Calculation of fully anisotropic liquid crystal waveguide modes

The accurate analysis of optical waveguides is an important issue when designing devices for optical communication. Waveguides combined with liquid crystals have great potential because they allow waveguide tuning over a wide range using low voltages. In this paper, we present calculations that combine an advanced algorithm for calculating liquid crystal behavior and a finite-element mode solver that is able to incorporate the full anisotropy of the materials. Calculation examples demonstrate the validity of our program

A finite element beam propagation method for simulation of liquid crystal devices

An efficient full-vectorial finite element beam propagation method is presented that uses higher order vector elements to calculate the wide angle propagation of an optical field through inhomogeneous, anisotropic optical materials such as liquid crystals. The full dielectric permittivity tensor is considered in solving Maxwell's equations. The wide applicability of the method is illustrated with different examples: the propagation of a laser beam in a uniaxial medium, the tunability of a directional coupler based on liquid crystals and the near-field diffraction of a plane wave in a structure containing micrometer scale variations in the transverse refractive index, similar to the pixels of a spatial light modulator. (C) 2009 Optical Society of Americ

Optical behavior and switching of vertically aligned nematic liquid crystals

In this work, the electro-optical behavior of liquid crystal devices is studied both theoretically and experimentally. In particular, attention has been devoted to the study of vertically aligned (VA) devices as they are one of the most attractive technologies for display applications because of their excellent contrast ratio. The hydrodynamic behavior of VA devices has been studied in this work by means of experiments and simulations. The material influence on the occurrence of reverse flow has been illustrated. It is shown that the threshold voltage for the onset of backflow is a material characteristic. Modeling the electro-optical behavior of liquid crystal devices with micrometer-scale variations involves two aspects. The first step is to determine the orientation of the liquid crystal for the considered geometry in e.g. the presence of an electric field (in the static or dynamic case). The second challenge is to calculate the light propagation through the structure once the director profile of the liquid crystal is known. For this purpose, a finite element beam propagation method (BPM) for the optical analysis of liquid crystal devices has been developed which is fully compatible with the existing liquid crystal modeling software developed at University College London. The finite element tools have been applied to model the electro-optical behavior of liquid crystal (micro)displays and tunable photonic components based on liquid crystals such as waveguides and couplers