A new device structure, a collinear asymmetrical directional coupler using In2O3/InxSn1-xOy heterostructure thin film, is introduced which will decrease the power consumption needed to obtain full intensity modulation, is adaptable to any substrate, has a high multiplexing capability, and will potentially give yield to a new line of both electro-optic and all-optic devices. Conventional coplanar directional couplers must have waveguides of exactly equal widths which is extremely difficult to achieve. We will eliminate the stringent waveguide channel tolerance requirements through a variable guided mode effective index technique. Unlike the III-V and II-VI compound semiconductor heterostructure, the In2O3/InxSn1-xOy film can be grown on any surface. Therefore, an active device can be built on an array of substrate materials. The In2O3/InxSn1-xOy has a transparent bandwidth from 400 nm to mid-infrared. A large number of optical wavelengths can also be multiplexed. Finally, the index modulation of In2O3/InxSn1-xSn1-xOy film is brought about by carrier injection. Consequently, both electro-optic and all optical devices can be realized based on the novel concept. The index modulation with carrier injection is two orders of magnitude higher than with the linear electro-optic effect. The interaction length is expected to be compatible with multi-quantum well devices.
