Optimization of an acrylamide-based photopolymer system for holographic inscription of surface patterns with sub-micron resolution

We describe the optimization of the holographic patterning of sub-micrometre surface relief structures in an acrylamide-based photopolymer. A substantial improvement in the photoinduced surface relief resolution was achieved by altering the photopolymer chemical composition and by introducing a single step post-recording thermal treatment of the layers. It was observed that, by optimization of the chemical composition of the photopolymer layers, the maximum achievable spatial frequency increases from 200 to 550 lines/mm. The improvement of the surface relief amplitude by alteration of the chemical composition is limited due to the fact that both decrease of the plasticizer and increase of the monomer concentrations result in less stable photopolymer layers. In order to obtain further improvement in the spatial frequency resolution a thermal treatment of the layers was implemented. It was observed that baking of the layers at temperatures ranging from 120 to 220 °C at a rate of 1 °C min^-1 makes possible the inscription of surface relief profiles with a sub-micrometre period of 650 nm and amplitude of 15 nm.