1.55-´m reflection-type optical waveguide switch based on thermo-optic effect

Abstract

Based on the total internal reflection (TIR) phenomenon and the thermo-optic effect in hydrogenated amorphous silicon (a-Si:H) and crystalline silicon (c-Si), a symmetric rib optical waveguide integrated switch is proposed and theoretically discussed. The device exploits the similar refractive index coupled to the different thermo-optic coefficient in the two materials. The possibility of alloying and doping for the band-gap engineering of a-Si:H, by means of the gas phase composition during the modern plasma enhanced chemical vapour deposition process, which takes place at temperatures as low as 220 degrees C, makes this semiconductor ideal for this type of application. In particular the refractive index at room temperature of the amorphous film can be properly tailored to match that of c-Si in order to achieve the light switching when the device experiences a given temperature change. TIR may be achieved however at the interface by acting on the temperature, because the two materials have different thermo-optic coefficient. The integrated single-mode rib waveguide is 4 μm wide and 3 μm high. The substrate is a SOI wafer with an oxide thickness of 500 nm. The switch has a quite short operation length of about 280 μm. The device performance is analyzed at the wavelength of 1.55 μm. It shows that the output crosstalk and insertion loss are less than -26.9 dB and 3.5 dB, respectively.