Real-time holographic recording material: NGD

Abstract

In this paper, the real-time effect as well as other primary properties of nongelatin dichromated holographic recording film (NGD) are presented briefly. The real-time diffraction efficiency (RTDE) up to 25% has been obtained in experiment. . INTRODUCWIONIt is well known that the real-time effect of hologram has widely been applicated to holographic interferometry, image subtraction, edge enhancement, character recognition, phase conjugation and other areas. But most materials used in which are some expensive crystals1-. Dichromated gelatin (DCG) real-time effect has also been found and been applicated to these areas recently, the circumstance conditions required during all making process, however, are limited seriously2. Nongelatin dichromated holographic recording film (NGD) presented and developed by us, as compared with DCG, has better real-time effect as well as other merits as were shown in [3]are: stable image, excellent anti-humidity, long shelf-life, stronger surface relief modulation capacity, common making conditions, flexibility, light weight, lci-cost of material and so on. NGD REAL-TIME DIFFRACTION EFFICIENCYNGD uses commercial cellulose triacetate as substrate. At first, chelating agent, which is similar to gelatin in DCG, needed in photochemical reaction process is introduced into substrate by preprocessing, and then, a photosensitive layer (from 2i to 20 jt) laid into the substrate surface is formed by using a kind of dichromated sensitization technology. The thickness of photosensitive layer can be controlled for desired by changing preprocessing parameters.The real-time effect of NGD is investigated by measuring the RTDE of a transmittance grating during exposure. As is shown in Fig.l, since NGD is primarily sensitive to short wavelength within visible range but has no sensitivity to red light, the interference grating is formedwith a He-Cd laser (44l.6nm) as the illuminating source while light from a He-Ne laser (632.8nm)is used to monitor the resultant grating. Experimental geometry is shown in Fig.2. The grating spatial frequency is about 500 cyc/mm, L1, L2 are He-Cd, He-Ne laser, respectively, NGD is recording medium, S is detector. As experimental results, most of these gratings have about 25% RTDE, and the best of which reaches 28%. ME CHANI SM OF RTDEWhen NGD is exposed to light, the hexavalent chrom ions Cr6+ are reduced to the trivalent chrom ions Cr3 + which act to form cross links between the long molecule chains of chelating agent, these cross links called chelate harden the chelating agent creating a hardness differential between the exposure region and the unexposure region, O-8194-0683-X/91/$4.OQ SPIE Vol. 1555 Computer and Optically Generated Holographic Optics (Fourth in a Series) (1991) / 291 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 05/16/2015 Terms of Use: http://spiedl.org/terms