FABRICATION OF GRATINGS FOR INTEGRATED OPTOELECTRONICS

High quality surface gratings for outcoupling and feedback in InGaAs/A lGaAs semiconductor lasers were fabricated using direct electron-beam writing and chemically assisted ion beam etching. An epitaxially incor porated etch-stop layer in combination with selective chemical etching was used for precise positioning of the grating with respect to the w aveguide. Surface normal outcoupling efficiency exceeding 60% was achi eved for rectangular gratings with equal width, height, and space of t he grating teeth. For blazed gratings, a strong dependence of both ref lectivity and up/down coupling ratio on the grating orientation was fo und.