The diffraction efficiencies of DuPont's photopolymer OmniDex^R 706 holographic recording material are measured for exposures, incident angles, diffusion-time delays and exposure times. As attaching the material on a glass or plastic plate, unwanted secondary gratings are induced, which make the diffraction efficiencies much lower than expected. In order to eliminate this phenomenon, we change the incident angle between the object beam and the reference beam. Since the polymerization and the photospeed of photopolymers are 1000 times slower than silver halide materials, holograms can be influenced with many kinds of parameter. It was examined the static characteristics and the dynamic characteristics that are related with an exposure time and a diffusion-time delay using the dark reaction of monomer in polymerization. Applying the dynamic characteristics, the diffraction efficiencies of this material were stabilized. As a result, the best condition is achieved when the total input power is 8 mW [exposure energy is 200 (mJ/cm²) in our experiment] and the diffusion-time delay is from one to three minute.

The spectral sensitivity and the enhancement of the energetic sensitivity are important points to the optimization of photopolymerizable materials. We have studied a polymeric system based on polyvinylalcohol as binder, monomers as acrylamide and dihydroxyethylenbisacrylamide and a photoinitiator system composed by triethanolamine and methylene blue. This system was irradiated with an Ar⁺ laser tuned at 514 nm, where this material do not absorb. Obtaining diffraction efficiencies of 55% with an energetic expositions of 500 mJcm^-2. A possible mechanism of initiation of the photopolymerization process has been proposed by the presence of semireduced methylene blue that has an absorption band at 520 nm.

We present a novel method for recording persistent holograms in doubly-doped LiNbO₃. Simultaneous sensitization of the crystal by an inhomogeneous UV beam can result to 32% diffraction efficiency recorded by red light in a 0.85 mm thick sample, while read-out with only red light is non- destructive. Rapid optical erasure by ultraviolet light is possible and light scattering is efficiently prevented.

A large number of strong nonlinear optical and electro optical molecules and crystals are identified recently. With the discovery of the photorefractive (PR) effect and early realization of its potential utility, PR materials are of considerable interest for the development of all optical devices, such as high density optical data storage and image processing techniques. Organic materials are known to show strong electro optic effects. In organic materials, the properties required for the PR effect including photosensitivity, photoconductivity and electro optic response are provided by different molecules. As a result, the properties can be optimized separately, unlike in inorganic PR crystals such as LiNbO₃. This paper describes the utilization of third order non-linearity induced in Xanthene dye doped gelatin and poly (eosin acrylate) & poly (eosin acrylate-co-isobutyl acrylate) films resulting in direct storage without the need for any further processing i.e., no wet chemical or post thermal/photochemical processing are required. With required amount of solvent and monomer in the presence of benzoyl peroxide (initiator), polymerization reaction was carried out under nitrogen atmosphere. Polymer samples were characterized by NMR, IR, FT-IR & TGA. The polymers were soluble in THF, DMSO, DMF & DMAC solvents and form good optical quality films by spin as well as dip coating. Polymer thin films were prepared with different concentrations of polymer solution onto the glass slides. The UV-visible absorption spectra of the spin coated polymer films showed a maximum at 538 nm. In our simplest optical system, Q- switched, second harmonic Nd-YAG laser light at wavelength 532 nm was used for recording. Two beams split from the same laser were made to superpose with path difference less than the coherent length. One of the beam acted as information carrying beam while the other acted as reference beam. In this present study, we report the direction formation of surface relief gratings on photorefractive surfaces upon exposure to an interference pattern without any subsequent processing steps. This paper also explains the mechanisms of photorefractive effect involved in our samples and how optical data could be stored in a few square micron surface area of the film in the form of surface relief Fourier hologram. Scanning electron microscopic pictures proved the formation of surface relief. The surface relief generated on this photorefractive surface has made it possible to prepare a metallic master to achieve mass replication thereby making the commercial introduction of such technology feasible. Reconstruction was easily made with low power cw laser such as He-Ne. The diffraction efficiency of the hologram formed on these films were found to be around 40%.

