JPH1022562A - Semiconductor laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove the deviation of polarization from the reference plane of a package by installing a semiconductor laser to compensate the axial deviation of the polarization of a beam. SOLUTION: A semiconductor laser chip 1 is attached to the main face of a block 5 so that the point of light emission may be positioned at the center of a laser package, and it is made a reference position. In the condition that the semiconductor laser chip 1 is placed on a heat sink 2, the base part 3 of the laser package is installed at the block part 5, being rotated by 3-10 deg. from the vertical direction to the reference position, centering around the point of light emission. Hereby, the deviation of the axis of polarization from the reference plane can be removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device, and more particularly to a semiconductor laser device for compensating for a shift in the polarization direction of a laser beam.

[0002]

2. Description of the Related Art DVD (Digital Video Disk) and C
In order to realize a high-density optical disk such as a DR (write-once compact disk), it is necessary to make the spot diameter of a laser beam used for writing and reading data as small as possible. Therefore, research on a short-wavelength laser capable of focusing a laser beam to a small spot has been actively advanced in recent years.

FIG. 6 shows an example of a short wavelength laser in 1996.
FIG. 3 is a cross-sectional view showing the structure of an AlGaInP / GaAs red semiconductor laser device reported in the Spring Meeting of the Japan Society of Applied Physics (26a-C-11).

In this device, an n-type GaInP buffer layer (having a thickness of 0.3 μm) is formed on an n-type GaAs semiconductor inclined substrate 21.
m) 22, n-type (Al _0.7 Ga _0.3 ) _0.5 InP cladding layer (layer thickness 2 μm) 23, Ga _0.58 In _0.42 P tensile strained quantum well layer (four layers, each layer thickness 75 °) and (Al _0.5 Ga _0.5 )
_An active layer 24 having an undoped quantum well structure in which _0.5 In _0.5 P quantum barrier layers (three layers, each having a thickness of 40 °) are alternately stacked is formed in this order.

On the active layer 24, a flat portion 25a
(Layer thickness 0.1 μm) and a stripe ridge portion in a direction perpendicular to the paper surface (this embodiment has a trapezoidal cross section, a lower width of 4 μm, an upper width of 2 μm, and a height of 0.8 μm).
A p-type (Al _0.7 Ga _0.3 ) _0.5 InP clad layer 25 having 5b is formed. On the stripe ridge portion 25b, a p-type Ga _0.5 In _0.5 P contact layer (layer thickness: 0.2 μm) 26 and n portions connected to the upper portion of the flat portion 25a and the side surfaces of the stripe ridge portion 25b,
Type GaAs current block layer (layer thickness 1 μm) 27 is formed.

A p-type GaAs cap layer (layer thickness: 5 μm) 28 is formed so as to be continuous with the surfaces of the contact layer 26 and the current block layer 27, and an n-type Cr—Sn—Au electrode is formed below the substrate 21. 29 is the cap layer 26
A p-type Cr-Au electrode 30 is formed on the upper part of FIG.

At present, as a substrate of a red semiconductor laser, a substrate which is inclined several degrees in the [011] direction from a (100) plane is generally used. The reason for this is that these inclined substrates suppress the generation of a natural superlattice in the AlGaInP crystal structure, and thus are extremely effective methods for shortening the oscillation wavelength.

FIG. 7A is a top view of a laser package having a conventional structure. The laser chip 1 is incorporated in a laser package via a heat sink 2. In an ordinary laser package, extension lines (X1'-X2 ') of a plurality of horizontal cutouts 4 provided on a base portion 3 serving as a reference surface of the package so that positioning at the time of mounting an optical pickup can be performed easily. The main surface of the block portion 5 on which the heat sink 2 is placed is mounted horizontally.

[0009]

However, FIG.
As shown in (b), the polarization axis (AB) of the semiconductor laser chip using the tilted substrate is slightly shifted as compared with the just substrate having no tilt. The axis is also a vertical reference axis (Y1'-
Y2 ').

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a semiconductor laser device having no polarization axis deviation from a reference surface of a package.

[0011]

According to a semiconductor laser device of the present invention, a semiconductor laser device formed on a semiconductor substrate having a main surface having a plane inclined in the direction of a certain crystal axis is provided. It is characterized in that it is installed so as to compensate for axis deviation.

In this case, since the angle of deviation of the polarization axis can be compensated, in an optical system such as an optical disk,
The laser beam can be polarized in a desired direction, and the jitter of the reproduction characteristics is improved.

In particular, the semiconductor laser is a TM mode laser having a tensile strained multiple quantum well layer in an active layer,
The semiconductor laser is characterized by being installed in a counterclockwise direction within a range of 3 to 10 degrees around a laser emission point with respect to a reference position.

