JP2655429B2 - Semiconductor laser device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to noise reduction of an array semiconductor laser used as a light source of an optical head of an optical disk device for high-speed data transfer.

[Conventional technology]

In order to converge the light emitted from the semiconductor laser element on the information recording medium surface and to perform the information reproducing operation stably and reliably in the optical disk device for recording and reproducing the information,
It is necessary to suppress return light noise generated by reflected light of a semiconductor laser as a light source from an optical disk medium. Therefore, the high frequency current (500MHz
(1 GHz) is superimposed to reduce the coherence of the semiconductor laser, thereby suppressing return optical noise and preventing a decrease in S / N during reproduction. ).

On the other hand, in order to improve the data transfer speed of an optical disk device, a multi-beam optical head device that simultaneously traces a plurality of tracks on an optical disk with a plurality of light beams and records or reproduces information on a plurality of tracks in parallel is known. ing. At this time, using an array semiconductor laser having a plurality of light emitting points in the same package as a light source of the optical head is advantageous in terms of reduction in the number of components of the optical head, miniaturization, and weight reduction.

[Problems to be solved by the invention]

In the above-described multi-beam optical head apparatus, in order to suppress return light noise from the optical disk medium, as shown in FIG. Need to be provided with DC current sources 21 and 22, high-frequency oscillators 31 and 32, and high-frequency current sources 41 and 42. If the oscillating frequencies of the high-frequency oscillators 31 and 32 are different at that time, they interfere with each other, and a signal (beat) having the sum and difference frequencies is generated, and sneak into the detection system of the information recorded on the information recording medium. In particular, when the oscillation frequency of the high-frequency superimposing circuit is close to about 1 MHz to 10 MHz, the beat signal is generated in the vicinity of the information signal band, greatly affecting the reproduced information signal, and making it impossible to reproduce the signal correctly.

SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor laser device which solves such a problem and makes it possible to realize a multi-beam optical head device capable of correctly detecting information recorded on an information recording medium.

[Means for solving the problem]

The present invention provides a semiconductor laser having a plurality of light-emitting points that can be driven independently, a plurality of DC current sources for supplying a DC current to each light-emitting point of the semiconductor laser, and a high-frequency current for each of the DC currents. In a semiconductor laser device including a plurality of high-frequency current sources for superimposition, the plurality of high-frequency current sources have a common high-frequency signal oscillation source.

[Action]

In the present invention, light emitted from a plurality of light-emitting points is superposed at a high frequency by the same frequency from a common high-frequency oscillation source, and does not interfere therewith. Therefore, return light noise can be suppressed at all light emitting points without increasing beat noise due to the high frequency superimposing circuit.

〔Example〕

FIG. 1 shows an embodiment of the present invention. This semiconductor laser device has a laser element that is two light emitting points that can be driven independently.
The array semiconductor laser 1 having the laser elements 11 and 12;
Two DC current sources 21 and 22 for supplying DC current to
And two high-frequency current sources 41 and 42 for superimposing high-frequency currents on the DC currents from the DC current sources 21 and 22, respectively, and one high-frequency oscillator 3 common to the high-frequency current sources 41 and 42.
It is composed of

As described above, in the present embodiment, each of the laser elements 11 and 12 of the array semiconductor laser 1 having two independently drivable light emitting points is driven at the oscillation frequency of the DC current sources 21 and 22 and the high-frequency oscillator 3. High-frequency current sources 41 and 42 are provided.

Therefore, according to the present embodiment, the laser elements 11, 12
Are both modulated at a high frequency at the oscillation frequency determined by the high-frequency oscillator 3, so that they do not interfere with each other.

In the embodiment described above, the number of light emitting points of the array semiconductor laser is two, but the number may be any number as long as it is two or more.

〔The invention's effect〕

As described above, according to the present invention, a multi-beam optical head capable of correctly detecting information recorded on an information recording medium without being affected by a beat signal corresponding to a frequency difference between a plurality of high-frequency current sources The device can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of one embodiment of the present invention, and FIG. 2 is a diagram showing a configuration of a conventional semiconductor laser device. 1. Array semiconductor lasers 11, 12 Laser elements 21, 22 DC current source 3, 31, 32 High frequency oscillator 41, 42 High frequency current source

Claims (1)

(57) [Claims] 1. A semiconductor laser having a plurality of light-emitting points that can be driven independently, a plurality of DC current sources for supplying a DC current to each light-emitting point of the semiconductor laser, and a high-frequency current supplied to each of the DC currents. A semiconductor laser device comprising a plurality of high-frequency current sources for superposing the same, wherein the plurality of high-frequency current sources share a high-frequency signal oscillation source.