Light-controlled electro-optic response in a ferroelectric liquid crystal with sign reversal of the spontaneous polarization P_S

Abstract

At fixed field polarity, the direction of molecular switching in ferroelectric liquid crystals, and hence the sign of electro-optic response, depends on the sign of P_S. Here, we present a light-controlled electro-optic response of a ferroelectric liquid crystal mixture consisting of a single component feiroelectric host, that exhibits a sign reversal of P_Swith temperature, and a small amount of azo dye. It was found that, due to photoisomerisation of the azo dye, the sign reversal temperature of P_S(T_rev) increased upon UV illumination. As consequence, if the mixture was illuminated at temperature several degrees above T_rev, the electro-optic response reversed its sign. This effect seems to be applicable in light-controlled liquid crystal light switches.

Keywords:

• Ferroelectric liquid crystal
• photo-isomerisation
• sign reversal of P_S
• light-controlled electro-optic response