JPS63318183A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To prevent an outgoing beam from having an eclipse and an irregular reflection by a method wherein a recessed part with a side face slanted against a laser ray outgoing end face is formed adjacent thereto. CONSTITUTION:A recessed part with a side face 5 slanted against a laser ray outgoing end face is formed adjacent to the outgoing end face of a semiconductor substrate 1 so as to protect a radiated laser ray against deterioration. The position of the recessed part is so determined as to satisfy such an equation as S<=d/tanalpha, where S denotes the step length of the base of the laser ray outgoing end face, (d) is the distance to an active layer, and an angle alpharepresents the angle at which the intensity of the laser ray becomes 1/10 times as small as the peak intensity in a ray radiating property. The laser being structured as mentioned above, the radiated laser beam is prevented from an eclipse and an irregular reflection.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a semiconductor laser in which an optical resonator reflecting surface is formed by a dry etching method, a wet etching method, etc.
This invention relates to a structure for countermeasures against returning light.

[Prior art] Semiconductor lasers have excellent characteristics such as small size and high efficiency.
It has come to be increasingly applied to light sources for optical disk pickups, etc. The optical resonator of a semiconductor laser is generally constructed by a cleavage plane that utilizes a specific orientation of a crystal. This cleavage step has low workability in the semiconductor laser device manufacturing process, which is disadvantageous for mass production.

In contrast, in relatively recent years, attempts have been made to actively form the reflective surface of a semiconductor laser by wet etching or dry etching.

According to these methods, the workability of the semiconductor laser device manufacturing process is significantly improved, and mass production becomes easier.

For the method of fabricating a resonator by the above-mentioned etching, see, for example, the Proceedings of the Japan Society of Applied Physics, p.

96 (Autumn 1983).

[Problem that the invention seeks to solve]

It has become clear that the above-mentioned conventional technology does not take into account light emission characteristics or reflected return light, and has the following problems.

Problem 1 When producing a reflective surface by dry etching or the like, the etching is usually performed to a depth of about 1 μm to several μm deeper than the laser active layer. - The light beam of the oyster conductor laser is normally emitted with a spread of about 20° to 40° in the vertical direction. As a result, a portion of the laser beam is reflected at the bottom of the etched area, significantly affecting the light emission characteristics.The way to solve this problem is to make the etching deep enough to prevent reflection. It is possible to reduce the effect, but in reality, if etching is continued to a sufficient depth, the flatness and smoothness of the resonator reflection surface will be impaired.

Problem 2: Also, in optical disks, which is an application field of semiconductor lasers, one of the tracking methods is to divide the laser beam into three spots using a diffraction grating and extract the tracking signal from the two laser spots on both sides. . In optical disk systems.

Both laser and disk surface are in focus position Uses an optical system that sets Therefore, it is connected to three points on the above optical disk. The imaged laser beam is reflected and split into half. An image is formed on the end face of the conductor laser. On this occasion, The surface on which the above reflection spot returns is The resonator is formed by a surface parallel to the reflective surface. If it is, it will be reflected by the laser section again. on the disc surface or the light receiving system. Noise in the tracking signal There was a problem in that it was easy to cause

The purpose of the present invention is to solve the above problems. The structure of a semiconductor laser device that solves It is about providing.

[Means for solving problems]

In order to achieve the above object, the present invention is designed to prevent the emitted laser light from being obstructed near the output end face of the semiconductor laser substrate in which an optical resonator is formed by etching or the like, as shown in FIG. 1(a). A structure is used in which a concave portion is further provided, and the surface constituting the concave portion is non-parallel to the resonator reflecting surface.

For the position of this recess, the length of the step at the bottom of the laser beam emission surface is S, the distance to the active layer is d, and the angle at which the intensity is 1/1o from the peak position of the laser light emission characteristic is α. Time (Figure 1(a).

(b)), it is preferable that approximately the following formula is satisfied.

S≦□ tan α For example, when d = 3 p m and a = 30'', S is approximately 5.2 μm or less.

[Effect]

FIG. 1(a) shows the area near the semiconductor laser light emitting part.

In the cross-sectional view in the direction of light propagation, 1 is a semiconductor substrate crystal;
2 is a laser active layer, 3 is a resonator reflecting surface, 4 is a step at the bottom of the reflecting surface, and 5 is a side surface of the recess.

