Dye molecules are widely used as optical active dopants in polymer (or sol-gel) films designed for integrated optics. A large effort is made to control the orientation of dye molecules, in order to produce macroscopic anisotropy (permanent and reversible for optical memories or transient for polarization holography) or to pole the film for electro-optic applications or for harmonic generation. In this paper, optical methods for inducing orientational order in photoisomerizable molecules are discussed. Three mechanisms are analyzed, the Angular Hole Burning (AHB), the orientational redistribution and the orientational relaxation and the dynamics of their competition is studied. Experimental illustrations are given using azobenzene derivatives (like DR1) in PMMA or in sol-gels. These experiments provide an efficient method for the characterization of the angular mobility of molecules in different host materials and of the long term stability of anisotropy and of (Chi) ⁽²) properties. Preliminary results of a general mathematical model are given: they look very promising for the understanding of orientation mechanisms in a broad variety of materials.

Design of photosensitive systems in the field of UV curing and in the area of imaging science (such as 3D stereolithography, photopolymer in laser-to-plate imaging systems, in holographic recording films or in holographic optical elements) is currently and extensively developed. In previous papers, we have (1) detailed some aspects related to recording media based on a photoinduced polymerization reaction which appears promising to record holographic patterns and (2) presented a very general paper on the different photosensitive systems useful to start the polymerization reaction. The present paper is concerned with an investigation of the excited state processes in selected three-component initiating systems which have been shown to be highly efficient under laser exposure and present a high potential for applications in the laser imaging area.

We have investigated the photochemistry and optical properties of an azo dye-based electro- optic (EO) copolymer, methacrylate-bound Disperse Red 1/methylmethacrylate (MA1). We present a complete picture of the optical properties of the copolymer at wavelengths ranging from 200 nm to 1800 nm with detection sensitivity over 6 orders of magnitude. We describe intrinsic measurements of absorption loss and also describe how temperature and radiation affect absorption loss. Photochemical investigations reveal details concerning photodelineation of waveguides in MA1. Irreversible photodegradation of the azo chromophore proceeds with both visible and ultra-violet radiation and a quantum yield of 2 X 10^-5 is found for 475 nm radiation in MA1.

In our laboratories, we have performed many experimental investigations in order to characterize metal ion doped polymer materials, mainly Dichromated Poly(vinyl Alcohol) DC- PVA) and Dichromated Poly(acrylic acid) (DC-PAA), for their use in holography and nonlinear optics. These systems have been employed for recording volume transmission holograms and fabrication of holographic optical elements (HOEs). Moreover, they are attractive photosensitive materials because of their low cost, self-developing nature and high diffraction efficiency.

The photoredox process occurring between HCrO₄^- and a vinyl monomer (acrylamide or acrylonitrile) leads to the formation of chromium(III) and the polymer as final photoproducts. The primary process is a charge transfer between HCrO₄^- in the excited state and the monomer giving rise to chromium(V) and to an organic radical initiator of the polymerization. The influence of pH, monomer concentration, absorbed light intensity I_a and chromium(VI) concentration on the polymerization rate R_p are reported. Two different domains are detected as a function of chromium(VI) concentration: at low concentration, the process of chain termination occurs by mutual annihilation of the macroradicals whereas at high concentration a process of oxidative termination of the radicals by chromium(VI) is involved. The influence of copper(II) on these different processes is also described.

The fluorescence decay kinetics in the copolymer, poly(phenylmethyl-co-p- dimethylanilinemethyl silane) have been studied by steady state and time correlated fluorescence spectroscopy and three absorbing and emitting species are proposed to explain the complex fluorescence decay behavior. In the case of poly(phenyl methyl silane) homopolymer, excitations have been shown to delocalize over several tens of monomer units, however, in the copolymers discussed here the extent of the delocalization has been shown to be dependent on the degree of substitution of the dimethylaniline side group. In the more highly substituted copolymers the excitations are shown to be confined to almost a single monomer unit by the electron donating nature of the dimethylaniline side group. A simple geometric distribution of chain lengths is used to predict the delocalization length of the excitations.

The analysis of the results concerning the influence of the molecular organization of microdispersed photosensitive systems upon their properties has been performed. The dependence of characteristics of silver halide recording media and of a number of nonsilver ones of the molecular organization of the structure of the matrix and photosensitive elements has been represented. The investigations of Russian scientists in this field have received special attention.

A liquid crystalline monomer was photopolymerized under a variety of conditions by both free radical and cationic processes. Comparison of the polymerization rates and the polymer formed by the two mechanisms gives insight into polymerization in ordered phases. The polymerization exotherms generated by the free radical polymerization in the ordered cholesteric nematic and isotropic media were compared to those generated for a similar system upon polymerization in smectic and isotropic media.

