Coherent light generators – Particular active media – Semiconductor
Patent
1996-10-30
2000-06-06
Davie, James W.
Coherent light generators
Particular active media
Semiconductor
372 46, H01S 319
Patent
active
060728175
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a low noise self-sustained pulsation type semiconductor laser device used as a light source for an optical disk system, etc.
BACKGROUND ART
In recent years, semiconductor laser devices (laser diodes) are in increasing demand in the fields such as optical communication, laser printers, and optical disks. Under these circumstances, active research and development have been conducted with respect to various semiconductor laser devices with particular emphasis on those of GaAS type and InP type. In the field of optical information processing, systems for recording and reproducing information by using 780 nm-band AlGaAs type laser diodes as light sources have been put into practical use. Such systems became widespread for use with recording and reproducing compact disks.
However, recently, the increase in storage capacity of these optical disks has come to be strongly demanded. Along with this, it has come to be required to obtain semiconductor laser devices capable of emitting laser light with shorter wavelengths.
AlGaInP type semiconductor laser devices are capable of allowing laser oscillation to be realized at wavelengths of 630 nm to 690 nm in the red region. In the present specification, (Al.sub.x Ga.sub.1-x).sub.0.5 In.sub.0.5 P (O.ltoreq..times.<1) is abbreviated simply as "AlGaInP". At present, of various practical semiconductor laser devices, the AlGaInP type semiconductor laser devices are capable of emitting laser light with the shortest wavelengths, so that they hold great promise as next-generation large capacity light sources for optical information recording, in place of AlGaAs type semiconductor laser devices which have been widely used in the past.
For evaluation of semiconductor laser devices, intensity noise and temperature characteristics are important elements in addition to wavelengths of laser light. In particular, when a semiconductor laser device is used as a light source for reproducing optical disks, small intensity noise is very important. This is because intensity noise induces errors while signals recorded on an optical disk are read. The intensity noise of the semiconductor laser device is caused not only by changes in temperature of the device but also by light partially reflected from the surface of the optical disk to the semiconductor laser device. Thus, semiconductor laser devices, which have small intensity noise even when reflected light is fed back to the devices, are indispensable as light sources for reproducing optical disks.
Conventionally, in the case of using AlGaAs type semiconductor laser devices as low output light sources dedicated for reproducing optical disks, saturable absorbers are intentionally formed on both sides of ridge stripes in the devices so as to reduce noise. The use of such a structure enables a longitudinal mode of laser oscillation to be multiple. When the feedback of laser light to a device, the changes in temperature of the device, etc., are caused while laser oscillation is realized in a single longitudinal mode, a slight change in gain peak allows laser oscillation to start in another longitudinal mode close to the longitudinal mode in which the laser oscillation has already been realized. This causes mode competition between the new longitudinal mode and the original longitudinal mode, resulting in noise. Thus, in the case of multiple longitudinal modes, the changes in intensity of each mode are averaged and the intensity of each mode does not change due to the feedback of laser light to the device, the changes in temperature of the device, etc. This permits stable low noise characteristics to be obtained.
Japanese Laid-Open Patent Publication No. 63-202083 discloses a semiconductor laser device capable of obtaining stable self-sustained pulsation characteristics. According to this publication, a self-sustained pulsation type laser diode is realized by providing a layer capable of absorbing light generated in an active layer.
Furthermore, Japanese Laid-Open Patent Publication No. 6-26
REFERENCES:
patent: 4435809 (1984-03-01), Tsang et al.
patent: 4961197 (1990-10-01), Tanaka et al.
patent: 5003549 (1991-03-01), Mitsui et al.
patent: 5053356 (1991-10-01), Mitsui et al.
patent: 5214663 (1993-05-01), Kakimoto et al.
patent: 5416790 (1995-05-01), Yodoshi et al.
patent: 5506170 (1996-04-01), Yodoshi et al.
patent: 5581570 (1996-12-01), Yoshida et al.
patent: 5751756 (1998-05-01), Takayama et al.
English Translation of JP 6-196810 by Keiichi et al, Jul. 1994.
Office Action for Japanese Patent Application Serial No. 8-529169 dated Sep. 22, 1998.
PCT--International Publication #WO 92/20128, International Publication date Nov. 12, 1992. International Application #PCT/GB92/00826.
International Search Report for Application PCT/JP96/00801; dated Mar. 27, 1996.
Adachi Hideto
Fukuhisa Toshiya
Kamiyama Satoshi
Kidoguchi Isao
Mannoh Masaya
Davie James W.
Matsushita Electric - Industrial Co., Ltd.
LandOfFree
Semiconductor laser device and optical disk apparatus using the does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Semiconductor laser device and optical disk apparatus using the , we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Semiconductor laser device and optical disk apparatus using the will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2220411