JPH1140885A - Semiconductor laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve uniformly of a near-field pattern by a method, wherein a primary diffraction grating is provided on each side of the current injection strips region of an active layer which extends in the surface of the active layer and vertical to the lengthwise direction of a resonator. SOLUTION: In a semiconductor laser device, a primary diffraction grating 19 is provided on each side of a current injection stripe region in a GaAs active layer 3, extending in the surface of the active layer 13 and vertical to the lengthwise direction(direction vertical to both cleavage plates) of a resonator. The primary diffraction grating 19 is formed so as to reduce an angle π of incidence at which light traveling towards the sides of the stripe-like current injection region of the GaAs active layer 13 is totally reflected. Therefore, a lateral mode on each side of the stripe-like current injection region is turned to a higher order by the firstorder diffraction grating 19. Through this setup, a lateral mode of high order can be positively used, and the semiconductor laser device is capable of obtaining a uniform near-field pattern and enhanced in output.

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 suitable for a high-output type used in the field of manufacturing optical disks and the like.

[0002]

2. Description of the Related Art A semiconductor laser device is usually formed of GaAs / Al using an MBE device (molecular beam epitaxy device) or a MOCVD device (metal organic chemical vapor deposition device).
It is manufactured by uniformly growing a crystal of a material such as GaAs or InP / InGaAsP.

[0003]

However, conventionally, it is actually difficult to grow crystals uniformly,
Therefore, it is inevitable that a slight non-uniformity occurs in the crystal. As a result, the conventional semiconductor laser device has a problem that the near-field image becomes non-uniform.

[0004] In view of the above, an object of the present invention is to provide a semiconductor laser device in which the near field image uniformity is improved.

[0005]

In order to achieve the above object, in a semiconductor laser device according to the present invention, a current injection stripe region of an active layer is formed in a direction in a layer plane and a direction perpendicular to a cavity length direction. It is characterized in that primary diffraction gratings are provided on both sides.

Since the thickness of the active layer is usually about 1 μm to several μm, the transverse mode is a single mode in the layer thickness direction. However, both sides of the current injection stripe area,
In other words, in the direction in the layer plane and at right angles to the cavity length direction, the width of the stripe region is 10 μm to several tens μm, so that the transverse mode is not a single mode. If a primary diffraction grating is provided on both sides of the stripe region to reduce the angle of total reflection, the transverse mode can be made higher. In this way, the near-field image can be made uniform and the output can be increased by actively utilizing the higher-order transverse mode.
This means that the width of the current injection stripe region should be 100 μm or less.
This is particularly effective in a high-output type semiconductor laser device expanded to several 100 μm.

[0007]

Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an embodiment in which the present invention is applied to a high-output type semiconductor laser device having a structure called a window structure. In FIG. 1, an n-AlGaAs cladding layer 12, a GaAs active layer 13, an n-AlGaAs cladding layer 14, and an insulating layer 15 such as silicon dioxide are sequentially grown on the surface of an n-GaAs substrate 11. . An opening is provided in the insulating layer 15, and impurities such as Zn are diffused through the opening to form a striped p − region 17 into the n-AlGaAs cladding layer 14.
And a p-electrode layer 16 is formed thereon. On the back side of the n-GaAs substrate 11, n-
An electrode layer 18 is formed.

In this semiconductor laser device, n-AlGa
The current injection region is limited by the striped p-region 17 formed in the As cladding layer 14, and current confinement using a reverse-biased pn junction is performed. Then, the striped p-regions 17 form two mirror-like cleaved end faces forming an optical resonator (the front and back sides of the hand in the figure).
In such a case, a window region having a wide forbidden band is provided near the end face, and a non-excitation area with less absorption of the laser beam is provided near the end face to achieve high output.

In such a semiconductor laser device, G
A first-order diffraction grating 19 is provided on both sides of the stripe-shaped current injection region of the aAs active layer 13, that is, in a direction in the plane of the layer and at right angles to the resonator length direction (direction between both cleavage planes). I have. The primary diffraction grating 19 is, for example, Ga
After the crystal growth of the As active layer 13, it can be formed by performing masking, exposure, and selective etching using a photolithography technique.

Then, as shown in FIG. 2, the first-order diffraction grating 19 is formed such that the incident angle θ at which light traveling in both sides of the stripe-shaped current injection region of the GaAs active layer 13 is totally reflected becomes small. I do.

Therefore, the first-order diffraction grating 19
The lateral mode in both sides of the stripe-shaped current injection region of the GaAs active layer 13 has a higher order. As a result, a higher-order transverse mode can be positively used, a uniform near-field image can be obtained, and high output can be achieved. In particular, p-electrode layer 16 and striped Zn
By increasing the width of the diffusion p-region 17, GaAs
The width of the current injection stripe region of the active layer 13 is 100 μm
This is effective when the output is increased to about 100 μm to increase the output.

The above description is for one embodiment of the present invention, and it is a matter of course that the present invention is not limited to this embodiment. The structure of the semiconductor laser device to be applied is not limited to the window structure as described above, and the material may be not only GaAs / AlGaAs-based material but also other materials such as InP / InGaAsP-based material. The structure for current confinement is not limited to the above, but may be another structure such as a buried type (BH type). Further, a quantum well structure other than the double hetero structure may be employed.

[0013]

As described above, according to the semiconductor laser device of the present invention, the uniformity of the near-field image can be improved and the output can be increased by increasing the order of the transverse mode.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing light traveling in both sides of a stripe-shaped current injection region in an active layer.

[Explanation of symbols]

 Reference Signs List 11 n-GaAs substrate 12 n-AlGaAs cladding layer 13 GaAs active layer 14 n-AlGaAs cladding layer 15 2 silicon oxide insulating layer 16 p-electrode layer 17 Zn diffusion stripe p-region 18 n-electrode layer 19 primary diffraction grating

Claims (1)

[Claims] 2. A semiconductor laser device comprising: a first-order diffraction grating provided on both sides of a current injection stripe region of an active layer in a direction in a plane of a layer and perpendicular to a longitudinal direction of a resonator.