JPH0728083B2 - Semiconductor laser device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a semiconductor laser device having a high output.

[Prior art]

Generally, as a method of increasing the output of a semiconductor laser, the cavity is enlarged and the protective film on the emitting end face is prevented from being deteriorated. Although each of these methods has some effects, it is difficult to obtain a high output of 10 mW or more at a practical level.

Therefore, it has been attempted to suppress loss due to light emission and light absorption on the end face by devising the structure of the emission end face, and to increase the output by forming a window structure.

FIG. 5 is a schematic diagram of a conventional product having a window structure. A groove 11a having an inverted trapezoidal cross section is formed on the surface of a substrate 11 such as GaAs from one end surface side to the other end surface side. N-type clad layer 12, active layer 13, P-type clad layer 14, cap layer 15
Are laminated in this order, and when the active layer 13 is energized, light is emitted from the end face of the window structure including the groove 11a.

[Problems to be solved by the invention]

By the way, in the conventional product as described above, when compared with the conventional product having no window region, the light absorption deterioration at the end face is small, but it is not sufficient.

[Means for solving problems]

The present invention has been made in view of the above circumstances, and an object thereof is to provide a semiconductor laser device capable of reducing deterioration of an end face and absorption loss and achieving a significant improvement in output. is there.

A semiconductor laser device of the present invention includes a substrate having a groove in a central portion except a peripheral portion, and a plurality of layers including an active layer formed on the substrate and an optical guide layer adjacent to the active layer. ,
The plurality of layers including the active layer and the light guide layer,
It is characterized in that each of the peripheral portions has a flat and uniform thickness.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to the drawings illustrating the embodiments. FIG. 1 is a perspective view of a semiconductor laser device according to the present invention (hereinafter referred to as the device of the present invention), and FIG. 2 is II-II of FIG.
FIG. 3 is a perspective view of the substrate, in which 1 is a substrate, 2 is an n-type cladding layer, 3 is an active layer, 4 is an optical guide layer, 5 is a P-type cladding layer, and 6 is The cap layer is shown.

As shown in FIG. 3, the substrate 1 is provided with a groove 1a having a rectangular shape in plan view and an inverted trapezoidal cross section along the longitudinal direction at the central portion of the surface except the peripheral portion, and the substrate including this groove 1a. The n-type cladding layer 2, the active layer 3, the optical guide layer 4, the P-type cladding layer 5 and the cap layer 6 described above are crystal-grown in this order on the surface of 1 by an epitaxy method or the like. The n-type clad layer 2 is formed so as to substantially fill the inside of the groove 1a, and is formed to have a substantially uniform thickness in the portion other than the groove 1a.
The height of the surface is slightly lower on the back surface of the groove 1a than on other portions and curved toward the groove 1a side. Therefore, the active layer 3 laminated on the n-type clad layer 2 except the groove 1a. Although the substrate 1 is formed to have a substantially uniform thickness, the surface of the portion corresponding to the groove 1a is slightly curved toward the groove 1a. The light guide layer 4 formed on the active layer 3 has a curved lower surface but a flat surface.

As described above, in the device of the present invention, the active layer 3
The light emitted from the curved portion of the
While being guided to the inside, the light is emitted from the end face of the light guide layer 4 having a large cross-sectional area, and deterioration at the end face is reduced. If the provisional light guide layer 4 does not exist, light will be absorbed by the substrate 1 near the end of the active layer 3. In order to avoid this, the active layer 3 may be flattened without being curved, but if it is flattened, the gain waveguide becomes stronger, the current injection region becomes wider, and the threshold rises, and eventually the high output power is obtained. Result in unfavorable results.

Further, the presence of the light guide layer 4 has an effect of eliminating astigmatism, which is a problem in the conventional window structure laser device. In addition, the ratio x in GaxAl _1-x As showing the composition of each of the n-type cladding layer 2, the active layer 3 and the optical guide layer 4 is different in the central portion of the substrate 1, that is, the portion on the groove 1a and the peripheral portion. The absorption of light at the end face is reduced, and deterioration of the end face is also suppressed.

Next, numerical examples of the present invention will be shown.

As a substrate 1, a groove 1a having a width of 4 μm and a depth of 1.5 μm is formed on the surface of an n-type GaAs substrate, leaving 40 μm at each end in the longitudinal direction, and liquid phase growth is performed on the surface of the substrate 1 including the groove 1a. N-type Ga _0.60 Al _0.40 As cladding layer (Te-doped), Ga _0.92 Al _0.08 As active layer, P-type Ga
_0.92 Al _0.08 As Optical guide layer (Ge-doped), P-type Ga _0.06 Al
_{A 0.40} As clad layer (Ge-doped) and a P-type GaAs cap layer (Ge-doped) were continuously grown. The growth start temperature was 800 ° C.

As a result of measuring the output and threshold value of the semiconductor laser device as shown in FIGS. 1 and 2 configured in this way, the output is 140 m
W, the threshold was 30 mA.

It can be seen that this is a marked improvement in the output of the conventional product of 10 mW, compared with the threshold value.

As a result of investigating the relationship between the current I (mA) and the output L (mW), the result shown in FIG. 4 was obtained. In FIG. 4, the horizontal axis represents current and the vertical axis represents output, and it is clear from this graph that output loss is extremely small.

〔effect〕

A semiconductor laser device of the present invention includes a substrate having a groove in a central portion except a peripheral portion, and a plurality of layers including an active layer formed on the substrate and an optical guide layer adjacent to the active layer. ,
The plurality of layers including the active layer and the light guide layer,
Since each of the peripheral portions has a flat and uniform thickness, the refractive index distribution in the lateral direction at the end face portion becomes uniform.
Therefore, the light generated in the active layer is emitted from the light guide layer having a large cross-sectional area, so that the light output density at the end face becomes small.

As a result, the absorption loss at the end face and the deterioration of the end face are sufficiently reduced, so that the output can be greatly improved.

[Brief description of drawings]

1 is a schematic perspective view of the device of the present invention, and FIG. 2 is a schematic perspective view of FIG.
A sectional view taken along line II-II, FIG. 3 is a schematic view of a substrate in the device of the present invention, FIG. 4 is a graph showing a relation between current and output in the device of the present invention, and FIG. 5 is a schematic perspective view of a conventional device. Is. 1 ... Substrate, 1a ... Groove, 2 ... Clad layer, 3 ... Active layer, 4 ... Optical guide layer, 5 ... Clad layer, 6 ... Cap layer

Claims (1)

[Claims] 1. A substrate having a groove in a central portion except a peripheral portion,
A plurality of layers including an active layer formed on the substrate and a light guide layer adjacent to the active layer, wherein the plurality of layers including the active layer and the light guide layer are provided on the peripheral portion. A semiconductor laser device having a flat and uniform thickness.