High fidelity holographic recording with cyclic allylic sulfide monomer

摘要

A new photopolymer system for holographic recording is presented. It exploits the free-radical ring opening polymerization of a cyclic allylic sulfide monomer, 7-methylene-l,5-dithiacyclooctan-3-yl acetate (MDTOA). Such a system allows for the transferring of the holographic pattern with great fidelity, independently on the rigidity of the host matrix. For this purpose, experiments were carried out in a cellulose acetate butyrate matrix using Irgacure 784® as photoinitiator. The films show excellent optical properties in terms of uniformity and transparency after the bleaching process. The measured diffraction efficiency curves indicate that the written pattern is nearly ideal and it well matches with the theoretical curves. The temporal stability of the gratings is monitored and a decrease of efficiency is evident. Improvements and complete time stability is obtained promoting the formation of a crosslinked network, for which the refractive index modulation is also increased.