In this case, since the deviation angle of the polarization axis of the TM mode laser can be compensated, the laser beam can be polarized in a desired direction in an optical system such as an optical disk, and the jitter of the reproduction characteristics is improved. .

In particular, the semiconductor laser is a TM mode laser having a tensile strained multiple quantum well layer in an active layer,
The semiconductor laser is characterized by being installed in a counterclockwise direction within a range of 5 to 7 degrees around a laser emission point with respect to a reference position.

In this case, since the deviation angle of the polarization axis of the TM mode laser can be better compensated, the laser beam can be polarized in a certain reference direction in an optical system such as an optical disk, and the jitter of the reproduction characteristic is reduced. Be improved.

In particular, the semiconductor laser is a TM mode laser having a tensile strained multiple quantum well layer in an active layer,
The semiconductor laser is moved 3 to 1 in a counterclockwise direction from a reference position.
It is characterized by being installed on a base inclined at an angle of 0 degrees.

In this case, since the deviation angle of the polarization axis of the TM mode laser can be compensated, the laser beam can be polarized in a desired direction in an optical system such as an optical disk, and the jitter of the reproduction characteristics is improved. .

In particular, the semiconductor laser is a TM mode laser having a tensile strained multiple quantum well layer in an active layer,
The semiconductor laser is moved 5-7 counterclockwise from the reference position.
It is characterized by being installed on a pedestal that is inclined within a range of degrees.

In this case, since the deviation angle of the polarization axis of the TM mode laser can be compensated, the laser beam can be polarized in a desired direction in an optical system such as an optical disk, and the jitter of the reproduction characteristics is improved. .

In particular, the semiconductor laser is a TE mode laser having a compression-strained multiple quantum well layer in an active layer, and the semiconductor laser is at an angle of 2 to 3 degrees with respect to a reference position with respect to a laser emission point. It is characterized by being installed clockwise in a range.

In this case, since the deviation angle of the polarization axis of the TE mode laser can be compensated, the laser beam can be polarized in a desired direction in an optical system such as an optical disk, and the jitter of the reproduction characteristics is improved. .

In particular, the semiconductor laser is a TE mode laser having a compression-strained multiple quantum well layer in an active layer, and the semiconductor laser is tilted clockwise in a range of 2 to 3 degrees with respect to a reference position. It is characterized by being installed above.

In this case, since the deviation angle of the polarization axis of the TE mode laser can be compensated, the laser beam can be polarized in a desired direction in an optical system such as an optical disk, and the jitter of the reproduction characteristics is improved. .

In particular, the pedestal is a block.

In this case, the block portion is inclined.

In particular, the pedestal is a heat sink.

In this case, the heat sink is inclined.

Particularly, when the semiconductor laser is AlGaInP
It is a semiconductor laser.

In this case, it is effective for a short wavelength laser having a wavelength of 650 to 680 nm.

In particular, the present invention is characterized in that the semiconductor laser is formed on a semiconductor substrate having a main surface having a surface inclined in the [011] direction from the (100) plane.

In this case, it is effective for a short wavelength laser having a wavelength of 630 to 660 nm.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A according to a first embodiment of the present invention, A
An lGaInP-based semiconductor laser device will be described with reference to the drawings. 1 (a) and 1 (b) are a top view of a laser package according to the present invention and a diagram showing a polarization direction of a laser beam, respectively.

In FIG. 1A, a semiconductor laser chip 1 has a TM having a tensile strained multiple quantum well layer in an active layer.
This is a mode (the electric field component is perpendicular to the traveling direction) laser, and is mounted on the heat sink 2 with the bonding surface facing down in the laser package.

In a normal laser package, there are a plurality of horizontal cutouts 4 provided in a base portion 3 serving as a reference surface of the laser package so that positioning at the time of mounting an optical pickup can be easily performed. X1-X2;
The main surface of the block portion 5 on which the heat sink 2 is placed is
Mounted horizontally. The semiconductor laser chip 1 is mounted horizontally on the main surface of the block section 5 and its light emitting point is located at the center of the laser package, and this is used as a reference position.

However, in the semiconductor laser chip 1 having the inclined substrate installed as shown in FIG. 1A, the laser beam emitted from the back of the paper toward the front is polarized in the direction perpendicular to the paper. However, in practice, 3 to 10 degrees clockwise around the light emitting point (typical value: 5 to 7).
Since the polarization axis shifts in the range of (degree), desired reproduction / recording characteristics cannot be obtained when used in an optical pickup optical system.

