High speed thermo-optic phase shifter and devices comprising same

1 12 212212In accordance with the invention, a high speed thermo-optic phase shifter comprises a length of optical waveguide including a waveguiding core of a first material having an index of refraction nand a first order temperature dependence |dn/dT| and, optically coupled to the core, a length of a second material having an index npreferably greater than the core (n>n) and a first order temperature dependence |dn/dT| than the core (|dn/dT|>|dn/dT|). Advantageously, the length of second material is adiabatically tapered at both ends. Upon heating, as by a resistance heater, the second material changes the optical pathlength by an amount predominantly determined by |dn/dT| providing faster switching speed. In a preferred embodiment, the core comprises silica, and the second material comprises silicon to produce switching speeds up to a few hundred MHz.