The success of applications involving holographic optical elements depends on the performance of the recording materials used to form the elements. Selection criteria of a recording material must include not only the usual optical considerations such as achievable diffraction efficiency and optical quality, but also the environmental stability and the ease and cost of manufacture of the elements. Three materials are in widespread use and development for holographic optics applications: dichromated gelatin, photopolymer, and photoresist. Dichromated gelatin forms very high-quality holograms, but is relatively difficult to produce and must be protected from moisture. Dichromated gelatin holograms are in use as head-up display combiners, narrowband filters, and diffraction gratings. Photopolymer is generally easier to use, typically does not require wet processing, and usually has good environmental stability. Photopolymer holograms are in use or under development for several applications including laser eye protection filters, automotive lighting devices, and security holograms. Photoresist forms surface relief holograms that can be replicated by epoxy or, for large production runs, by embossing techniques. Photoresist holograms are used as diffraction gratings for scientific applications, as patterns for fabrication of photonic devices, and as master holograms for security applications such as credit card holograms.

Ultra-fine-grain silver halide emulsions with average grain size of around 10 nm were prepared in our laboratory for true color holographic recording. They were spectrally sensitized with various types of cyanine dyes, and their absorption spectra were measured to study the efficiency of sensitization. Their photographic and holographic characteristics were evaluated and discussed in connection with the results of absorption spectrum measurements. Adequately sensitized emulsions showed M- or J-bands in their absorption spectra at the wavelengths of laser beams for exposure. Dye molecules showing no bathochromic shifts of M-bands in emulsion sols contributed very little to spectral sensitization and seemed situated away from silver halide particles. Each of the red, green, and blue holographic gratings recorded on the laboratory-made emulsion plates showed a higher than 50% diffraction efficiency. But some of the best sensitized emulsions did not show the optimum results in diffraction efficiencies.

Holographic structures have been obtained in porous silicon (PS) by photodissolution of the material in hydrofluoric acid under interferometric illumination. This process can be performed after or during the formation of the PS layer. One- or two-dimensional structures have been easily etched down to the submicron range. The photosensitivity is demonstrated for the entire visible range. Because the dissolution process occurs in the bulk, the thickness of the structure is only determined by the penetration depth of the light in the material, which in the case of PS is about 0.1 to 15 μm (from uv to 600 nm). The technique is generalized to all types of nanoporous silicon. The efficiency of the dissolution depends on the specific area of the porous material and the initial resistivity of the wafer. The structures have been characterized by light diffraction. For this material, photoluminescence allows the topography of the porosity modulation to be determined precisely. These results and the ease and low-cost fabrication of the PS layer make porous silicon a promising material for holography.

Optically written gain gratings in inverted laser media are investigated both theoretically and experimentally. We present a transient analysis, valid in the nanosecond-pulsed regime, that permits calculation of the diffraction efficiency and profile of the gain grating within the medium for both transmission- and reflection-type gratings. Because of the laser amplification experienced by all interacting beams, greater-than-unity diffraction efficiency is achievable. Application to high-speed dynamic holography is demonstrated in flash-lamp-pumped Nd:YAG and compact diode-pumped Nd:YVO₄ solid-state amplifiers.

We discuss the historical origin of the holographic concept in the field of crystallography and its relation to modern applications of similar ideas to the problem of structure completion in macromolecular x-ray crystallography. For structure completion, the identification of the diffracted amplitude from the known part of the structure with a reference wave enables the recovery of the unknown part of the electron density from the diffraction intensities. In this article, we show how this may be achieved by means of a maximum entropy algorithm.

Holography can store wavefields in light-sensitive material. Due to its flexibility and the potential of multiplexing several functions into one element, holography has also been proposed as a recording technique for micro-optical elements. This paper discusses the recording of holograms that perform the basic functionalities (deflection, focusing, and fan-out) needed in micro-optical systems. Emphasis is given to the optimum recording of fan-out elements and high-density multifacet holograms. Successful recording schemes are presented, which are easy to align and therefore are interesting for the fabrication of systems. The potential of holography is demonstrated by recording 10,000 lenslets on 1 cm² in a compact optical system. In addition, several highly efficient fan-out elements have been recorded as volume and surface-relief holograms.

A new photopolymer holographic recording material, ULSH-500, based on cationic ring-opening polymerization, has been further optimized to achieve low transverse shrinkage without sacrificing sensitivity. The extent of transverse (z) and lateral (x) shrinkage was determined explicitly in this study for a range of slant angles in volume holograms recorded to near saturation and in holograms of low diffraction efficiency. The values ΔK_x/K_x and ΔK_z/K_z, which represent the physical material shrinkage in the grating vector plane, were ascertained by (1) direct measurement of the differential angle changes in the reference and signal beam angles necessary to achieve Bragg matching and (2) measurement of the average refractive index. The accuracy of this method was primarily limited by the exactness in determining the angle of peak efficiency in the Bragg selectivity curve. It is demonstrated that the peak angle can be established to within a small fraction of a degree. It is shown that the assumption of anchoring and, thus, uniaxial shrinkage as embodied in the conventional fringe rotation model cannot be applied for the photopolymer ULSH-500 under the recording conditions used herein. It is demonstrated that background uplift in angular selectivity profiles can be attributed to nonuniformity in the grating strength throughout the transverse direction of the recording media, and that the uplift can be reduced to negligible levels by using a low fluence pre-imaging exposure. Calorimetric analysis of reaction kinetics was performed using direct laser irradiation delivered by optical fiber.

This article addresses the reconstruction wavelengths and half-power widths of DCG holograms of various gelatins. Of the gelatins studied (four inert, two active, and one PA), the reconstruction wavelength and half-power width of the PA gelatin greatly deviated from those of the other six. The reconstruction wavelengths and half-power widths of the DCG holograms of the two active gelatins had no significant differences from the four inert gelatins, although the diffraction efficiencies of the active were much higher than the inert gelatins. In addition, the DCG holograms of the PA gelatin had more secondary diffraction peaks than those of the active and inert gelatins. The article also discusses the causes of these differences from the microstructure of various gelatins.

The paper presents a new methodology. Properly controlled sensitometry and analysis are used to unveil microscopic information from macroscopic response. The growth rate concept of the hierarchically coupled driving-force model (HCD-Model) provides an aggregated description that remains flexible enough to simulate sensitometric curves very precisely. By unique parameter identification and coherent interpretation, we obtain a simultaneous insight into interacting subsystems as determined by photoelectronic and ionic processes in combination with silver cluster nucleation and growth. Answers to substantial questions of AgX photophysics may be postponed largely to the end of the investigation if relevant results from quantitative analyses have been made available. The approach is outstanding for studies of latent image formation under realistic conditions such as moderate exposure and properly selected photomaterials.