Continuously tunable all-in-fiber devices based on thermal and electrical control of negative dielectric anisotropy liquid crystal photonic bandgap fibers

We infiltrate photonic crystal fibers with a negative dielectric anisotropy liquid crystal. A $396\mathrm{nm}$ bandgap shift is obtained in the temperature range of $22–80°\mathrm{C}$, and a $67\mathrm{nm}$ shift of long-wavelength bandgap edge is achieved by applying a voltage of $200\mathrm{Vrms}$. The polarization sensitivity and corresponding activation loss are measured using polarized light and a full broadband polarization control setup. The electrically induced phase shift on the Poincaré sphere and corresponding birefringence change are also measured. According to the results, tunable wave plates working in the wavelength range of $1520–1580\mathrm{nm}$ and a potential for realizing a polarimeter working at the $1310\mathrm{nm}$ region are experimentally demonstrated.