Wide tuning of SiN microring resonators by auto-realigning nematic liquid crystal

We present wide electrical tuning of microring resonators with auto-realigned nematic liquid crystal (NLC) cladding. By applying electric field, homeotropically-aligned negative Δε NLC with non-rubbed alignment layers is auto-realigned along the microring waveguide due to the protruding of the ridge structure. The consistent cladding index distribution along the microring waveguide produces effective tuning of the resonant wavelength. It achieves a large tuning range of 13nm for TM mode and 2.1nm for TE mode. The NLC reorientation characteristics are investigated by minimizing Oseen-Frank energy. The proposed microring resonator owns the features of large tuning range and bi-polarization wavelength tuning.