In-Line Polarization Controller Based on Liquid-Crystal Photonic Crystal Fibers

Compact polarization control elements based on index-guiding soft-glass photonic crystal fibers infiltrated with nematic liquid crystals are proposed and thoroughly studied. The nematic director profiles at the fiber´s cross section are consistently calculated by solving the coupled electrostatic and elastic problem, in the context of an analysis on the tunability of liquid-crystal-infiltrated photonic crystal fibers. The fiber´s dispersive properties and light propagation in the proposed polarization controller are studied by means of a fully anisotropic finite-element-based beam propagation method. The electrically induced evolution of the state of polarization is mapped on the Poincaré sphere. Efficient polarization conversion is demonstrated, with a crosstalk of -50 dB, for a total device length of 4.65 mm and a maximum applied voltage of 150 V. Crosstalk values lower than -20 dB are achieved over a 30 nm window. The proposed devices are envisaged as compact all-in-fiber dynamic polarization controllers.