Therefore, with the semiconductor laser chip 1 mounted on the heat sink 2, the base part 3 of the laser package is connected to the block part 5 in order to compensate for the polarization axis deviation angle θ of the semiconductor laser chip 1. In the clockwise direction from the vertical direction of the reference position around the light emitting point.
It is installed after being rotated by 10 to 10 degrees, preferably 5 to 7 degrees.
This may be done by rotating the block 5 counterclockwise with respect to the base 3, and may be solved by any method. Then, as shown in FIG. 1B, a laser beam having no polarization axis deviation with respect to the X1-X2 and Y1-Y2 axes determined by the horizontal cutout 4 and the vertical cutout 6 of the package is obtained.

FIG. 2 shows an external view of a semiconductor laser device according to a second embodiment of the present invention. The same effect can be obtained even when the semiconductor laser 1 is installed on the inclined block portion 5 for compensating the axis deviation angle of the polarization direction of the laser beam. That is, the semiconductor laser chip 1 is mounted on the block portion 5 inclined at 3 to 10 degrees, preferably 5 to 7 degrees in the negative direction about the light emitting point with respect to the horizontal direction of the reference position. As a result, a laser beam polarized in a direction perpendicular to the paper surface is obtained. In this case, the semiconductor laser chip 1
Is rotated with the horizontal cutout 4 as a reference.

FIG. 3 shows an external view of a semiconductor laser device according to a third embodiment of the present invention. The same effect can be obtained even if the semiconductor laser 1 is mounted on the inclined heat sink 2 for compensating for the angular deviation in the polarization direction of the laser beam.
That is, with respect to the horizontal direction of the reference position, the semiconductor laser chip 1 is rotated counterclockwise by 3 to 10 degrees around the light emitting point,
Preferably, a laser beam polarized in a direction perpendicular to the paper is obtained by installing the heat sink 2 at an inclination of 5 to 7 degrees.

In the present invention, [011]
As a result of measuring the polarization direction of a semiconductor laser having a strained multiple quantum well structure in the active layer formed on a semiconductor substrate having a plane inclined by several degrees in the main direction, the multiple quantum well of the semiconductor laser was obtained. It was found that the magnitude of the angle of the polarization axis shift and the direction of the shift differ depending on the strain direction (tensile strain or compressive strain) of the layer active layer.

First, in a semiconductor laser device having a wavelength of 635 nm, a tensile-strained multiple quantum well layer was introduced into an active layer using a substrate whose main surface had a surface inclined several degrees in the [011] direction from the (100) plane. In this case, a TM mode laser is used. The polarization direction of this laser element is as shown in FIG.
It is found that the axis is shifted clockwise with respect to the vertical direction with respect to the active layer, and the degree of the axis shift is shifted by +5 to 6 ° when the substrate tilt angle is in the range of 7 to 13 °.

On the other hand, in a semiconductor laser device having a wavelength of 635 nm, a multiple quantum well layer having a compressive strain is introduced into the active layer by using a substrate having a main surface having a plane inclined several degrees in the [011] direction from the (100) plane. In this case, a TE mode laser is obtained. The polarization direction of this laser element is as shown in FIG.
Unlike the TM mode laser, the active layer is shifted counterclockwise with respect to the horizontal direction with respect to the active layer, and the substrate tilt angle is 7 °.
In the range of で は 13 °, it was found that the angle was as small as −2 ° or less.

FIG. 5 summarizes these measurement results. In this figure, the horizontal axis shows the inclination angle of the substrate, and the vertical axis shows the deviation angle of the polarization axis. From these results, it is possible to obtain a TM mode for tensile strain and a TE mode for compressive strain due to the difference in strain introduced into the multiple quantum well layer of the active layer. , + 5-6 ° and -2 ° or less.

As can be seen from the above measurement results, the TM mode laser having the tensile strained multiple quantum well layer in the active layer described in the first to third embodiments of the present invention, and the multiple strain of the compressive strain in the active layer. The deviation direction and angle of the polarization axis are different from those of the TE mode laser in which the quantum well layer is introduced. Therefore,
Regarding the TE mode laser, the absolute value of the rotational direction is opposite to that of the embodiment of the TM mode laser of the present invention.
It is applied by replacing the angle to に 3 °, and a laser beam free from a deviation of the polarization axis in a direction parallel to the paper surface can be obtained by the same effect as in the above embodiment.

That is, with respect to the first embodiment of the present invention, the semiconductor laser chip 1 is installed by being rotated counterclockwise by two to three degrees from the horizontal direction of the reference position around the light emitting point of the semiconductor laser chip 1. . This may be achieved by installing the block unit 5 by rotating the block unit 5 clockwise with respect to the base unit 3, or may be solved by any method.

Next, in the second embodiment of the present invention, the semiconductor laser chip 1 is inclined by 2 to 3 degrees in the positive direction with respect to the light emitting point with respect to the horizontal direction of the reference position. It is installed on the block unit 5.