Dichromated poly(vinyl alcohol)-xanthene dye (DCPVA-XD) systems have been employed as real-time holographic recording materials. In this paper, holographic characterization of dichromated poly(vinyl alcohol) with fluorescein (Fl), eosin Y (EY) and Rose Bengal (RB) is presented. In addition, a systematic ESR spectroscopic investigation was also performed on these systems. The photochemical evolution of Cr(V), Cr(III), polymer radical and dye radical in these systems has been monitored and a comparison is made.

The mission of the ARO is to seed scientifically sound and technologically important efforts which will enhance Army capabilities. Results of prior research activities have led to major changes in Army operations. The development of the laser provided a completely new capability to precisely measure the range to the target, and to designate targets. The Army's capability to fight at night was a direct result of scientific studies dealing with semiconductor materials and photoelectronic phenomena for image intensification.

A trimolecular liquid crystalline mixture of monomers was photopolymerized while being subjected to macroscopic orientation via surface contact or continuous application of a magnetic field. Polymerization kinetics were not influenced by the macroscopic orientation, and crosslinked networks were rapidly produced. Both IR dichroism measurements and x-ray diffraction analysis indicated that oriented networks were generated when polymerization was conducted from a nematic phase.

A short review of all the types of organic polymer photoconductors is given from the point of view of semiconductor physics and status and prospects of application in photonics are evaluated.

We present a new type of planar optical interconnects; the transverse holograms. With this type of interconnect, one dimensional, input light distribution is converted into a one dimensional output light distribution via holographic pattering along the direction of the optical wave propagation.

Interconnection length and packaging density are important parameters in channel-waveguide- based photonic integrated circuits. In this paper, a multiple channel crosstalk model is developed and then applied, together with experimental results, to study the minimum channel separation and maximum channel length in a highly parallel single-mode channel waveguide array (SMCWA). Further investigation of the tradeoff between channel packaging density and interconnection length due to channel cross-coupling indicates that, in order to obtain a desirable interconnection length, it is often necessary to separate the waveguides in the array on the order of several (3 to approximately 7) channel dimensions.

We describe the production and optical characterization of planar dielectric waveguides of the organic polymers Poly-(alpha) -Methyl-Styrene and Poly-Phenyl-Acetylene. Single mode waveguides, at (lambda) equals 1.064 micrometers , were obtained by the use of the spin-coating technique. Propagation losses were measured through detection of the out of plane scattered light are as low as 0.7 dB/cm. The waveguiding films were spun over fused silica substrates that were previously etched in order to obtain two grating couplers with a 0.55 micrometers period. Nonlinear grating coupling was investigated in the case of Poly-Phenyl-Acetylene, with a 70 ps pulsed source at (lambda) equals 1.064 micrometers at high repetition rate (f_rep equals 76 MHz).

Different physical processes and materials for storage of volume phase holograms are discussed, especially oxides and photopolymers. Several holographic techniques for the characterization of material properties with special reference to holographic storage and optical phase conjugation are reviewed: Isotropic and anisotropic diffraction, holographic interferometry, microphotometry, self-diffraction (gain measurements), light-induced scattering and neutron holography.

The recent development of laser diodes emitting in the far red or near infrared range and which exhibit coherence length exceeding a few centimeters has opened new perspectives in the field of holography. However, the availability of recording materials with sensitivity in this spectral region often stands in the way of the development of new concrete applications. In this respect, this paper deals with a photopolymer recording system which shows great promise. Various compositions were optimized in which holograms can be recorded from 647 to 854 nm. Depending on the recording wavelength used, their holographic sensitivities range from 0.5 to 2 cm²J.

Holographic optical elements (HOEs) play a key role in the optical processing and optical computing fields as well as in non-destructive holographic testing studies. The fabrication of such linear and nonlinear HEOs requires high quality recording films; in the search of such a recording material, we studied photocrosslinking colloid systems like dichromated polyvinyl alcohol films (DC-PVAL). Those films gave holograms having a maximum diffraction efficiency value (MDE) of 18% at 488 nm; at 442 nm, we obtained MDE values between 20% and 55%. When adding a xanthene dye, the MDE value may be increased. In the present communication we introduce many new results on hologram recordings with another kind of xanthene dye dichromated colloid film at 442 nm. Also the knowledge of characteristic properties of such xanthene dye DC-colloids films permits us to focus on `How they are usable in engineering applications.'

Holographic gratings recorded by photopolymerization of liquid crystalline monomers have been immediately and reversibly developed, or switched, by application of electric fields. Diffraction efficiency modulation has exceeded 200-fold, with maximum efficiency about 13% in the on state for 10 micrometers samples. Fixing of the holograms in the more efficient state has been accomplished by short exposure to a single writing beam. Microscopic images of the switching gratings recorded on videotape have provided information about grating structure and supported our proposed mechanism for the recording and switching effects.

