Electric Field Sensor Based on Photonic Crystal Cavity With Liquid Crystal

A miniaturized and high-sensitive electric field sensor based on liquid crystal (LC) infiltrated photonic crystal (PC) cavity is proposed, by combining the excellent resonant properties of PC cavity with the good demodulation properties of Mach-Zehnder interferometer (MZI). When external electric field is applied, the refractive index of LC will alter due to the electro-optic effect, and thus the corresponding resonant wavelength of PC cavity will also change. The wavelength shift of the transmitted light of PC cavity can be monitored by detecting the output intensity of MZI, and then enables the detection of the external electric field. With using finite difference time domain (FDTD) method, the wavelength sensitivity of the PC cavity is analyzed and optimized, and then the linear relationship between the output intensity of MZI and the external electric field is calculated. Results demonstrate that a quasilinear measurement of electric field can be achieved with high sensitivity of 7 n W per V/m and detection limit of 0.143 V/m.