Guiding of optical fields in a liquid crystal cylindrical fiber

A cpylindrical nematic liquid-crystal waveguide with an infinite homogeneous isotropic cladding is considered. The dielectric tensor of the liquid-crystal core that governs wave propagation is determined by the configuration of the nematic director. Propagating optical fields can alter the director configuration and thus change the dielectric tensor. We use an iterative numerical scheme to determine the propagation constant as a function of optical power.

Propagation of TM modes in a nonlinear liquid-crystal waveguide.

Electric field-induced mode splitting in a liquid crystal waveguide

In this paper, the design, the realization, and the experimental characterization of an integrated electro-optical switch and a beam deflector, both based on planar nematic liquid crystal (NLC) waveguides, are reported. In order to test such devices, a particular waveguide structure consisting of a three-stage device, having a thin nematic LC film as the middle stage and two glass waveguides as the other stages, has been designed and realized. The electro-optical behavior and the response time have been studied for different configurations for both TE and TM polarized light. By a proper choice of the material parameters and because of the presence of an additional constant bias voltage, we got response time in the microsecond range. The experimental results obtained are very promising in the frame of integrated electro-optical devices, even if the effect underlying the results is not yet understood and probably needs some deeper research into liquid crystal physics and surface interactions.

Fast Integrated Electro-Optical Switch and Beam Deflector Based on Nematic Liquid Crystal Waveguides

We investigated the influence of blue light (λ=450nm) on the optical properties of porous polyethylene terephthalate (PET) films filled with a nematic liquid crystal (E7). In experiments, films of 12μm thickness with randomly distributed open-end pores of well-defined diameters (170, 400, 850nm) were studied. It was found that blue-light illumination of the porous PET films preliminarily treated by an azo dye solution resulted in strong intensity changes when the He–Ne laser beam passed through the sample. The observed effect can be attributed to the heating caused by the absorption of blue light by azo dye molecules.

Optically controlled transmission of porous polyethylene terephthalate films filled with nematic liquid crystal

We consider a cylindrical waveguide consisting of an inhomogeneous anisotropic liquid-crystal core embedded in an infinite homogeneous isotropic cladding. The wave equations for the pure modes are uncoupled but may have complex coefficients owing to the inhomogeneity and anisotropy of the liquid crystal. A simple numerical method is proposed for solving these equations. For the configuration considered, numerical results for the TE modes agree exactly with the analytical solution. For the TM modes, no analytical solution is available, and the unusual result obtained is that the phase of the fields inside the core depends on the distance from the cylinder axis.

H. Lin

Papers

TE and TM modes in a cylindrical liquid-crystal waveguide.

Propagation of TM modes in a nonlinear liquid-crystal waveguide.