Radially realigning nematic liquid crystal for efficient tuning of microring resonators

The efficient tuning of microring resonator with the radially realigning nematic liquid crystal (NLC) cladding is presented. By applying the voltage on the in-plane annular electrodes, the produced electric field realigns the homeotropically-aligned NLC in the radial direction. Under the voltage sufficient for 90° NLC reorientation, the guided mode senses the consistent cladding index distribution along the microring waveguide with the maximal index change equal to the optical anisotropy of NLC. The resultant tuning of the resonant wavelength has a blue shift of 23.1nm for the TM mode and a red shift of 10.1nm for the TE mode. The tuning rates for the TM and TE modes are -1.95nm/V and 0.90nm/V. The proposed microring resonator owns the excellent features of wide tuning ranges and high tuning rates for the TM and TE modes.