JPH04296082A - Surface emitting type laser - Google Patents

Abstract

PURPOSE:To enable a surface emitting type laser to be enhanced over two times as much in gain as a conventional one and lessened in oscillation threshold current. CONSTITUTION:A new active region 3B is additionally provided outside a conventional active region 3A, and a cone-shaped reflective plate 8 is provided so as to enable light rays to pass through the newly provided active region 3B, whereby a surface emitting type laser of this design can be enhanced in gain per pass.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called surface emitting laser among semiconductor lasers, and particularly to a surface emitting laser whose gain is improved.

0002

2. Description of the Related Art FIG. 6 is a cross-sectional view showing a conventional surface emitting laser device. In the figure, 1A and 1B are electrodes, 2 is a contact layer, 3A is an active region having the same planar shape as a light extraction window; 4 is the traveling direction of the light, 5 is the light extraction window,
Usually shaped in a circle. 6 is a cladding, and 7 is a semiconductor substrate.

Next, the operation will be explained. Electrode 1A, 1
Electrons and holes injected from B pass through the contact layer 2 and the semiconductor substrate 7 and recombine in the active region 3A. At this time, the light generated or amplified in the active region 3A travels in the direction 4, is reflected by the electrode 1B and the window 5, and travels back and forth within the device many times.

At this time, the contact layer 2 and the semiconductor substrate 7
Since the active region 3A is made of a material with low light absorption, it is designed so that the gain generated in the active region 3A can exceed the overall loss to the light traveling. However, in the oscillation state, gain and loss are balanced. In addition, active area 3A
The thickness is usually 2 to 3 μm, which is about the same as the carrier diffusion length.

[0005]

[Problem to be solved by the invention] Since the conventional surface emitting laser is constructed as described above, it is impossible to increase the gain by increasing the thickness of the active layer (even if the thickness is thicker than the carrier diffusion length). The problem is that it is difficult to lower the oscillation threshold to the level of a normal laser.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a surface emitting laser that can increase the optical gain and lower the oscillation threshold.

[0007]

[Means for Solving the Problems] A surface emitting laser according to the present invention is provided with a conical reflecting plate in the optical path and a second active layer in a region corresponding to the periphery of the light extraction window to provide a reflective surface. The light reflected by the plate also passes through this second active layer.

[0008]

[Operation] The reflector in this invention also allows light to pass through the second active region provided around the conventional active region, so the active region becomes equivalently thicker and the gain can be doubled compared to the conventional one. .

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a surface emitting laser according to the present invention, and FIG. 2 is a sectional view taken along a line connecting line A'-A'' in FIG.

In FIGS. 1 and 2, 3B is a second active region, and 8 is a light reflecting plate. Other same reference numerals indicate the same or equivalent components as those of the conventional device shown in FIG. In the surface emitting laser as shown in FIG. 2, one of the lights amplified in the active region 3A is reflected by the reflector 8, passes through the second active region 3B while being amplified, is reflected by the electrode 1A, and returns to the original state again. The light passes through the opposite path and is reflected by the light extraction window 5. Further, a part of the light passes through the light extraction window 5 and is emitted to the outside.

[0011] Therefore, the light that has made one round trip passes through the active region and the second active region, and it is possible to obtain a gain approximately twice that of a conventional surface emitting laser. Therefore, the oscillation threshold can also be reduced.

[0012] In the above embodiment, the reflection plate 8 is connected to the electrode 1B.
Although a more protruding shape is shown, it may be located below the electrode 1B as shown in FIG. 3, and the same effect as in the above embodiment can be achieved.

Further, although only one set of reflecting plates 8 is used in the above embodiment, multiple sets may be used as shown in FIG.

In addition, although the electrode 1B is not formed in the part corresponding to the reflection plate 8, it may be formed to cover the part corresponding to the reflection plate 8 as shown in FIG. 5, and the same effect as in the above embodiment can be obtained. play.

[0015]

As described above, according to the surface emitting laser according to the present invention, an active region is provided around the conventional active region, and light is also passed through the surrounding active region using a reflector. Therefore, the gain can be doubled compared to the conventional method, and the oscillation threshold can be lowered.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a surface emitting laser according to an embodiment of the present invention.

FIG. 2 is a sectional view of a surface emitting laser according to an embodiment of the present invention.

FIG. 3 is a sectional view of a surface emitting laser according to another embodiment of the invention.

FIG. 4 is a sectional view of a surface emitting laser according to another embodiment of the invention.

FIG. 5 is a cross-sectional view of a surface emitting laser according to another embodiment of the invention.

FIG. 6 is a cross-sectional view showing a conventional surface emitting laser.

[Explanation of symbols]

1A, 1B electrode 2 Contact layer 3A, 3B First and second active regions 4. Direction of light travel 5. Light extraction window 6 Clad 7 Semiconductor substrate 8. Light reflecting plate

Claims (1)

[Claims] Claim 1: In a surface emitting laser, one of the reflectors of the resonator is made into a conical shape having two or more layers, and a second active layer is provided around the first active layer formed below the light extraction window. . A surface emitting laser, wherein the traveling light is reflected twice or more on the conical side surface of the reflecting mirror and passes through the entire area of the first and second active layers.