According to this structure, the recess provided near the resonator reflecting surface formed by etching or the like eliminates vignetting and diffuse reflection of the emitted laser beam, and the light emission characteristics of the semiconductor laser are significantly improved.

Also in optical disk applications. Since the returned light of the tracking beam is reflected by the slope of the side surface 5 of the recess in a direction that prevents it from entering the optical system between the laser disks again, tracking errors, which have been a problem in practical applications, can be significantly improved.

〔Example〕

Examples of the present invention will be described below with reference to FIGS. 2(a) and 2(b). FIG. 2(a) is a perspective view of a semiconductor laser device according to an embodiment of the present invention, in which a resonator reflection surface is formed by etching, and FIG. 2(b) is a sectional view thereof. b is n
Type G, aAs substrate ((100) plane) with GaAs on top of it.
- A laser structure crystal 7 having a GaAlAs multilayer structure is formed. C3 is used for the laser transverse mode control method.
P (Channel 5ubstrate Plan)
ar) structure was used. 8 is a p-side electrode, and 9 is an n-side electrode. The resonator reflecting surface 3 was processed and formed almost vertically by reactive ion beam etching. The depth is approximately 7 μm.

Reference numeral 10 denotes a concave portion, which is an important point in the present invention, and was formed at a position of about 3 μm from the reflecting surface 3 and at a depth of about 55 μm from the laser active layer 2. To process this recess, a reaction rate-limiting etchant based on phosphoric acid and hydrogen peroxide is used to process the recess.
The side surface 5 constituting 0 is made non-parallel to the laser cavity reflecting surface 3.

This point is an important point of the present invention. In this embodiment, the side faces 5 of the recess 10 are at β~35° and γ~35° with respect to the reflective surface 3, respectively.
20" tilted, (111) Ga plane and (221
) surface.

The semiconductor laser device of the present invention has an oscillation threshold current of approximately 6Q.
It oscillated at mA and a wavelength of about 790 nm. In addition, the recess 10 provided near the laser emitting part 11 prevented part of the laser beam from being vignetted or diffusely reflected, so the 0-beam laser, which had good light emission characteristics, was applied to an optical disk pickup. This is due to the effect of the side surface 5 of the recess 10 being formed obliquely to the laser reflecting surface 3.

It has been found that good tracking characteristics can be obtained because the tracking beam can be prevented from being re-reflected.

It has been experimentally confirmed that there is no problem as long as the inclination of the side surface 5 with respect to the reflective surface 3 is 8.3 degrees or more.

〔Effect of the invention〕

According to the present invention, the emitted beam is prevented from being vignetted by the recess provided in the vicinity of the light emitting end face of the semiconductor laser probe in which the resonator reflecting surface is formed by etching or the like.

Diffuse reflection can be prevented and the light emission characteristics of the laser device can be significantly improved. In addition, by configuring the side surfaces of this recess with non-parallel surfaces inclined at 8.3 degrees or more with respect to the resonator reflection surface, and by setting the depth to 50 μm or more from the laser active layer,
When applied to optical discs, multiple reflections of the tracking beam can be prevented and the tracking characteristics can be significantly improved, which is extremely effective.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are a sectional view of the semiconductor laser device of the present invention in the vicinity of the reflecting surface in the direction of light propagation, and a light emission characteristic diagram, respectively, and FIG. 2(a). (b) is an oblique view and a cross-sectional view of a semiconductor laser device according to an embodiment of the present invention, respectively. DESCRIPTION OF SYMBOLS 1... Semiconductor crystal substrate, 2... Laser active layer, 3...
...Resonator reflecting surface, 4...Reflecting surface bottom step, 5.
・・Side surface of the recess, 6 ・N-type GaAs substrate, 7
. . . Laser structure crystal, 10 . . . Concave portion, 11 .

Claims (1)

[Claims] 1. In a semiconductor laser whose laser light emitting end face is formed by etching, a recessed portion having a side surface inclined with respect to the laser light emitting end face is provided in the vicinity of the laser light emitting end face of the substrate of the semiconductor laser. A semiconductor laser characterized in that: 2. The semiconductor laser according to claim 1, wherein the depth of the recess is 50 μm or more from the laser light emitting part.