A novel dry photopolymer for volume-phase holograms

A novel photopolymer for the fabrication of high-resolution volume-phase ho lograms, which primarily are used for holographic optical elements, is repo rted. This photopolymer consists of a thermosetting resin as a polymeric bi nder, a polyfunctional monomer, a photoinitiator, and a sensitizing dye. Th e chemistry to form images is based on the polymerization of an acrylic mon omer initiated by radical species while making the holographic exposure, an d accelerated diffusion transfer of the polymerized monomer with postexposu re baking, and of a bisphenol-type epoxy resin as a binder initiated by cat ions with UV exposure, which are generated through photodecomposition of a diaryliodonium salt-sensitized 3-ketocoumarin dye. Exposure of these photop olymer films to an Ar+ laser beam emitting 514.5 nm light at 60-150 mJ/cm(2 ) and subsequent heat treatment resulted in a refractive index alteration a ccording to the light intensity. With this dry process, high diffraction ef ficiency and heat-stable holograms can be formed. (C) 2000 John Wiley & Son s, Inc.