of a crystal surface is formed.

After that, as shown in FIG. 6B, a high reflection layer 10 made of Au, a dielectric multilayer film or the like is deposited so as to cover the mirror surfaces 9A and 9B, and the cap layer 6 is further formed.
Electrodes 11 and 12 are formed on the upper regrowth layer 9 and the back surface of the substrate 1 by sputtering or the like so that light emitted from the lasers 20A and 20B is reflected on the mirror surfaces 9A.
And 9B is emitted in a direction perpendicular to the major surface 2, it is possible to beam spacing obtain a multi-beam semiconductor laser for emitting a light beam L _O of two that is narrowed.

In such a configuration, each laser 20
By properly selecting the distance between the end faces of A and 20B, the distance between the crystal growth mirror surfaces 9A and 9B can be adjusted, and the laser beam distance can be narrowed without causing thermal interference between the lasers.

Further, in the above-mentioned embodiment, the case of a multi-beam semiconductor laser having two light beams is used. For example, as shown in FIG. 2, lasers facing each other extending in the [001] crystal axis direction. 20A and 20B, and two lasers 20C and 20D extending in the [010] crystal axis direction orthogonal to these are formed, and, for example, a {110} crystal plane is formed so as to face each emission end surface of these lasers 20C and 20D. Crystal growth mirror surface 9 composed of (110) crystal surface
C, crystal growth mirror surface 9D consisting of (1-10) crystal surface
Can be spontaneously formed by crystal re-growth in the same manner as in the above example, and the light beams from the respective lasers are arranged and emitted in a square shape in a direction perpendicular to the main surface of the substrate. Become.

In this case, the normal four-beam lasers are arranged in a row horizontally, whereas the beams are arranged in a square shape. For example, when the beams are used as a processing light source for a track of an optical disk, as shown in FIG. In addition, the parallel processing can be performed by arranging the spots 32 of the respective beams so that the different tracks 31 are irradiated.

Further, for example, as shown in FIG. 8, two spots 32 are irradiated on the same track 31, one laser beam is used for writing for one track, and immediately after that by another laser beam. It is possible to increase the degree of freedom in system design, such as a configuration in which reading is performed.

Next, another example of the present invention will be described in detail with reference to FIG. 3, parts corresponding to those in FIGS. 1 and 2 are designated by the same reference numerals. In this case, {100}
On the main surface of the semiconductor substrate having the crystal plane as the main surface, <001>
At least a first direction along the crystal axis direction, in this case [0
01] A plurality of lasers 2 for emitting a light beam in the crystal axis direction
0A is formed, and the light emitting end faces of the laser are opposed to each other, and the [0 0 1] direction opposite to the first direction is set.
A laser 20B that emits a light beam in the direction of the crystal axis is configured to face the light emitting end faces of each of the lasers 20A and 20B and form 45 ° with respect to the main surface of the substrate {110}.
It is configured by providing crystal growth mirror surfaces 9A and 9B composed of crystal planes.

That is, in this case, paying attention to the light emitting portions on one side of the semiconductor lasers shown in FIGS. 1 and 2, a plurality of these are arranged in parallel, and the lasers are similarly arranged in parallel at positions corresponding to each laser. Then, the pseudo light emitting points emitted from one end face of each laser and reflected by the mirror surface are arranged in a straight line, and by arranging the resonator bodies alternately in a zigzag manner, A one-dimensional semiconductor laser array can be obtained. At this time, the other end face of each laser is provided with a high-reflection coating layer so that light is not emitted, or a light beam is prevented from being emitted in a direction perpendicular to the substrate by cleavage end faces or etching.

As a method of manufacturing such a semiconductor laser, for example, a semiconductor substrate made of n-type GaAs or the like {10 is used.
0} crystal plane on the main surface, a first clad layer made of n-type AlGaAs or the like, an active layer made of GaAs or the like, p
After a second clad layer made of AlGaAs or the like, a cap layer, etc. are sequentially epitaxially grown, as shown in the manufacturing process diagram of FIG. 9, the respective resonators are alternately arranged in a zigzag pattern as described above. The end faces and side faces of the resonator are vertically etched by RIE or the like, and the hatched region in FIG. 9 is removed by etching.

