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
Liquid Crystals have many applications in photonics, but often the geometrical properties of the photonic structures give problems for controlling the alignment of the liquid crystal. We demonstrate the effect on the orientation of a nematic liquid crystal by structures etched in Silicon-on-Insulator (SOI) wafers, produced by photolithography. We characterize the alignment effect of several patterns, including configurations that allow multiple stable director orientations. Also, the influence of a surface treatment (like deposition of a monolayer on the structured surface) is discussed.