1. Field of the Invention
The present invention relates to a semiconductor laser such as a laser diode and a method of manufacturing such a semiconductor laser, and more particularly to a semiconductor laser suitable for use as a light source in an optical system such as an optical pickup for reading information recorded on a magnetooptical disk or the like and a method of manufacturing such a semiconductor laser.
2. Description of the Prior Art
Optical systems such as optical pickups for reading information recorded on a magnetooptical disk or the like incorporate a semiconductor laser such as a laser diode as a light source. Generally, the semiconductor lasers have a mirror surface formed in a cleavage plane. It is known in the art that light returning from the optical system combined with a semiconductor laser is reflected by a front end surface of the mirror surface and reenters the optical system, causing a variety of noise-induced problems. If the reentry of light from the optical system into the semiconductor laser occurs in a three-spot optical disk pickup, then tracking control is adversely affected.
In order to alleviate the above drawback, it has been proposed to reduce the thickness of the pellet itself of the semiconductor laser for thereby allowing as much of the reentrant light from the optical system as possible to pass behind the semiconductor laser pellet.
However, since a wafer from which semiconductor laser pellets are cut out is also reduced in thickness, the mechanical strength of the wafer is lowered. While semiconductor lasers are being fabricated, they have to be handled with utmost care as they tend to be easily damaged. Therefore, the fabrication process is low in efficiency and suffers a high rate of defective semiconductor lasers in the yield.
According to another proposal, the front end surface of the mirror surface of the semiconductor laser, except for a laser emission area, is coated with a material having a low reflectance or a material having a high absorptance. The process of coating such a material is, however, practically complex and difficult to carry out.