After that, a dielectric layer is entirely deposited,
The dielectric protective layer 8 is formed by patterning so as to cover the end faces and the side faces of the resonators that are alternately opposed to each other. Figure 1
In FIG. 5, the portion where the protective layer 8 is provided is shown by hatching.
Then, after that, when epitaxial growth is performed by MOCVD or the like, [00
1] A crystal growth mirror surface 9 composed of a (10-1) crystal surface for each end surface of a laser 20A that emits light in the crystal axis direction.
A, laser 20 for emitting light in the [00-1] crystal axis direction
A crystal growth mirror surface 9B composed of the (101) crystal plane is spontaneously formed on each end face of B, and is shown in FIG.
The light beams can be respectively extracted in the direction orthogonal to.

In this case, by appropriately selecting the distance between the end faces of the lasers 20A and 20B in the cavity length direction and the thickness of the dielectric protective layer 8 on each emitting end face, the light is reflected by each mirror surface. It is possible to form a one-dimensional array laser by arranging the positions, that is, the light emitting points, on a straight line.
For example, when the lateral distance between the lasers, that is, the arrangement distance in the direction orthogonal to the cavity length direction is 50 μm, the distance between the laser lights can be 25 μm, which is ½ of the distance. Compared with a laser, it has an advantage that the distance between light beams can be narrowed to about 1/2 without causing thermal interference.

Further, various configurations can be adopted such as changing the number of lasers according to other uses, or arranging light emitting points in a zigzag pattern.

In each of the above-mentioned multi-beam semiconductor lasers, the distance between each light emitting end face and the crystal growth mirror face may be modulated and provided for each laser. Figure 4
An example of this laser will be described in detail with reference to. 4, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and duplicate description will be omitted. In this case, in the laser having two light beams described in FIG. 1, the distance between the light emitting end surface and the mirror surfaces 9A and 9B is offset at the base side edge portion of the dielectric protection layer 8 and, for example, one of Each of the lasers 2 is formed by patterning the dielectric protection layer 8 as a pattern in which a protrusion having a length L is provided so as to face the mirror surface 9B.
The focal positions of the output light L _O from 0A and 20B are made to have different depths as indicated by points P ₁ and P ₂ , respectively, and in this case, the focal length on the side of the laser 20B provided with the protruding portion is larger. Configured to be large.

The two-beam semiconductor laser device whose focal length is thus modulated can be used, for example, in a servo control system utilizing the difference in the focal lengths of the two beams.
In FIG. 10, each circle represents a beam spot diameter, and
In the left column and the right column in FIG.
It corresponds to the beam spots from A and 20B. Figure 10A
In the examples of B and B, only the laser 20A detects the light amount of the detection element 33, and the laser 20B has a light amount of zero. Figure 10
In C, the light quantity of the laser 20A increases and the laser 20A
Although the light amount of B is also detected, the light amount of the laser 20A is larger. Similarly, in FIGS. 10D and 10E, the light amount of the laser 20A is larger, but in the example of FIG. 10F, the light amounts are almost equal. On the contrary, in FIGS. 10G to 10E, the light amount of the laser 20B becomes larger and the light amount difference gradually becomes larger, and in FIGS.
The light quantity of A is no longer detected.

Therefore, in this case, by controlling the state of FIG. 10F, that is, by controlling the difference in the amount of light to be 0, it is possible to perform the focus servo control while holding the controlled object at a constant distance.

In each of the above examples, AlGaAs
Although the case of forming a system laser is shown, the present invention can be applied to other compound semiconductor lasers such as AlGaInP system and InGaAsP system. Needless to say, the structure thereof is not limited to the above example, and various modifications and changes can be made.

