Coherent light generators – Particular active media – Semiconductor
Patent
1994-02-22
1995-07-04
Davie, James W.
Coherent light generators
Particular active media
Semiconductor
372 92, 372108, 437129, H01S 319
Patent
active
054307511
ABSTRACT:
The invention relates to a semiconductor diode laser whose strip-shaped active region is limited by an end face which is curved for forming a lens of a given strength. A disadvantage of the known diode is that it has a comparatively high starting current. This is found to be caused inter alia by the etching necessary for forming a curved end face. During etching, unevennesses arise in the curved end face where scattering of the generated radiation occurs. This increases the starting current of the diode. A diode according to the invention is characterized in that the curved end face is covered with a covering layer of a material having a refractive index different from that of the active layer, and the refractive index of the covering layer and the curvature of the end face are so chosen that the scattering of the generated radiation is a minimum for the given strength of the lens. The scattering is a minimum through a choice of the smallest possible difference in refractive index between the covering layer and the active layer, preferably below 0.5. Preferably, the radius of curvature of the end face is smaller than 2.5 .mu.m. The covering layer preferably comprises a semiconductor material, for example, the same material as a cladding layer. In diode lasers with a lateral cladding layer, the latter layer and the covering layer may be provided in a single deposition step, which is very favourable. The invention, accordingly, also relates to a method of manufacturing diode lasers according to the invention.
REFERENCES:
patent: 4935939 (1990-06-01), Liau et al.
Biren Steven R.
Davie James W.
U.S. Philips Corporation
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