Polymer-stabilized periodic waveguiding structures in liquid crystalline materials

Abstract

The aim of this work is to create the regions of different effective refractive index in typical liquid crystal cell thanks to the polymer-stabilization. For this purpose typical liquid crystalline material, namely E7, has been combined with a small amount of the mixture of RM257 monomer and UV-sensitive activator, with percentage weight less than 10%. Thanks to the photo-polymerization process it is possible to obtain polymer-stabilized molecular orientation inside LC cell. In particular, periodic changes in spatial distribution of effective refractive index in LC layer have been achieved thanks to selective irradiation with UV light. Determination of suitable dose of both the monomer and UV-activator to be added to LC material, as well as of irradiation intensity and time, is essential and highly required to provide repeatable and good-quality periodic waveguiding structures. Eventually, functionality of the liquid crystal cells with distinguished regions of different molecular orientation, and in particular with combination of the planar and homeotropic alignment, has been experimentally tested by launching the near-infrared light beams of orthogonal linear polarizations. Thanks to the molecular reorientation induced by external electric field and/or by electromagnetic wave, it is additionally possible to control character of light propagation by electric bias and optical power, respectively. Proposed polymer-stabilized periodic waveguiding structures in liquid crystalline materials may find potential applications as functional elements and devices for LC-based integrated optics.