Dual-Period Polarization-Dependent Diffraction Gratings Based on a Polymer-Stabilized Liquid Crystal.

In this paper, we demonstrate the first ever dual-period diffraction gratings that do not require electrical tuning to obtain the effect of period change. Our method allows for multiplication of the base period by proper modification of the subsequent slits of the grating. The proposed elements are fabricated by selective photopolymerization of a composite based on a nematic liquid crystal. The gratings are formed by polymer stabilization of a liquid crystal in different orientations of the molecules in selected grating slits to allow for period manipulation. The operating principle is based on changing the phase delay introduced by the slits depending on polarization direction of incident light with respect to the director in each type of slit, which allows to change the grating's period. The proposed technique was successfully utilized to obtain diffraction gratings with either doubling or tripling of the period.

Photopolymerization of 1D photonic structures induced by nematic-isotropic phase transition in liquid crystal.

In this paper, two types of polymer-stabilized periodic structures created by photopolymerization of a nematic liquid crystal confined in a cylindrical structure are presented. Both types of structures were induced by nematic-isotropic phase transition in liquid crystal doped with gold nanoparticles. The first type of structure was created by stabilizing periodic phase separation at the nematic-isotropic phase transition temperature. As a result, a periodic structure with two distinct molecular orientations of nematic liquid crystal was achieved. The period of this structure was equal to the period induced by nematic-isotropic phase separation. The second type of structure, also related to the phase transition, was created due to an induced periodic density change of gold nanoparticles in the sample volume. Through photopolymerization it was possible to preclude the dispersion of gold nanoparticles while preserving the periodicity. An increased concentration of gold nanoparticles caused periodic defects in molecular orientation of the liquid crystal. Both types of structures were stable at room temperature. Consequently, two types of 1D photonic structures stabilized by photopolymerization are presented.