New approaches for chip-to-chip interconnects: Integrating porous silicon with MOEMS

We describe two types of active optical devices developed for use as free-space optical interconnects (FSOIs) for chip-to-chip communications. The design of both types of devices-membrane and freestanding structures-includes both optical and mechanical components. The optical component contains porous silicon (PSi) with customized optical properties fabricated by electrochemical etching of silicon. The mechanical part of the devices is composed of metal/nitride bimorph thermal actuators. The membrane devices form concave mirrors when actuated, and can be used to focus the incoming optical signals and correct any optical misalignment within the input/output (I/O) fabric. The freestanding devices have out-of-plane optical components, whose tilting angle is controlled by the current applied to the actuator. These devices can function as either reflectors or tunable optical filters. By incorporating the developed PSi diffractive optical element (DOE) into the freestanding structure, another type of freestanding device is realized for beamsplitting applications. Details of the fabrication, testing, and integration of these PSi-based devices are presented.