WAVEGUIDING EFFECT IN A CELL WITH A LIQUID CRYSTALLINE CORE

Abstract

We present a model for the propagation of an optical field in a nematic planar cell where hydrodynamic flows are neglected. We show that the distortion induced by the field produces an index-gradient which produces a waveguide effect that concentrates the electromagnetic field and its energy density in the central part of the cell. This is shown by first performing a perturbative analysis of the reorientational dynamics and the coupled dynamics of the electromagnetic field in powers of the dielectric anisotropy of the nematic. Up to the first order, we calculate analytically the normal modes of the field, its dispersion relation and the electromagnetic energy density spatial distribution within the cell. The existence of this effect is also shown in a non-perturbative way by calculating the ray trajectories from the eikonal equation for a low intensity beam in the optical limit. We show that the trajectories indeed bend towards the middle part of the cell.