Abstract

A multiple quantum-well (MQW) layer was designed to support a single slab mode for both the TE and TM polarizations. Strain-induced waveguides were fabricated by plasma-enhanced vapor-phase deposition and etching of silicon nitride to leave stripes of the film 2000 Å thick and widths ranging from 4 to 10 μm on the surface of the MQW layer. A schematic drawing of the waveguide cross section is shown in Fig. 1. The processed layer was cleaved at the two ends to leave waveguides that were approximately 1 mm long. The narrowest waveguides only allowed for the propagation of the fundamental mode under the center of the stripe, whereas the wider waveguides were found to support two edge modes under the inside edges of the SiN_x film. The two edge modes were strongly coupled through the overlap of their evanescent tails and the structure exhibited directional coupler properties with a critical coupling distance of approximately 1 mm.

© 1990 Optical Society of America