Holographic polymer dispersed liquid crystal (H-PDLC) material was recently sensitized that is sensitive in the near infrared (800 nm to 855 nm). The compound was based on mixture of an acrylate monomer and liquid crystals (e.g., E7 and MBBA were investigated). In the present work, the angular sensitivity of gratings, recorded in these H-PDLC films, was investigated for various wavelengths. The holographic recording was realized by a diode laser (834 nm), which produced 1000 lines/mm spatial frequency of intensity grating. Significant broadening in the angular selectivity for p-polarization was observed for the formulation based on E7. The half-height width (HHW) of the angular selectivity was approximately 7 degrees (for 850 nm) and 10 degrees (for 670 nm). However, for s-polarization, the same sample has an HHW of about 2 degrees for both. We believe that this behavior is the indicator of a spatial modulation in the shape of the liquid crystals (LC) micro droplets. Droplet's shape should change spatially from elliptical to spherical correlated with (but not necessarily the same) spatial frequency of the light grating. For MBBA based samples, there is almost no polarization dependence and the HHW of the angular selectivity is about 2 degrees. Thus, the shape of the micro droplets is strongly influenced by the chemical composition of the compound used. It has been demonstrated that angular selectivity for H-PDLC compound is strongly polarization dependent. This indicates that the forms and sizes of micro droplets could be strongly modulated along the gradient of light interference patterns.

A novel three-laser-beam technique that can be used to investigate holographic diffraction characteristics of an M- type and a transient dynamic hologram of a hydrated D96N mutant bacteriorhodopsin (BR) film is described in this paper. The method in both experiments is to build up molar concentrations in the M-state before holographic gratings are written. Note that the commonality between these two holograms is the M-state holographic gratings. Hence, a B-state absorption light source, a 532-nm doubled Nd:YAD laser, pumps BR molecules from the B-state to the excited M-state, then the M-state absorption beam, a 413-nm wavelength from a Krypton Ion laser, is used to write holographic gratings in that state. Writing with an M-state absorption laser induces a direct phototransition from the excited M-state to the B-state (ground state). This concept capitalizes on the bilevel BR system, i.e., depleting the ground state with a B-state absorption laser creates molar concentrations in the excited M-state, and vice versa. The reading is done with a 680-nm laser, which is far away from the absorption bands to ensure a negligible erasing effect on the gratings written in the film, resulting a pure phase hologram with high efficiency. The experimental results have shown that response times are in the order of milliseconds, and Bragg diffraction efficiency is close to 7% for this sample. Note that this CW holographic technique is a nondegenerate four-wave mixing.

A general review of the current holographic materials available from the Micron Plant at AO Slavich is presented. In particular certain improvements to the technical parameters of the materials PFG-01 (notably sensitivity) and PFG-03M (emulsion hardness) are introduced. Likewise the introduction of a new 190 micron TAC film substrate for the PFG-01 and VRP- M emulsions will be mentioned and examples of holograms produced on these emulsions will be shown. Reflection hologram color control techniques using emulsion humidity fixing in special oven are presented and the suitability of these techniques is discussed for various regimes. Recommended chemistries that may be employed with each of the Slavich materials will be discussed in the context of Pulsed and CW radiation sources. Finally, contact copying using the PFG-01 and PFG-03M materials will be briefly mentioned.

We discuss the properties of thick holograms on dichromated gelatin (DCG). We consider the synthesis of this material and describe the method of latent image for selection of optimal composition and additives. Thick gel of dichromated gelatin may be used in visible green-blue light, but holograms are unstable. We discuss optical properties of thick hologram on DCG. Control of the parameters and stabilization of this media is essential. Recording schema has been developed which permits receiving holograms with highly reproducible parameters. Application of this technology is discussed.

The subject matter of this report is the development and test of a technology for the industrial manufacturing of large format holographic optical elements (HOEs) for technical applications that facilitates the choice of an operating wavelength between UV and IR and the selection of a desired bandwidth that may vary between tens and hundreds of nanometers. Such requirements are essential for the fabrication of spectrally selective holographic lenses and mirrors for use in photovoltaics and solar chemistry. Large format HOEs are also finding increased application as facade elements in the control of radiant energy in buildings. Data is presented illustrating the methods used to control the shift of the operating wavelength and to adjust the bandwidth of the HOE. These methods are based on the understanding of the structure and properties of the DCG holographic material. For example, the recording of holograms for the blue part of the spectrum requires the use of a filler material to swell the hologram and a specific development process to shrink it subsequently to the desired thickness of the layer. Thus, the required filler material should have the same optical properties as the DCG and should be water soluble. The material should be optically neutral and play no more than a passive role as padding in the hologram fabrication process. A similar technique, based on the permanent swelling of the hologram, is used to shift the operating wavelength of a reflective hologram into the IR and to modify its bandwidth.

The response curve D-Log E is the most important method to characterize photographic emulsions. In this work we present the experimental study using a real time technique that can be applied to the improvement of the holographic properties of emulsions. We have exposured an Agfa Gevaert 8E56HD emulsion with an Argon laser tuned at 514 nm. After it, we measured the transmittance curve when the emulsion was into the developer bath function of time at 20 degrees Celsius. This method gives us the possibility of study the dynamics of different developers as a function of the storage energy. It also provides a way to optimize the composition of developers function of the chemical composition, temperature and other secondary factors as superaditivity and non-linear processes.

