Semiconductor laser device

Details Semiconductor laser device Semiconductor laser device

1998-01-21

2001-02-06

Davie, James W. (Department: 2874)

Coherent light generators

Particular active media

Semiconductor

C372S029011, C372S031000

Reexamination Certificate

active

06185239

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor laser device having a semiconductor laser and a monitor photodetector device for detecting light emitted from the semiconductor laser.
2. Description of the Related Art
A semiconductor laser employs light emitted from one end (front-side end surface) of its cavity as an original output light. In this case, in order to achieve a lower threshold current, i.e., a lower consumed power and higher reliability, reflectivity Rr at the other end (rear-side end surface) of the optical cavity is generally set as high as possible.
However, a general semiconductor laser device employs a so-called rear-monitoring type arrangement in which light emitted from a rear-side end surface of an optical cavity of a semiconductor laser is detected by a photodetector device formed of a photodiode to obtain a monitor signal and an output from the semiconductor laser is controlled based on the monitor signal. In this case, when a sufficient monitor output is desired, since an attempt of increasing the reflectivity Rr at the rear-side end surface of the optical cavity as described above is restricted, the reflectivity Rr at the rear-side end surface of the semiconductor laser of this kind is usually set to about 80% or smaller.
SUMMARY OF THE INVENTION
It is an object of the present invention to solve the above problems by setting reflectivity Rr at a rear-side end surface of an optical cavity of a semiconductor laser device as high as possible.
According to an aspect of the present invention, a monitor photodetector used for controlling an output from a semiconductor laser is formed on a mount where the semiconductor laser is disposed. The photodetector is disposed ahead of an end surface, from which a main beam is irradiated, of the semiconductor laser.
According to the present invention, since a front monitor type arrangement is employed and hence reflectivity Rr at a rear end surface of an optical cavity can be set sufficiently large, e.g., about 100%, i.t., 100% or almost 100%, it is possible to achieve improvement of characteristics of a semiconductor laser such as reduction of a threshold current Ith, a reduced characteristic temperature, improvement of reliability or the like.


REFERENCES:
patent: 4692207 (1987-09-01), Bouadma et al.
patent: 4847846 (1989-07-01), Sone et al.
patent: 5191590 (1993-03-01), Kuindersma et al.

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