Ferroelectric and antiferroelectric liquid crystals for optical phase modulation

摘要

A novel liquid crystalline meterial for optical phase modulation is proposed. The material consists of banana shaped dimer molecules, which form a lamellar phase, e.g. a smectic phase. A helical superstructure is induced by means of chiral fragments included in the moolecular structure. Due to polyphilic segregation of hydrogenated and fluorinated molecule segments a cancellation of transversal dipole moments can be avoided and a net polarization of single layers will be obtained. The polarized layers may form ferroelectric or antiferroelectric structures. Application of an electric field in high propagation direction will deform the helix until total unwinding whout recorienting the optical axes of the material, but changing the refractive index for one polarization direction. An estimation of the refractive indices of the material, its index modulation capability and the behavior under e lectric field is presented in this paper. The possible application of the material in phase modulators is discussed.