The use of heat treatment in the relief-phase holographic structures formation on dichromated gelatin

A new method is proposed for the formation of a relief phase holographic structure on layers of dichromated gelatin (DCG). The method is based on the application of two types of alternative effects on gelatin: structuring using selective light tanning with coherent radiation from a He–Cd laser and destruction by irradiating the layers with short-wave UV radiation. To obtain highly effective holographic relief structures in the region of high spatial frequencies, up to 1500 mm$^{-1}$, a time-shortened water treatment of samples, interrupted by an isopropanol bath, was previously proposed. In this paper, it is proposed to abandon the water treatment of DCG layers and replace it with heating the sample during irradiation with short-wave UV radiation. In the course of experiments, a steady increase in the diffraction efficiency was obtained regardless of the spatial frequency and thickness of the DCG layer, which is explained by the formation of a relief holographic structure due to evaporation and shrinkage of gelatin areas destroyed by UV radiation under the influence of high temperature.