Highly diffractive, reversibly fast responsive gratings formulated through holography

Abstract

Versatile and reversibly rapid responsive one-dimensional photonic crystals with a diffraction efficiency of 97%, which consisted of uniformly 273 ± 48 nm wide liquid crystal belts within transmission holographic polymer dispersed liquid crystal (HPDLC) gratings, were formulated by a facile single step holography based on a hyperbranched monomer. The effect of the monomer average functionality on the photopolymerization kinetics and the electro-optical performances as well as the grating morphologies was investigated. The results show that the low intrinsic viscosity of the hyperbranched monomer accounts for a well-structured morphology in terms of providing a prolonged gelation time for the liquid crystals to diffuse from the light illumination region during the holographic polymerization induced phase separation. Another intriguing observation is that with an increase in the hyperbranched monomer loading, the diffraction efficiency of the HPDLC gratings gradually increases from zero to an average of 94% and then levels off. This is quite different from previous results that gave less than a 50% diffraction efficiency when the monomer average functionality was larger than 4.