JPS63199481A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To obtain a semiconductor laser device which is simple and reliable and oscillates laser beams large in coherent length, by focusing output beams which are emitted backward from the semiconductor laser device and next making the beams return to the semiconductor laser device. CONSTITUTION:A means in which back output beams are focused and next made to return is provided. For example, a front of a semiconductor laser device 1 is coated with an Al2O3 dielectric 2 of a reflection factor of 12%, and the rear is coated with an Al2O3 dielectric 3 of a reflection factor of 32%. A glass 4 whose lens part 5 and whose surface opposite to the lens part 5 are coated with reflective films 6 is disposed behind the semiconductor laser device 1. Laser beams emitted backward from the semiconductor laser device 1 are made to pass through the lens part 5 and advance on a route 7 and are condensed on the reflective film 6, and next the beams are reflected on the film 6 and again advance on the route 7 and return to the semiconductor laser device 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a semiconductor laser device, and more particularly to a semiconductor laser device equipped with noise countermeasures when used as a light source for reproducing optical discs and the like.

[Prior Art] When a semiconductor laser is used as a reproducing light source for reproducing optical discs, etc., noise is induced by the return light from the optical disc, etc., and mode competition noise occurs due to fluctuations in operating temperature, which may cause problems in system signal pairing. This results in a reduction in the noise ratio. As a countermeasure to this problem, methods have been adopted to reduce the relative noise intensity by causing the semiconductor laser to undergo continuous relaxation oscillation, or by superimposing a high-frequency current on the drive current to shorten the coherent length of the oscillated laser light. .

[Problems to be Solved by the Invention] The conventional means described above pose the following problems.

If the method of causing continuous relaxation oscillation in the semiconductor laser is adopted, high output (about 30 to 40 mW) cannot be obtained, and a separate high frequency superimposition circuit is required to superimpose the blade high frequency on the oscillating laser, which is expensive and high frequency. The method of shielding was a big problem.

The present invention has been made to solve these problems, and an object of the present invention is to provide a simple and reliable semiconductor laser device that oscillates a laser beam with a long coherent length.

[Means for Solving the Problems] The semiconductor laser device according to the present invention efficiently reflects and focuses the laser light output emitted backward on the backside resonance surface of the semiconductor laser, and then returns it to the semiconductor laser. be.

[Operation] In this invention, laser oscillation occurs only under phase conditions that simultaneously satisfy the resonance condition formed by the semiconductor laser and the resonance condition during feedback of the backward output light, and as a result, laser light with a long coherent length is generated. can oscillate.

[Example] FIG. 1 is a schematic diagram showing an embodiment of the present invention.

In the figure, the front surface of the semiconductor laser 1 has a reflectance of 12%.
coated with fl 20a dielectric, the rear surface has a reflectance of 3
It is coated with 2% Au, O, dielectric 3. Further, behind the semiconductor laser 1, a lens section 5 and a glass 4 having a reflective film 60 attached to the surface facing the lens section 5 are installed.

The present invention will be explained in detail below.

Laser light emitted from the rear of the semiconductor laser 1 passes through the lens section 5 and is focused on the reflective film 6 along a route 7, where it is reflected again and returned to the semiconductor laser 1 along the same route 7. It will be done. In such a configuration, laser oscillation occurs only under a phase condition that simultaneously satisfies both the resonance condition formed by the semiconductor laser 1 and the resonance condition formed by the glass 4 side. However, in order to increase this oscillation effect, that is, the effect of increasing the coherent length of the oscillated laser light, it is necessary to return a sufficient amount of the backward emitted light to the semiconductor laser 1. This is because if the amount of returned light is small, the influence of temperature changes in the semiconductor laser itself or return light from an optical disk or the like will become greater, making it impossible to obtain laser light with a long coherent length.

In one embodiment of the present invention, a lens portion 5 and a reflective film 6 are provided on the glass 4 side in order to ensure this return light, and the rear emitted light is efficiently focused by the lens portion 5 and the reflective film 6. The structure employs a structure that allows the water to return to its original state.

FIGS. 2 and 3 are charts comparing the relative noise intensity of a semiconductor laser device according to an embodiment of the present invention and a conventional semiconductor laser device that does not employ the means of this embodiment.

In Figure 2, the horizontal axis represents the ambient temperature, and the vertical axis represents the relative noise intensity (
RI N) is plotted for the embodiment and the conventional example.

In FIG. 3, the amount of light returned from an optical disk or the like is plotted on the horizontal axis, and the relative noise intensity (RIN) is plotted on the vertical axis.

As a result of both figures, the RIN of the conventional example is 10-13/Hz depending on the ambient temperature or the amount of returned light.
Although there are points where the above is true, in the example, R4N is 10-
It has been shown that the noise is extremely low, ”/Hz.

In addition, in the second embodiment, lenses and mirrors were used as means for converging and returning the rear emitted light, but it goes without saying that other structures can produce similar effects.

[Effects of the Invention] As explained above, this invention focuses the rear laser light output of a semiconductor laser and then returns it, so the coherent length of the oscillated laser light becomes longer, and the front laser output light can be used as reproduction light for optical discs, etc. In this case, it becomes a highly reliable semiconductor laser device that is less susceptible to the effects of returned light and ambient temperature.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram showing an embodiment of the present invention, Fig. 2 is a chart comparing an embodiment of the invention and a conventional example in terms of relative noise intensity with respect to ambient temperature, and Fig. 3 is a diagram showing the relative noise intensity of the embodiment of the invention. 3 is a chart comparing one embodiment and a conventional example in terms of relative noise intensity with respect to the amount of returned light. In the figure, 1 is a semiconductor laser, 4 is glass, 5 is a lens portion, and 6 is a reflective film. Note that the same reference numerals in each figure indicate the same or corresponding parts. Figure 1 Oath Figure 82 ≧ V cause and environment and (°O)

Claims (1)

[Claims] comprising means for focusing and returning the rear optical output;
Semiconductor laser equipment.