Abstract
In this work a waveguide-integrated 2×2 switch operating at the infrared communication wavelength of 1550nm is proposed and theoretically discussed. The device is based 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 4μm-wide and 3μm-thick single-mode rib waveguide. The substrate is a silicon-on-insulator (SOI) wafer with an oxide thickness of 500nm. We calculated an output crosstalk always better than 24dB and insertion losses as low as 3.5dB.
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