Demonstration of a Thermo-optic Phase Shifter by Utilizing High-Q Resonance in High-index-contrast Grating

A thermo-optic phase shifter is proposed and demonstrated by utilizing the high-Q resonance in high-index-contrast grating (HCG). The Q-factor up to ∼12000 is measured in a footprint of 110  μm×300  μm. By heating the HCG with paired metal strip micro-heaters, the optical resonance shifts, which induces phase modulation. A phase shift of ∼1.2π under heating power of ∼32  mW is directly observed and demodulated from the fringes shifting in a Michelson interferometer. The proposed configuration can also be extended to realize high-speed phase shift by adopting electro-optical modulation.