Optimisation and coupling of high-performance photocyclic initiating systems for efficient holographic materials

International audienceFor fabrication of diffractive optical elements or for holographic data storage, photopolymer materials have turned out to be serious candidates, taking into account their performances such as high spatial resolution, dry processing capability, ease of use, high versatility. From the chemical point of view, several organic materials are able to exhibit refractive index changes resulting from polymerization, crosslinking or depolymerization, such as mixtures of monomers with several reactive functions and oligomers, associated to additives, fillers and to a photoinitiating system (PIS). In this work, the efficiencies of two and three component PIS as holographic recording materials are analyzed in term of photopolymerization kinetics and diffraction yield. The selected systems are based on visible dyes, electron donor and electron acceptor. In order to investigate the influence of the photophysical properties of dye on the holographic recording material performance time resolved and steady state spectroscopic studies of the PIS are presented. This detailed photochemical studies of the PIS outline the possible existence of photocyclic initiating systems (PCIS) where the dye is regenerated during the chemical process. Simultaneously, these visible systems are associated to fluorinated acrylate monomers for the recording of transmission gratings. To get more insight into the hologram formation, gratings' recording curves were compared to those of monomer to polymer conversion obtained by real time Fourier transform infrared spectroscopy. This work outlines the importance of the coupling of the the photochemical reactions and the holographic resin. Moreover the application of the PCIS in holographic recording outlines the importance of the photochemistry on final holographic material properties: here a sensitive material with high diffraction yield is described. Indeed, this work outlines the importance of the coupling between the photochemistry underlying the radicals photogeneration and the holographic resin