Future optical interconnect architectures with vertical and lateral paths will need to be silicon-based for integration of waveguides, modulators, and detectors with microelectronics. Current research efforts concentrate on operation beyond the band-edge wavelength of 1.12 um, where silicon is nominally transparent. Potential integration of optoelectronic devices at wafer level may lead to the development of optical interconnection technologies based on infrared light sources at 1.3um. Recent research in this area indicates that a refractive index change as large as 0.01 can be achieved in silicon even though silicon does not exhibit a linear electrooptic effect. This electrically induced refractive index change is based on the free-carrier effect, (e.g., in a p-n junction) and can be used for light modulation. Physical Optics Corporation proposes to use its holographic recording of photoresist gratings to develop an optical modulator based on a waveguide grating coupler. The coupling efficiency can be modulated by very small changes of refractive index in the structure because of the narrow acceptance angle of the guided mode. Full modulation depth of the guided wave can be achieved with current densities under 10 uA/um2. This structure can be also used for spatial light modulators.
