Fabrication of computer-generated phase holograms using photopolymers as holographic recording material

Abstract

Photopolymers are studied as holographic recording material for computer-generated phase filters for pattern recognition by optical correlation. The analysis was performed using a copying process with a computer-generated filter, which is produced by means of a high resolution graphic device, as a master. In this work the low spatial frequency response of the photopolymer as holographic material is studied. The copying process used in this work consists of storing the pattern contained in the master in a photopolymer used as a holographic recording material. This photopolymer does not work in real-time, it is possible to store the holographic optical element for a long time because the dye is finished during exposition and the chemical process is not necessary after exposition. We used partially coherent light, from a high pressure mercury lamp. The photopolymer used in these experiments was composed of acrylamide and triethanolamine as the coinitiator, photoinitiated with a dye, yellow eoxine. Components were supported by a film of poly(vinylalcohol). The resulting thickness of the film was approximately 70 micrometers. Diffraction gratings and Fresnel lenses were obtained as phase holograms by index and thickness modulation, monitored with an electron microscope. First order diffraction efficiency achieved was 30%.