Photodeformable polymer system for holography.

Abstract

Preliminary work is reported for a novel class of materials that undergoes a controllable change in both thickness and refractive index when exposed to light and then heated. The maximum extent of thickness change is approximately 30%, easily giving rise to relief with depth greater than one-half of a wavelength. The holographic efficiency for the first order in reflection then exceeds 25%. The index of refraction rises in regions where the thickness has been reduced, so the holographic efficiency in transmission is markedly less than in reflection. The spatial resolution of the medium itself is above 4000 lines/mm. The holographic medium is based on copolymers of styrene and variously substituted p-hydroxystyrene. The medium itself is sensitive to short wavelengths, but it can be sensitized to longer wavelengths with a variety of dyes. In experiments performed at 442 nm using a helium-cadmium laser for exposure and perylene as a sensitizer, the dose required for full development was ~1 mJ/cm2.