Diffraction efficiency and form factor effect of holograms

Subject of study. The influence of the form factor effect on the diffraction efficiency of holograms in various holographic materials is studied. Aim of study. The aim of the study is to review publications on the analysis of the diffraction efficiency of two-dimensional and three-dimensional holograms depending on the shape of the recording beams. Method. Holographic exposure of photosensitive media makes it possible to register the formed interference pattern in the medium in the form of periodic modulation of the refractive index, surface relief, optical absorption coefficient, or other parameters. The measurement and analysis of the diffraction efficiency showed its dependence on the degree of modulation of the recording medium and the shape of the recording beams. Main results. Based on the results of the review, it can be concluded that it is important to consider the cross-interaction of two nonlinear effects—the nonlinearity of the diffraction efficiency and the exposure nonlinearity over the hologram field. Manifestations of this cross-effect have been noticed by other authors but are often explained by other reasons. Its non-detectability and hidden effect can be explained by the manifestation only in the presence of two indicated nonlinearities simultaneously with the presence of local maxima in them. In all other cases, the form factor effect disappears. The areas of manifestation of the form factor effect in holographic experiments are shown as an effect that generates restrictions on holograms’ main “power” parameters, such as diffraction efficiency and optimal exposure. The manifestation of the form factor effect is immanent in the holographic recording of complex images because it cannot be eliminated completely but can only be weakened in the initial section of the exposure. Practical significance. Along with the indicated restrictive properties, the form factor effect allows in-situ measuring of holograms’ kinetics recording with high accuracy without involving additional complex equipment. This method was patented. Its influence can be significant; the form factor in holography cannot be attributed to small corrections of the main result. It manifests itself in the main “power” characteristics, similar to the fundamental manifestation of the form factor in the gravitational interactions of irregularly shaped bodies or interatomic interactions.