The paper presents an analysis of the property of spectral selectivity of volume holograms. Recent developments in holographic materials give an opportunity to vary the hologram thickness in a wide range (from several micrometers up to several millimeters), that allows to achieve magnitudes of spectral selectivity within the range from microns down to parts of Angstrom. In the paper both the two limiting cases are considered basing on the experimental results and theoretical evaluations.

A new Optical Variable Device (OVD) based on an old color photographic technique (Lippmann photography, invented in 1891) is presented. Today, this type of photography can be applied as a unique security device on security documents, such as, e.g., identification cards, passports, credit cards, and other documents where a high degree of security is needed. A Lippmann photograph is very similar to holograms, currently used in this field; a unique recording of each document can be made to achieve a degree of security higher than that with mass-produced holograms. The recording of Lippmann photographs requires a special type of photosensitive medium in contact with a reflecting layer. Panchromatic silver-halide or photopolymer materials can be used and, after being recorded and processed, laminated to security documents. A special type of recording equipment is required. Lippmann photographs are virtually impossible to copy and, certainly, cannot be copied by conventional photography or color copying machines.

The authors discuss the transfer of human figurative imagery originated with a pulsed ruby laser into dichromate gelatin (DCG) emulsion. Human figurative imagery (live subject matter) has been recorded holographically with pulse laser systems, most commonly with pulsed ruby and frequency doubled Yag lasers using silver halide emulsion due to the short end reciprocity failure of other recording materials. Since the DCG reflection transfer is exposed at 488 nm and the silver transmission master recording is at 694 nm, two of the major considerations for transfers is frequency shift and image size in the DCG hologram. As a display medium, DCG holography is conventionally produced in small format recordings. The authors discuss methods for reducing the imagery optically to better accommodate a small-scale hologram. A reduced image, where the projected image is compressed can work within the constraints of a broad-banded DCG reflection hologram (white/pink coloration), whose limitation of depth, about 2.5 to 3' or 5 to 8 cm has made recording of one to one scale human figurative imagery prohibitive. DCG reflection holograms, volumetric holograms, tend to exhibit a short depth of field and the more broad banded (white in coloration) the more severe the chromatic aberrations in the z-axis. The reduction methods offer image compression in particular with the lens system between H1 and H2, in which case the image from H1 is compressed in the X and Y axis and most importantly in the Z axis. The longitudinal (z-axis) reduction shrinkage is square to that of the transverse reduction. The authors consider the visual appeal and increased efficiency in the final transfer DCG hologram to be well worth the effort. A practical approach is emphasized.

In this paper we present the results of our research on the recording of SHSG holographic transmission gratings using the new BB-640 photographic emulsion, a red sensitive ultra-fine- grained emulsion from Holographic Recording Technologies. The exposed plates were processed following a process similar to that optimized by Fimia et al. for Agfa 8E75 HD plates but with the temperature of the bleaching bath modified to 70 degrees Celsius. This increase in temperature improves the diffraction efficiency but does not produce an increase in absorption and scattering, as opposed to what happens in the case of the Agfa 8E75 HD emulsion. The influence of the developer on various holographic parameters is analyzed and discussed.

New holographic recording materials based on photopolymerizable systems have contributed significantly to the recent growth of holographic applications. In this paper we experimentally analyze diffuse-object holograms recorded in a photopolymerizable material. The recording and reconstruction of holograms are in real time without a chemical process and then it is possible to know the performance of these materials when diffuse-object holograms are made and, at the same time, to measure the contrast of them. The holographic images were captured in real time every 10 s and diffraction efficiency and contrast were calculated. In these experiments the influence of the intensity and the beam ratio on these holographic characteristics was analyzed. Our first results show that it is possible to obtain diffuse- object holograms with a diffraction efficiency of 8% and a contrast of 0.93.

The photosensitivity of As_xSb(Ge)_yS_100-x-y (x equals 35 - 45, y equals 0 - 6) films to light with wavelength 488 nm was investigated. The value of photosensitivity was quantified using the results of chemical etching in amine solutions for as-deposited and exposed films. It was found the exposure required to obtain the optimal relief depth, which is from 0.1 to 0.3 micrometer for holographic gratings, decreases with both sulfur and antimony content from about 2 J/cm² for As₂S₃ to about 0.3 J/cm² for As₃₀Sb₄S₆₆. The photosensitivity of the Ge doped films is sharp decreased with Ge content. A model of effect of additives on the change of dissolution kinetics was proposed. It is based on the consideration of a photopolymerization of films leading to the formation of the insoluble network of AsS_3/2 structural units.