Mechanisms of Generation of Relief High-Frequency Holographic Structures on Dichromated Gelatin Exposed to Shortwave UV Radiation

Abstract—The application of two types of alternative action on gelatin in the layers of dichromated gelatin (DCG) was considered: structuring with the use of selective light tanning by the radiation of a He–Cd laser ($\lambda=440$ nm) and destruction performed by exposure of layers to short-wave ultraviolet radiation ($\lambda<270$ nm). The crucial role of UV exposure of samples in generating high-frequency relief-phase gratings with diffraction efficiency higher than 50$\%$ on DCG layers thinner than 2 $\mu$m is shown. It is noted that the application of traditional treatment methods of DCG layers leads to smoothened relief due to action of surface tension forces at high spatial frequencies. In addition, significant broadening of the domain of registered spatial frequencies (up to 1500 mm${}^{-1}$) for recording relief holographic gratings is achieved by applying the modified technique of gelatin treatment based on reduced time of water procedures and by using the isopropanol baths for quick layer dehydration.