Further, in the third embodiment of the present invention, the heat sink in which the semiconductor laser chip 1 is inclined by 2 to 3 degrees in the positive direction with respect to the light emitting point with respect to the horizontal direction of the reference position. 2, a laser beam polarized in a direction parallel to the plane of the paper can be obtained.

In the above embodiment, the active layer of the semiconductor laser has a multiple quantum well structure, but may have a single quantum well structure or an active layer that is a non-quantum well layer.

In the above embodiment, a semiconductor laser device having a stripe-shaped ridge portion has been described. However, the present invention is directed to a semiconductor laser device having a main surface having a surface inclined in the [011] direction from a (100) plane. The present invention is also applicable to semiconductor lasers having any of the above structures.

In the above description, the AlGaInP-based semiconductor laser device has been described.
The present invention can be applied to 1GaAs and InGaAs semiconductor laser devices as appropriate.

[0051]

According to the present invention, [0]
11] In a semiconductor laser formed on a semiconductor substrate having a main surface inclined in the direction, a semiconductor laser device having no deviation of a polarization axis from a reference surface of a package can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an external view of a semiconductor laser device according to a first embodiment of the present invention and a diagram illustrating a polarization direction of a laser beam.

2A and 2B are an external view of a semiconductor laser device according to a second embodiment of the present invention and a diagram illustrating a polarization direction of a laser beam.

3A and 3B are an external view of a semiconductor laser device according to a third embodiment of the present invention and a diagram illustrating a polarization direction of a laser beam.

FIG. 4 is a schematic diagram showing a difference in polarization axis shift direction between a TM mode laser and a TE mode laser in a semiconductor laser formed on an inclined substrate.

FIG. 5 is a diagram showing a relationship between a tilt angle and a polarization axis shift angle in a semiconductor laser formed on a tilted substrate.

FIG. 6 is a sectional view showing the structure of an AlGaInP / GaAs red semiconductor laser device having a conventional structure.

FIG. 7 is a schematic diagram showing a conventional laser package and a polarization axis shift.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor laser chip 2 Heat sink 3 Laser package base part 4 Horizontal cutout part 5 Block part 6 Vertical cutout part

Claims (11)

[Claims] 1. A semiconductor laser device formed on a semiconductor substrate having a main surface having a plane inclined in a certain crystal axis direction, wherein the semiconductor laser is installed so as to compensate for an axis shift in a beam polarization direction. Characteristic semiconductor laser device. 2. The semiconductor laser according to claim 1, wherein said semiconductor laser is a TM mode laser having a tensile strained multiple quantum well layer in an active layer. 2. The semiconductor laser device according to claim 1, wherein the semiconductor laser device is installed so as to rotate counterclockwise. 3. The semiconductor laser according to claim 1, wherein said semiconductor laser is a TM mode laser having a tensile strain multiple quantum well layer in an active layer. 2. The semiconductor laser device according to claim 1, wherein the semiconductor laser device is installed so as to rotate counterclockwise. 4. The semiconductor laser according to claim 1, wherein the semiconductor laser is a TM mode laser having a tensile strained multiple quantum well layer in an active layer, and the semiconductor laser is mounted on a base inclined in a range of 3 to 10 degrees counterclockwise from a reference position. 2. The semiconductor laser device according to claim 1, wherein 5. The semiconductor laser according to claim 1, wherein said semiconductor laser is a TM mode laser having a tensile strained multiple quantum well layer in an active layer, and said semiconductor laser is mounted on a base inclined in a range of 5 to 7 degrees counterclockwise from a reference position. 2. The semiconductor laser device according to claim 1, wherein 6. The semiconductor laser according to claim 1, wherein said semiconductor laser is a TE mode laser having a compression-strained multiple quantum well layer in an active layer. 2. The semiconductor laser device according to claim 1, wherein the semiconductor laser device is rotated clockwise. 7. A pedestal wherein said semiconductor laser is a TE mode laser having a compression-strained multiple quantum well layer in an active layer, wherein said semiconductor laser is inclined clockwise within a range of 2 to 3 degrees with respect to a reference position. 2. The semiconductor laser device according to claim 1, wherein the semiconductor laser device is installed in a semiconductor device. 8. The semiconductor laser device according to claim 4, wherein said pedestal is a block portion. 9. The semiconductor laser device according to claim 4, wherein the pedestal is a heat sink. 10. The semiconductor laser according to claim 1, wherein said semiconductor laser is an AlGaInP-based semiconductor laser.
10. The semiconductor laser device according to 3, 4, 5, 6, 7, 8, or 9. 11. The semiconductor laser according to claim 1, wherein said semiconductor laser is formed on a semiconductor substrate having a main surface having a surface inclined in a [011] direction from a (100) plane.
The semiconductor laser device according to 5, 6, 7, 8, 9, or 10.