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.