Recent state-of-art applications of diffraction gratings and stratified materials with one or several modulated interfaces impose specific requirements on electromagnetic grating theory. A review of such applications is presented here with an emphasis on the aspects of the theoretical methods required for their efficiency prediction and optimization. A brief review of the basic ideas of the various electromagnetic theories used is given. The specific domain of validity for each theory is discussed together with advantages and shortcomings. The aim is to serve as a guide in selecting the most appropriate theoretical method for handling specific grating problems.

We present diffraction experiments where the roles of light and material are inverted with respect to usual holography. Atomic matter waves are diffracted at grating structures composed of standing light waves. In contrast to material holograms, our light gratings can be manipulated during the passage of an atomic matter wave, resulting in new diffraction features. We demonstrate similarities and differences between material and light holograms.

In recent years three-dimensional images at atomic resolution have been obtained by holography as well as by x-ray crystallography. In this report we explore the connections between these two methods from a unified point of view. To recover the unknown structure we use mathematical methods developed for the solution of inverse problems. We review relevant experiments and discuss some ideas that may lead to more powerful imaging methods in the future.

A number of interesting and useful interferometric measurements can be obtained by using more than one wavelength. The following report discusses how holography enhances both the possibilities and results obtained from multiple-wavelength interferometry. A discussion of approaches is followed by a number of examples from our own laboratory work in this area. In the first example, two widely separated wavelengths are employed to exploit the dispersive properties of a solution to measure temperature and concentration simultaneously. In this case holographic recording makes phase-shifting interferometry possible with a snapshot recording. In the second example, the use of anomalous dispersion at the resonance of a gas is exploited to measure species concentration. This is accomplished by direct optical subtraction of the two different wavefronts, one at resonance and the other off resonance. Finally, two closely spaced wavelengths are reflected from a diffuse surface and subtracted optically by holography to contour a surface.

Inorganic material systems for archival holographic recording are considered. The emphasis is on bleached silver halide emulsions and CdS and Se colloidal solutions. The bleached silver halide emulsions were investigated to determine the salient parameters that influence photolytic stability and diffraction efficiency. The experimental and theoretical investigations reveal that the silver halide grains, the gelatin matrix, and the gelatin matrix voids are contributing to the holographic storage mechanism. By the adsorption of bromine from the processing solutions on the silver halide grains, it is possible to extend the photolytic stability almost indefinitely. By suppressing the influence of the gelatin matrix and the gelatin matrix voids by chemical processing, it is possible to obtain increased diffraction efficiencies reaching 70%. The colloidal solutions were investigated to determine the basic mechanisms for photodepositing ultrathin surface relief holographic gratings. The results reveal that the photodeposition includes primary photoreduction and secondary adsorption controlled processes. A model is developed to predict the spatial frequency response of the colloidal solutions showing that the recorded spatial resolution is limited by the particle sizes.

Photoactive organic layers, such as photochromic polymers and photopolymers, are investigated for real-time and in-situ holographic recording. The results with photochromic polymers containing spiropyran and spirooxazine dyes revealed that variations in the UV beam excitation and visible recording beam procedures significantly changed the exposure sensitivity and diffraction efficiency. These effects were exploited for all-optical modulation of the holographic gratings and explained by the photochemical and thermal transformations between photochromic stereoisomers. Copolymers of the photochromic spiropyrans were investigated for optical recording with infrared laser radiation at 10.5 and 10.6 μm. Although the recording primarily occurs by thermal bleaching, some nonthermal IR processes are also involved. Holographic recording in photopolymer layers, based on acrylamide monomers dissolved in polyvinylalcohol, is influenced by chemical additives. Specifically, a superadditive sensitization effect of diphenyl iodonium chloride together with triethanolamine significantly increased the exposure sensitivities at 514 nm, by a factor of more than 3 (to about 15 mJ/cm²). Severa formulations produce large enough refractive index modulations so that very high diffraction efficiencies (DE > 90%) are obtained. For certain conditions, under highly asymmetric recording angles, the diffraction efficiency is significantly reduced, and was found to originate from fringe bending due to nonlinear shrinkage. The introduction of crosslinking and gelling agents stabilize the formed grating structures against dimensional distortions.

The properties of volume holograms recorded with speckle reference wave are of interest because they allow high-density information multiplexing and its coding and processing. The results of theoretical and experimental study of angular selectivity for this type of hologram are presented in this article. Several mechanisms are interacting in this case as a result of the joint action of cross modulation grating (diffraction on cross grating) and intermodulation structure (locally recorded speckle pattern). The conditions are determined when the value of the angular selectivity depends either on the cross grating spacing or on the speckle pattern parameters. The strong angular selectivity of the speckle-wave hologram can be observed by its angular detuning in any arbitrary direction. It is demonstrated that observed peculiarities in the character of angular selectivity of the hologram with reference speckle wave can be very efficient for multiple holographic image recording in thick media.

Hybrid imaging systems combine the advantages of silver halide (AgX) and digital photography. The use of cathode ray tubes (CRT) to expose photographic materials allows an interface between the technologies of AgX and digital photography. To optimize image quality, the parameters of the CRT should fit those of the photographic film. Computer-generated test images (density step wedges, color charts, edges, or sinusodial patterns) were written onto different films. A microdensitometer with a charge coupled device (CCD) camera was used to measure modulation transfer function (MTF) and Wiener spectrum for these test images. The color transformation was determined by spectrophotometric measurements. The effect of the CRT film recorder on modulation transfer, noise, and color reproduction is discussed.