Advance in the comprehension of the microstructuration by light of polymerizable materials

Abstract

Light structuration has proved to be a promising way to achieve high storage densities. Different types of polymers were proposed : photopolymers like PMMA, photochromic polymers or photopolymerizable systems using inhomogeneous polymerization of one or more monomers. In this paper, we present experimental investigations on an acrylic formulation in which interference patterns are stored through a polymerization reaction, giving rise to thick phase holograms with high diffraction efficiencies and low scattering noise. Gratings with fringe spacings ranging from 0.2 to 5 ?m were recorded. The formulation was suited to be polymerized by illumination around 500 nm. Improvement of the material was possible by taking into account all the optical data characterizing the gratings and the data obtained through UV-Visible spectroscopy or by AFM-PFM analysis (a powerful method of investigation of the local mechanical properties and topography). In particular, diffusion processes were generated by the concentration gradients due to an inhomogeneous disappearance of dye and monomer molecules in the reactive medium. The coupling between polymerization and diffusion processes was studied in order to characterize the photoinduced microstructuration.