Photorefractive Binary System Based on Ferroelectric Liquid Crystals

Abstract

In this paper, results of studies regarding the photorefractive effect in bistable surface stabilized ferroelectric liquid crystals are reported. In particular, an innovative approach toward the optical control of polarization switching in C 70 -doped bistable devices by means of a photogenerated space-charge field is described. The photorefractive nature of the resulting refractive index gratings is confirmed by two-beam coupling and direct phase shift measurements. The influence of an applied field and of light intensity on grating formation is also studied. The photorefractive gratings obtained by using this approach are stable, easily erasable, and rewritable. The described devices are "binary" systems, in which the refractive index switches only between two possible values. Bistable systems constitute a completely new class of photorefractive materials, with peculiar properties which distinguish them from previously developed media.

Light-activated modulation and coupling in integrated polymer–liquid crystal systems

“…However, it is not essential to use bulk photorefractive materials to achieve a strong refractive index modulation. More recently, efficient beam coupling was shown in a wide range of materials and devices, including LC light valves based on organic [4,8] and inorganic [2] photoconductors, polymer-dispersed [9] and ferroelectric LCs [10], and photorefractive polymers [11,12].…”