[0036]

[Effect of the Invention] By the small spacing of the mirror surface according to the present invention as described above, the spacing of the outgoing light L _O of the laser without causing heat interference problems with the conventional multi-beam semiconductor laser In comparison with this, it is possible to significantly reduce the number of laser beams. Therefore, it becomes easy to configure a multi-beam laser with an easy-to-use beam interval according to the optical system and track width. Improve the degree of freedom in design.

Further, as described above, since the surface naturally obtained by crystal growth is used as the 45 ° reflecting mirror,
Compared with a conventional reflecting mirror surface formed by oblique etching or the like, it has excellent flatness and angular accuracy, and an ideal reflected beam with no aberration can be obtained. The manufacturing can be remarkably simplified as compared with the semiconductor laser.

Further, according to the present invention, various arrangements such as a four-beam laser arranged in a square shape, a one-dimensional laser array, etc. can be obtained by appropriately selecting the arrangement of a plurality of lasers and the crystal growth mirror surface. A multi-beam semiconductor laser having the above structure can be formed.

Furthermore, by forming the laser by modulating the focal length of each laser, it can be applied to, for example, a focus servo.

[Brief description of drawings]

FIG. 1 is an enlarged schematic perspective view of an example of a multi-beam semiconductor laser.

FIG. 2 is a schematic enlarged perspective view of an example of a multi-beam semiconductor laser.

FIG. 3 is a schematic enlarged plan view of an example of a multi-beam semiconductor laser.

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

FIG. 5 is a manufacturing process diagram of an example of a multi-beam semiconductor laser.

FIG. 6 is a manufacturing process diagram of an example of a multi-beam semiconductor laser.

FIG. 7 is an explanatory diagram of an application example of a 4-beam laser.

FIG. 8 is an explanatory diagram of an application example of a 4-beam laser.

FIG. 9 is a manufacturing process diagram of an example of a multi-beam semiconductor laser.

FIG. 10 is an explanatory diagram of an application example of a two-beam laser.

FIG. 11 is a schematic enlarged perspective view of an example of a conventional multi-beam semiconductor laser.

FIG. 12 is an enlarged schematic perspective view of an example of a conventional multi-beam semiconductor laser.

FIG. 13 is an explanatory diagram of an example of a multi-beam semiconductor laser.

[Explanation of symbols]

 1 Semiconductor Base 2 Main Surface 3 First Cladding Layer 4 Active Layer 5 Second Cladding Layer 6 Cap Layer 7A End Face 7B End Face 8 Dielectric Protective Layer 9 Regrowth Layer 9A Crystal Growth Mirror Face 9B Crystal Growth Mirror Face

Claims (5)

[Claims] 1. A plurality of lasers having a cavity length in the <001> crystal axis direction are arranged on the main surface of a semiconductor substrate having a {100} crystal surface as a main surface so that respective light emitting end faces face each other. And a crystal growth mirror surface made of a {110} crystal face forming an angle of 45 ° with respect to the main surface is provided between the light emitting end faces so as to face the light emitting end faces. Beam semiconductor laser. 2. The multi-beam semiconductor laser according to claim 1, wherein the number of light beams is two. 3. The multi-beam semiconductor laser according to claim 1, wherein the number of light beams is four. 4. A plurality of lasers for emitting a light beam in at least a first direction along a <001> crystal axis direction are formed on the main surface of a semiconductor substrate having a {100} crystal plane as a main surface. A laser that emits a light beam in a direction opposite to the first direction is formed between the light emitting end faces of the lasers, and the laser faces the light emitting end faces of the lasers. A multi-beam semiconductor laser comprising a crystal growth mirror surface formed of a {110} crystal surface that forms an angle of 45 ° with the main surface. 5. The multi-beam semiconductor laser according to claim 1 or 4, wherein the distance between each of the light emitting end faces and the crystal growth mirror surface is modulated and provided for each laser.