Surface relief gratings induced by a nanosecond pulse in a liquid-crystalline azo-polymethacrylate

Abstract

Surface relief gratings have been generated in an azobenzene side chain liquid-crystal polymer using an intensity interference pattern from two coherent laser pulses (532nm and 4ns). We elucidate whether peaks or trenches correspond to the high intensity regions of the interference pattern. For low-energy pulses, peaks are generated in the irradiated areas while trenches appear for energies above a threshold (around 100mJ∕cm2 per beam). This phenomenology, together with the lack of relief when polarization patterns are used, indicates that in this polymer surface relief has a thermal origin.