We have demonstrated a planar waveguide-based tunable integrated optical filter in indium phosphide (InP) with on-chip micro-electro-mechanical (MEMS) actuation. An air-gap Fabry-Perot resonant microcavity is formed between two waveguides, whose facets have monolithically integrated high-reflectivity multilayer InP/air Distributed Bragg Reflector (DBR) mirrors. A suspended beam electrostatic microactuator attached to one of the DBR mirrors modulates the microcavity length, resulting in a tunable filter. The DBR mirrors provide a broad high-reflectivity spectrum, within which the transmission wavelength can be tuned. The in-plane configuration of the filter enables easy integration with other active and passive waveguide-based optoelectronic devices on a chip and simplifies fiber alignment. Experimental results from the first generation of tunable optical filters are presented. The microfabricated filter exhibited a resonant wavelength shift of 12nm (1513-1525nm) at a low operating voltage of 7V. A full-width-half-maximum (FWHM) of 33 nm was experimentally observed, and the quality factor was calculated to be 46. Several improvements of the MEMS actuator, waveguide, and optical cavity design for the future devices are discussed.
The presentation gives an overview of the ongoing Army Research Laboratory (ARL)/University of Maryland research effort on vertical-cavity-surface-emitting-laser (VCSEL) interconnects and OE processing and why this technology is of interest. ARL is conducting a research and development effort to develop VCSELs, VCSEL arrays, and their hybridization with complimentary metal-oxide-semiconductor (CMOS) electronics and microwave monolithic integrated circuits (MMICs). ARL is also very active in the design, modeling, and development of diffractive optical elements (DOEs). VCSEL-CMOS flip-chip optoelectronic circuits and DOEs are of interest together with detector-CMOS flip-chip circuits to provide digital and analog optoelectronic interconnects in optoelectronic processing architectures. Such optoelectronic architectures show promise of relieving some of the information flow bottlenecks that are emerging in conventional digital electronic processing as the electronic state of the art advances at a rapid pace and the electronic interconnects become a significant limitation. Such optoelectronic interconnects are also of interest in the development of analog optoelectronic processing architectures that are very difficult to implement in conventional electronic circuitry due to the incorporation of dense arrays of interconnects between electronic elements. VCSEL-MMIC- detector flip-chip circuits are of interest for the incorporation of optoelectronic interconnects into analog RF systems where the optoelectronic interconnect offers advantages of size, weight, bandwidth, and power consumption. VCSEL-MMIC interconnects may also play a role in future high- speed digital optoelectronic processing.