Double heterostructure semiconductor laser with periodic structure formed in guide layer

Claim 1

A double heterostructure semiconductor laser device comprising: a composite structure including a semiconductor substrate of one conductivity type and a first semiconductor layer disposed on said semiconductor substrate, said composite structure having a first level and a second level, said second level being higher than said first level by a distance equal to or greater than the thickness of said first semiconductor layer, the transition between said first and second levels being in the propagation direction of the laser radiation and having a slant crystal face, and said first semiconductor layer on said second level, having a periodic structure of a prescribed pitch and thickness formed in the propagation direction of the laser radiation, for providing an optical reflector; a second semiconductor layer of said one conductivity type, formed on said first and second levels, having a greater bandgap than that of said first semiconductor layer, said second semiconductor layer comprising two portions the first portion overlying said first level, the second portion overlying said second level; a semiconductor active layer, formed on said second semiconductor layer, having a smaller bandgap than that of said second semiconductor layer, the ends of said semiconductor active layer and first semiconductor layer abutting together in the extension of said slant crystal face; a third semiconductor layer of the opposite conductivity type to that of said substrate, formed on said semiconductor active layer and said slant crystal face, and having a greater bandgap than that of said semiconductor active layer; and a pair of electrodes in contact with said laser device for injecting a current into said semiconductor active layer to produce stimulated emission of radiation.