Patent ID: 6181721
Filing Date: 2001-01-30
Classification: B82Y,H01S

Abstract:
A semiconductor laser having a visible red spectrum output comprising:a broadened gain section forming at least one portion of said laser;a narrow single mode section forming at least one other portion of said laser and optically coupled at one end to a narrow end of said broadened gain section;the ratio of the pumped areas of the broadened gain section compared to the narrow single mode section being large so that the broadened gain section acts as a high gain region and the narrow single mode section has a given limited carrier density;the broadened gain section and narrow single mode section forming, at least in part, an optical cavity for propagation of light wherein the light expands into said broadened gain section through the broadened gain section narrow end from said single mode section to a reflector at an other end of said broadened gain section;a small portion of ligh being reflected back from said other end reflector into the narrow single mode section due to its narrow width;at least said single narrow single mode section including a semiconductor substrate and a semiconductor cap layer between which is formed a plurality of a semiconductor confinement layers amd a semiconductor active region for said laser, the bandgap differences between said substrate and said cap layer and said cladding layers comprising a large band offset providing a barrier to the flow of carriers to the active region;the improvement comprising:refractive index graded layers formed between either said substrate or said cap layer and said cladding layers or both in said narrow single mode section, said index graded layers having monotonically distributed bandgap profile to improve carrier flow to achieve higher carrier density than said given carrier density in said narrow single mode section section and , correspondingly, the higher levels of optical gain achieved in the broadened gain section increasing the overall power output capability from the laser.