Wavelength-selective devices using silicon-on-insulator

Abstract

This invention describes how commercial silicon-on-insulator material can be used to fabricate both wavelength filters and wavelength-selective photodetectors. The silicon-on-insulator substrates have a buried silicon dioxide layer and a thin top silicon layer and are manufactured for high speed electonics applications. However, in this invention, the thin silicon layer is used as the core of a waveguide and the buried silicon dioxide as a lower cladding region. Another cladding layer and a low index waveguide is fabricated on the commercial substrate to form an asymmetric waveguide coupler structure. The added low index waveguide and the original thin silicon layer form the two waveguides of the coupler. Since the the two waveguide materials have very different indices of refraction, they are only phase-matched at one wavelength. Thus for a given thickness of materials, only one wavelength couples between the two waveguides. By adding an absorptive layer in the silicon waveguide and electrical contacts, wavelength sensitive photodetection is obtained. The buried insulator layer is the key to device operation, providing a very low index buried cladding region.