Abstract

Holographic dry photopolymers have been studied for almost four decades. They possess many advantages including self-developing capability, shape flexibility, easy processability and low cost over other holographic recording materials such as silver-halide materials, gelatin and poly(vinyl alcohol)-based materials and photorefractive crystals. Conventional dry photopolymers for permanent holographic storage include photosensitive monomer or oligomer, a photoinitiator and a polymeric binder. Some other additives such as co-monomer and a photosensitizer are sometime included to increase their photosensitivity at a desired recording wavelength. Various applications of using holographic dry photopolymers have been suggested and demonstrated so far. These include holographic optical elements, volume holographic data storage, narrowband optical filters, optical intercoime cts, 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 stability are usually required to make these applications practical. In this paper a new type of holographic dry photopolymer system, nanoparticle-photopolymer composite,¹ is described. Inorganic (silica, titania or zirconia) or organic (hyperbranched polymer) nanoparticles having a large refractive-index difference from a formed polymer are dispersed in (meth)acrylate or epoxy monomer to increase Δη as well as to suppress polymerization shrinkage at the same time. Characterization of the volume holographic storage capability and photonic lattice structures using the nanoparticle-photopolymer composite system are also described.

© 2007 IEEE