The optical and dielectric properties of liquid crystals are generally determined by the rigid core of the molecules. The difference in optical tilt angle between the two states is considerably reduced from that in the bookshelf structure, and is typically between one half and one third of that available in the bookshelf structure. A spatial light modulator is an electro-optic device capable of modulating the intensity, phase or polarization of an optical wave front both in space as well as in time. Compared with other optically controlled switching devices, such as multiple quantum well devices or nonlinear effect devices they demonstrate very high parallelism and sensitivity but also a much slower response time. In a sufficiently thin antiferroelectric liquid crystal cell the helical structure is suppressed and the simplest structure which can then form is one where the molecular tilt plane lies parallel to the surface.