Abstract

The efficient operation of thin-film devices requires that a substantial fraction of the input laser power be coupled through the waveguide and into a useful output beam. When high-quality waveguide structures are used, efficient coupling can be achieved with either a prism or a grating coupler. Work with free-standing (slab) waveguides used in an early model of a thin-film modulator for CO₂ laser radiation (Ref. ¹) has shown both that practical waveguide structures can have serious structural imperfections in the coupling regions and that device constraints may preclude the use of optimized waveguide and coupler designs.

© 1976 Optical Society of America