Effects of carrier diffusion in the design and measurement of waveguide couplers and etched facets for a semiconductor-integrated optical routing array

Use of electrically variable couplers and etched facet mirrors in a coupled guide cross point switching and routing array is examined. Theoretical analysis, and experimental results of carrier injection into double heterojunction semiconductor rib waveguide electrically variable couplers, together with effect on modal reflectivity at an etched facet mirror, are presented. Results demonstrate that carrier injection is a viable and efficient method for reducing the effective index beneath the guide rib leading to both detuning of a coupled guide structure, and for effectively `destroying' the guiding ability of one guide. The importance of the diffusion contrast on the operational efficiency of such devices is shown to be significant. Etched mirrors prove theoretically to be viable structures for changing the waveguide direction in this material. Reflectivity is shown not to vary with carrier injection for the proposed guides.