Analyses of surface relief gratings inscription in epoxy-azo linear and crosslinked polymers

Abstract

This work evaluates the inscription of surface relief gratings (SRG) in a series of epoxy-azo prepolymers and networks, both based on the same azo chromophore. Variables such as matrix structure (thermoplastic/thermoset), film thickness, exposure time, power of the incident laser beam, and content of azobenzene were analyzed on the final modulation depth of the gratings. The main goal of the article is to achieve the efficient formation of SRGs on crosslinked azopolymer films in a single step, in a reasonable time, and to a significant extent. The progressive erasure of the obtained structures with increasing temperature showed that part of the photoinduced information remained encoded in the material: as the relief partially relaxed above the glass transition temperature of the bulk material (116 °C) and up to 200 °C, its modulation remained in about one third of the initial height, and did not completely disappear.