Volume holographic recording in nanoparticle-polymer composites with reduced polymerization shrinkage

Abstract

Holographic dry photopolymers have been studied for various applications such as holographic optical elements, volume holographic data storage, narrowband optical filters, optical interconnects, waveguide couplers, electrically switchable Bragg gratings, photonic crystals, head-up/head-on displays and three-dimensional displays. High-contrast refractive index changes Δn with high recording sensitivity and dimensional/environmental stability are usually required to make these applications practical. Recently, we have developed a new class of holographic dry photopolymers, nanoparticle-polymer composites [1], in which inorganic or organic nanoparticles are dispersed in (meth)acrylate monomers. In this photopolymer system the phase separation of monomer molecules and photo-insensitive nanoparticles takes place during holographic exposure, providing high contrast volume holograms [2]. The inclusion of nanoparticles also yields to the suppression of polymerization shrinkage and to high thermal stability of fixed holograms, giving high dimensional and environmental stability [3]. In this paper we demonstrate an order-of-magnitude suppression of polymerization shrinkage of volume holograms recorded in nanoparticle-polymer composites by green light initiated thiol-ene photopolymerization, as compared to our previously reported nanoparticle-polymer composites with multifunctional (meth)acrylate monomers.