JPH01256189A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To stabilizes the amount of projection light by inclining a projection window of laser beam and by controlling projection power of laser according to the light amount which is received at a PIN diode arranged at the side. CONSTITUTION:A laser chip 3 is fixed to a post 2 on a base 1 and front projection light 10 is projected from an upper edge surface of the laser chip 3. A projection window 21 is arranged aslant to an optical axis and its angle depends on a thickness of the projection window 21 and an astigmatic difference of a laser. The beam reflected at the projection window 21 incidents to a PIN diode 6 which is fixed to a PIN diode post 22 at the side and the beam reflected at a surface of the PIN diode 6 returns to the laser chip 3, resulting in the reduction of noises. The amount of projection light from a laser can be stabilized in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention can be used in the fields of optical discs such as compact discs CDs, laser discs LDs, recordable optical discs, and erasable optical discs, as well as in the fields of communications, laser printers, etc. The present invention relates to semiconductor lasers.

Background of the Invention In recent years, the fields in which semiconductor lasers are used have expanded, and they are used in optical discs such as CDs, LDs, write-once optical discs, and erasable optical discs, communications, and laser printers. There is. Furthermore, high-power semiconductor lasers are becoming necessary for write-once and erasable types.

In a conventional semiconductor laser, as shown in FIG. 3, a post 2 is attached to a base 1, and a laser chip 3 is fixed to the tip of the post 2. The diffused light emitted from the front end face of the laser chip 3 passes through the window 6 and is output. window 5
is fixed to the cap 4, and the laser chip 3 is sealed. A PIN diode 6 placed at a position where the light emitted from the rear end face of the laser chip 3 detects the power of the light emitted from the laser chip 3, and by applying non-feedback to the laser, it is possible to detect the power of the light emitted from the front end face. Control the emitted light.

FIG. 4 shows a method of controlling the light emitted from the front end face. The rear emitted light 11 of the semiconductor laser 8 is received by the PIN diode 9, converted into a current, and then input to the amplifier 12. Also,
A reference voltage 13 determined from the characteristics of the semiconductor laser 8 and the necessary output power is applied to the laser driving power circuit 14 to drive the laser.

Problems to be Solved by the Invention However, conventional semiconductor lasers cannot reduce the astigmatism difference that the laser itself has.

■ Since the output light of the laser is controlled by the light emitted from the rear end facet, the phases of the emitted light from the front end face and the light emitted from the rear end face are different.

■ Due to the placement of the PIN diode, the laser chip is located far from the base, resulting in a low heat dissipation coefficient.

There was a problem.

In problem (2), astigmatism occurs in the beam converged by another lens provided in the optical path. Problem (3) does not allow optimal output control. Problem (3) is disadvantageous to increasing the output power of lasers.

The present invention provides a semiconductor laser that reduces or solves the above problems.

Means for Solving the Problems In order to solve the above problems, the semiconductor laser of the present invention has a beam exit window that is arranged obliquely to the optical axis of the laser, and the light emitted from the laser is reflected by the beam exit window. let me,
The reflected beam is received by a PIN diode placed next to the laser chip, and the amount of light emitted from the laser is stabilized by controlling the current supplied to the laser based on the amount of received light. be.

Operation The present invention reduces or solves the above-mentioned problems (1) to (3) by using the above-described configuration.

As a method to solve the problem (2), arranging the beam exit window obliquely with respect to the optical axis of the beam can reduce the astigmatism difference of the laser.

As a method to solve the problem (1), since the light emitted from the front end surface that is actually used is used, the emitted light of the laser can be optimally controlled.

As a solution to the problem (2), since there is no PIN diode at the bottom of the laser chip, the laser chip can be placed as close to the base as possible, which increases the heat dissipation coefficient and makes it easier to increase the output of the laser.

EXAMPLE Hereinafter, a semiconductor laser according to an example of the present invention will be described with reference to the drawings. FIG. 1 shows the configuration of a semiconductor laser in an embodiment of the present invention.

A laser chip 3 is fixed to a post 2 on a base 1, and a front side emitted light 1o is emitted from an upper end face of the laser chip 3. The exit window 21 is arranged obliquely to the optical axis, and its angle is determined by the thickness of the exit window 21 and the astigmatism difference of the laser.The exit window 21 is provided in the cap 20, and the cap 2o is fixed to the base. By doing so,
Laser Sentsubu 3 is sealed.

The beam reflected by the exit window 21 enters the PIN diode 6 fixed to the PIN diode post 22 on the side. By making the angle of the PIN diode 6 oblique to the incident optical axis, the problem that the beam reflected on the surface of the PIN diode 6 returns to the laser chip 3 and increases noise is reduced.

FIG. 2 shows a method of controlling the emitted light. A portion of the front-side emitted light 1o from the laser 8 is received by the PIN diode 6, and is converted into a current, amplified by the amplifier 12, and input to the laser drive circuit 14. Further, a reference voltage 13 determined from the characteristics of the semiconductor laser 8 and the required output power is applied to the laser driving power circuit 14 to drive the laser.

Effects of the Invention As described above, the present invention has an oblique exit window for the laser beam, and controls the output power of the laser according to the amount of light reflected by the exit window received by the PIN diode disposed on the side. , the astigmatism difference of the laser itself can be reduced, and since the front side emitted light of the laser is used, the output light can be controlled optimally.
Since there is no IN diode, the distance between the laser chip and the base is shortened, improving the heat dissipation effect and making it possible to increase the output of the laser. Another advantage is that the light-receiving surface of the PIN diode is parallel to the optical axis, so it is less susceptible to stray light from the outside, and the laser output power can be controlled with high precision. It also has the feature that the reflectance of the rear end face can be made 100%, so that the luminous efficiency can be improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a semiconductor laser according to an embodiment of the present invention, FIG. 2 is a block diagram showing a method for controlling the emitted light of the semiconductor laser, and FIG. 3 is a sectional view showing a conventional semiconductor laser. FIG. 4 is a block diagram showing a conventional method for controlling light emitted from a semiconductor laser. 1...Base, 3...Laser chip 7
', 4.20... Cap, 5,21...
...Exit window, 6...PIN diode. Name of agent: Patent attorney Toshio Nakao and 1 other person1-
(-s2-ff, '7-to5-z digit 6--the lN die χ-Y 7-hand

Claims (2)

[Claims] (1) The beam exit window of the semiconductor laser case that seals the semiconductor laser chip is composed of a parallel flat plate, and this parallel flat plate is arranged obliquely to the optical axis, so that the emitted light from the semiconductor laser chip is reflected by the parallel flat plate. A semiconductor laser characterized in that a photodetector is placed at a position where a photodetector is placed. (2) The semiconductor laser according to claim 1, wherein the light receiving surface of the photodetector is arranged obliquely with respect to the optical axis of the photodetector.