Coherent light generators – Particular active media – Semiconductor
Patent
1997-09-22
1999-09-07
Davie, James W.
Coherent light generators
Particular active media
Semiconductor
H01S 319
Patent
active
059498072
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a semiconductor laser device capable of high output operation at high efficiency, which is preferably utilized for communication, laser printers, laser medical treatment, and laser machining and so on.
BACKGROUND ART
For the purpose of increasing in output of a semiconductor laser device, a type of semiconductor laser device has been proposed in which the degree of freedom in the energy band gaps of clad layers formed on the outer sides of carrier blocking layers is increased by providing the carrier blocking layers having a wide band gap and a small thickness on both sides of an active layer. In such a construction, the carrier blocking layers efficiently confine injected carriers into the active layer and since the carrier blocking layers are formed thin, light generated in the active layer can easily pass therethrough and leak out to the outer clad layers. This prevents instantaneous optical damage which is caused by intensive concentration of laser beam at the output end facets of the semiconductor laser device, and increases the COD (Catastrophic Optical Damage) level on the output end facets hence permitting a higher laser output.
FIG. 11(a) is a cross sectional view of such a semiconductor laser device, FIG. 11(b) is a profile of band gaps in their respective layers, and FIG. 11(c) is a profile of the effective index of refraction in case where the carrier blocking layers and the active layer are formed adequately thin so as to hardly affect the waveguide mode. The construction shown in FIG. 11 is called perfect SCH (PCT International Publication No. WO093/16513) in comparison with a known separate confinement heterostructure (SCH).
Referring to FIG. 11(a), formed on an n-GaAs semiconductor substrate (not shown) are, sequentially from lower, a second n-type clad layer (n-AlGaAs) 1, a first n-type clad layer (n-AlGaAs) 2, an n-type carrier blocking layer (n-AlGaAs) 3, an active layer (a GaAs/AlGaAs multi-quantum well layer) 4, a p-type carrier blocking layer (p-AlGaAs) 5, a first p-type clad layer (p-AlGaAs) 6, and a second p-type clad layer (p-AlGaAs) 7.
As shown in FIG. 11(b), the band gap in each of the carrier blocking layers 3 and 5 is greater in width than that in any of the active layer 4 and the clad layers 1, 2, 6, and 7, thus allowing injected carriers to be effectively confined in the active layer 4. Accordingly, the number of carriers which stimulates the laser oscillation will be increased hence improving the efficiency of laser oscillation.
When the carrier blocking layers and the active layer are thin enough to hardly affect the waveguide mode, an effective distribution of refractive index, as shown in FIG. 11(c), is of a slab waveguide structure in which the first n-type clad layer 2 to the first p-type clad layer 6 constitute a portion of high refractive index and each of the second n-type clad layer 1 and the second p-type clad layer 7 constitute portions of low refractive index. Accordingly, light generated in the active layer 4 propagates throughout the high refractive index portion, and as a consequence the peak intensity in the waveguide mode becomes low and hence an optical damage on the output end facets hardly occurs, whereby a high output semiconductor laser device can be realized.
In addition, there is reported an InGaAsP/InP semiconductor laser device of MQW-DCH (multi-quantum well-decoupled confinement heterostructure) provided with hole barrier layers (IEEE, Journal of Quantum Electronics, vol.29, No.6, June 1993, pp. 1596-1600).
In order to obtain a semiconductor laser device of high-output and high-efficiency, it is important to reduce the internal loss due to absorption of free carriers as well as to efficiently confine the injected carriers in the active layer.
In a perfect SCH semiconductor laser device, the injected carriers are successfully confined in the active layer by the carrier blocking layers which has a widest band gap among the layers and is adjacent to the active layer. Since this carrier blocking laye
REFERENCES:
patent: 5737350 (1998-04-01), Motoda et al.
patent: 5811839 (1998-09-01), Shimoyama et al.
Shubert, E. F. "Delta doping of III-V compound semiconductors: Fundamentals and device applications." Journal of Vacuum Science Technology A, vol. 8, No. 3, (May/Jun. 1990), pp. 2980-2996.
Kozen, Atsuo et al. "Metalorganic-vapor-phase-epitaxial growth of Mg-doped Ga.sub.1-x Al.sub.x As layers and their properties." Journal Applied Physics, vol. 59, No. 4, (Feb. 15, 1986), pp. 1156-1158 5(1)--(4).
Hausser, S. et al."1.3.mu.m Multiquantum Well Decoupled Confinement Heterostructure (MQW-DCH) Laser Diodes." IEEE Journal of Quantum Electronics, vol. 29, No. 6, (Jun. 1993), pp. 1596-1600.
Guido, L. et al. "Carbon-doped Al.sub.x Ga.sub.1-x As-GaAs quantum well lasers." Applied Physics Letter, vol. 52 No. 7, (Feb. 15, 1988), pp. 522-524.
Patent Abstracts of Japan--JP 6 013334--Jan. 21, 1994.
"Quantum Well Lasers with Carbon Doped Cladding Layers Grown by Solid Source Molecular Beam Epitaxy" M. Micovic, et al., Applied Physics Letters, vol. 64, No. 4, Jan. 24, 1994, pp. 411-413.
"Spectral Linewidth and Linewidth Enhancement Factor in 1.5 UM Modulation-Doped Strained MQW Lasers" H. Mawatari, et al. International Conference on Solid State Devices and Materials, Aug. 29, 1993, pp. 1041-1043.
"Modulation-Doped Multi-Quantum Well (MD-MQW) Lasers II. Experiment" K. Uomi, et al. Japanese Journal. of Applied Physics, vol. 29, No. 1, Part 01, Jan. 1, 1990, pp. 88-94.
Patent Abstracts of Japan--JP 4 206886 dated Jul. 28, 1992.
Patent Abstracts of Japan--JP 1 214083 dated Aug. 28, 1989.
Fujimoto Tsuyoshi
Naito Yumi
Davie James W.
Mitsui Chemicals Inc.
LandOfFree
Semiconductor laser device 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, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Semiconductor laser device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1811691