Review of Materials for Holographic Optics

Abstract

The success of applications involving holographic optical elements depends on the performance of the recording materials used to form the elements. Selection criteria of a recording material must include not only the usual optical considerations such as achievable diffraction efficiency and optical quality, but also the environmental stability and the ease and cost of manufacture of the elements. Three materials are in widespread use and development for holographic optics applications: dichromated gelatin, photopolymer, and photoresist. Dichromated gelatin forms very high-quality holograms, but is relatively difficult to produce and must be protected from moisture. Dichromated gelatin holograms are in use as head-up display combiners, narrowband filters, and diffraction gratings. Photopolymer is generally easier to use, typically does not require wet processing, and usually has good environmental stability. Photopolymer holograms are in use or under development for several applications including laser eye protection filters, automotive lighting devices, and security holograms. Photoresist forms surface relief holograms that can be replicated by epoxy or, for large production runs, by embossing techniques. Photoresist holograms are used as diffraction gratings for scientific applications, as patterns for fabrication of photonic devices, and as master holograms for security applications such as credit card holograms.