Experimental Study on the Frequency Dependence of the Liquid Crystal Infiltrated Photonic Crystal Fibers

The frequency dependence of a nematic liquid crystal infiltrated photonic crystal fiber (LCPCF) subjected to a time varying electric field is studied experimentally in the frequency range from 50 Hz-1 kHz. Due to the millisecond order response times of nematic liquid crystals the transmittance response of the infiltrated fiber is found to be highly dependent on the frequency of the input electric field. The time varying transmission response of the infiltrated fiber is found to vary sinusoidally with a frequency that is twice the frequency of the input electric field. It is demonstrated that the time varying transmission response of the LCPCF can be approximated using an appropriate sinusoidal function. It is shown that a fitted sin(2) function can be used to extract the parameters of the electric field such as frequency and amplitude. The potential application of these structures as all-fiber sensors serving as the core of an electrical signal frequency and amplitude monitoring device is demonstrated and discussed.