1.55 μm silicon-based reflection-type waveguide-integrated thermo-optic 2 x 2 switch

In this work a waveguide-integrated 2 x 2 switch operating at the infrared communication wavelength of 1550 nm is proposed and theoretically discussed. The device is bared on the total internal reflection (TIR) phenomenon and the thermo-optic effect (TOE) in hydrogenated amorphous silicon (a-Si: H) and crystalline silicon (c-Si). It takes advantage of a bandgap-engineered a-Si: H layer to explore the properties of an optical interface between materials showing similar refractive indexes but different thermo-optic coefficients. In particular, thanks to modern plasma-enhanced chemical vapour deposition (PECVD) techniques, the refractive index of the amorphous film can be properly tailored to match that of c-Si at a given temperature. TIR may be therefore achieved at the interface by acting on the temperature. The device is integrated in a 4 mu m-wide and 3 mu m-thick single-mode rib waveguide. The substrate is a silicon-on-insulator (SOI) wafer with an oxide thickness of 500 nm. We calculated an output crosstalk always better than 24 dB and insertion losses as low as 3.5 dB. (C) 2011 Elsevier GmbH. All rights reserved.