Some Possibilities for the Enhancement of Light Sensitivity of Silver Halide Photographic Materials for Holographic Recording by Counter Propagating Continuous- and Pulsed-Radiation Beams

Abstract

1 Fine-grain silver halide emulsion layers are widely used for holographic recording by counterpropagating continuous laser beams. In the case of recording with nanosecond pulse radiation in such layers [1,2], a substantial decrease (by a factor of up to 20) in the diffraction efficiency and light sensitivity is observed. The effect of lowering the speed of silver halide photosensitive materials at short high-intensity exposures (reciprocity failure) is known and it has been described in some works [3][4][5][6].As we showed earlier [7,8], one of the possibilities of enhancing the sensitivity of photographic materials to pulse radiation is increasing the silver halide grain size. However, the diffraction efficiency considerably declines in this case. The determination of the optimal grain size is a complicated problem, since the light sensitivity and the diffraction efficiency are related not only to the size of grains but also to their concentration, physicochemical properties, and exposure and chemical-processing conditions.Previously [8], this problem was studied with the use of special fractional layers prepared for the purpose from the "Kurchatov Institute" emulsion. Five fractions were isolated in which the average grain size varied from 50 to 25 nm; i.e., in the range covering the dimensions of grains of standard holographic materials at 5-10 nm intervals. As a result of this study, we revealed the following.(1) The character of latent image in silver halidebased holographic layers depends on the time characteristics of writing beam and is related to the grain size. 1 (2) The efficiency of holographic recording by radiation with a pulse duration of the order of 10 -8 s increases with an increase in the silver halide grain size.(3) Monodispersity requirements imposed on emulsions are less strict in the case of pulsed exposures as compared with recording by continuous light.Thus, the requirements for materials and chemicalprocessing conditions in pulse holographic recording differ from those in the case of recording with continuous radiation. On the preparation of initial light-sensitive systems and final holographic structure, there is a possibility of enhancing the efficiency of contradirectional recording by pulsed radiation, including that of nanosecond pulse duration.In order to optimize the size of grains, it is necessary first of all to have an emulsion synthesis process that allows the grain size to be finely controlled.In this work, we studied the feasibility of preparation of photographic emulsions with various grain sizes using the process for the manufacturing of photographic emulsions with relatively large grains (up to 50 nm) for holographic recording in cocurrent beams. EXPERIMENTALThe synthesis was conducted using the double-jet emulsification process. Solutions of silver nitrate and halide salts were automatically fed in portions to a gelatin solution. The size of portions was controlled by compressed-air pressure. The stirrer speed was 1000 rpm. The emulsification time of such an emulsion wa...

Development of high-resolution photographic materials of the National Research Center "Kurchatov Institute" for nuclear research

“…According to study data [12], as well as experimental work data [13,14] the number of interstitial silver ions at room temperature in 1 cm 3 of silver bromide is equal to ∼ 8 • 10 14 ions. In the study [15], calculated data on the concentration of interstitial silver ions in silver halide crystals with diameters of 0.02 and 0.03 µm are presented: the number of interstitial silver ions is extremely small and amounts to ∼ 0.6 and ∼ 2 silver ions per microcrystal, even taking into account the near-surface zone, in which there are more interstitial silver ions than in the entire volume of the crystal. This circumstance explains, first of all, the low sensitivity of crystals of such sizes and even the chemical sensitization to which the photographic emulsion is subjected will not be able to increase the sensitivity of such fine-grained emulsions due to the small surface of the grains.…”

“…The technological process for obtaining nuclear photographic emulsions with high resolution was based on the technological regulations for obtaining high-resolution photographic materials for holography in oncoming beams with the necessary changes in the processes of synthesis and sensitization of photographic emulsions [15]. This technological regulation did not provide the necessary concentration of silver halide in the developed photographic materials (up to 80 wt.%).…”