Wave guiding with liquid crystals

Optical waveguides are widely used in the telecom industry for long distance data transport. Glass fibers are designed to have minimal losses. Different functionalities have been integrated in waveguides, such as wavelength filtering, amplitude modulation and routing. Liquid crystals are promising, because their optical properties can be modified by applying a small voltage or by illumination with light. The variation in optical properties can be exploited in different kinds of waveguide systems. It is possible to generate a wave guide in bulk liquid crystal by modulating the director orientation in an appropriate pattern. Some guided modes in such pure liquid crystals are discussed. Because the liquid crystals are anisotropic, the modes have some unusual properties. The influence of light can lead to director reorientation and modify the waveguiding properties. This optical non-linearity determines largely the light propagation. In hybrid waveguides, liquid crystal are used in combination with a material with higher (in the core) or lower (in the cladding) refractive index. Silicon on insulator waveguides are convenient components to study the tuning possibilities in combination with liquid crystals.