The mechanism of hologram formation in dichromated gelatin.

Experiments have been performed which lead to the conclusion that dichromated gelatin holograms arise as a result of the formation of an air-gelatin interface, with the observed high diffraction efficiencies resulting from the air-gelatin refractive index differential of 0.52 found at the interface. It is postulated that rapid removal of water by isopropanol in the development process creates strains in the gelatin film which are relieved by splitting.

Recording holograms in luminescent materials.

The fluorescein-boric acid glass organophosphor has been characterized as a transient photochromic hologram receptor medium in which an excited electronic state gives rise to the holographic grating. It is shown that the holographic signal depends upon dye concentration, sample thickness, and writing laser power. The decay rate of the hologram, after the writing laser is turned off, is determined by the excited state lifetime of 1 sec, while holographic rise times are in the order of 0.

Phase holograms in dichromated gelatin.

The gelatin-dichromate photosensitive system has been shown to be very efficient as a recording medium for both two- and three-dimensional holographic gratings. Upon development, as much as 33% of incident reading light is diffracted into the first order for the unmodulated thin phase gratings and 95% for the thick holograms. The material can record a grating spacing at least as small as 2600 A, and gives reconstructions comparable with those obtained in 649F film.