1In-line Polarization Controller Based on Liquid-Crystal Photonic Crystal Fibers

Abstract—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 LC-infiltrated PCFs. 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 Poincare ́ sphere. Efficient polarization conversion is demonstrated, with a crosstalk of −50dB, for a total device length of 4.65mm and a maximum applied voltage of 150V. Crosstalk values lower than −20dB are achieved over a 30nm window. The proposed devices are en-visaged as compact all-in-fiber dynamic polarization controllers. Index Terms—Photonic crystal fibers, nematic liquid crys-tals, highly-birefringent fibers, beam propagation method, polarization-controllers. I