Research on 3-D optical memory with photorefractive materials is described for ultra-high density/capacity memory exceeding the classical limit of conventional optical memory. In this system bit data are recorded by a focused laser beam as refractive digital bits in 3-D volume. A confocal laser-scan microscope is used for reading the recorded bit-data. In this paper, we show the system and the methods for writing and reading data, the materials we used, and some devices for practically realizing this type of memory. Some experimental examples obtained through the preliminary experiments are shown and the problems to be solved in future research and development are discussed.

Birefringence is the difference in refraction index for different polarization states. Birefringence introduces the phase retardation in the optical system or results in double refraction in the optical path. Injection molded polycarbonate (pc) substrates are widely used as disk substrates for magneto-optical (MO) disks. However, birefringence of the pc disk substrates is still a deficiency for MO recording applications. The resultant phase retardation in the polarization detection system degrades the MO readout signal"2. The double refraction induces additional aberration of astigmatism which both smears the readout of writing pits, and also perturbs the servo signal in servo systems such as astigmatic or knife edge methods. Thus, effective methods applied toward measuring birefringence of pc substrates are essential in controlling the quality of MO disk substrate replications. Conventional methods, e.g. phase compensator or ellipsometer'4 proposed for measuring birefringence of disk substrates do not satisfy all of the requirements. The phase compensator finds it rather difficult in measuring in-plane (normal to the disk thickness direction) birefnngence. The ellipsometric methods are difficult to be set up for measuring inplane birefringence, although it is quite efficient and accurate. Another method,5 using disk tester system to measure both in-plane and normal-to-plane birefringence, is only applicable of using in reflective type disk substrates. The relationship of readout signal and birefnngence of a disk substrate is first derived using Jones matrix in this paper. Both in-plane and normal-to-plane birefnngences ofMO disk substrates are then presented, as measured by the conventional and adaptive method proposed in this study. The data are then applied toward assessing the figure of merits. The implementation as a tool for the fabrication process control of disk substrates is also described.

Functionalized polymers with non-centrosymmetric groups of the diazo-dye type are good candidates as 3-D optical memory materials. The two-photon absorption features relevant to molecular non-centrosymmetry are discussed. A four-wave mixing experiment performed in functionalized polymers reveals the possibility of inducing a permanent grating via two-photon absorption. The effect is used for the storage of a permanent non-centrosymmetry grating.

Optical information can be stored, erased or overwritten on polymer thin films using polarized light. The information is in the form of localized dichroism and birefringence and is read using a low power probe beam. We have measured the efficiency of the writing beam in a number of polymer and copolymer films containing azobenzene dyes as side groups. In this paper we compare the results amongst the polymers we have synthesized. Preliminary results indicate that copolymers may be optimized to allow for the preparation of efficient thick films for erasable optical recording.

Due to the requirements for thermal stability in the fabrication and operation of electro-optic devices, the quest for suitable NLO chromophores and polymers involves more than the search for highly nonlinear materials. We describe here the preparation and characterization of aryl substituted azole derivatives as a class of thermally stable nonlinear chromophores and their incorporation into high temperature thermoplastics as a host-guest array. Criteria for predicting the thermal stability of NLO chromophores are discussed as are the polar order decay properties of various poled polymer systems as a function of temperature.

Integrated optics Raman scattering is used as an autoscopic probe of planar waveguides fabricated from chiral polymer media or fractal nanocomposites of Rayleigh limit gold or silver particles. The latter behave as electric field intensifiers and are used to enhance the third order nonlinear optical response of the composite films. In chiral media, TE or TM modes launched in the waveguides produce polarized Raman scattering that exhibits a complex dependence on the sample preparation conditions. Fractal aggregates of metallic nanoparticles confer unique properties on the optical response of the composite. The cubic optical nonlinearity of the fractal composites is evaluated by quadratic electro-optic phase modulation. (Chi) ⁽³) is enhanced by a factor of 10⁶ in the wings of the extinction spectrum, far from the maximum associated with plasma resonances of individual metal particles. The enhancement is essentially dispersionless in the low energy region of the extinction spectrum of the composite. A fast d-electron response in the metal is thought to be responsible for the enhancement effect.

A novel solution processable, electrically conducting and photocrosslinkable second order nonlinear optical (NLO) polymer was synthesized and investigated. Cinnamoylated thiophene derivative -- poly [3-octylthiophene-co-4-(N-3 thenyl) amino 2-nitro phenol] shows second order NLO activity upon poling. This conducting polymer, when doped with an NLO chromophore, 3-cinnamoyloxy-4-[4-(N,N-diethylamino)-2-cinnamoyloxy phenylazo] nitrobenzene and poled, exhibits greatly enhanced second order optical nonlinearity. The second order NLO coefficient -- d₃₃ of the dye doped polymer was measured to be 18.6 pm/V at 1.064 micrometers and 3.3 pm/V at 1.542 micrometers by the second harmonic generation technique. The NLO properties of the poled and photocrosslinked polymer samples are stable at room temperature. The combination of conductivity and optical nonlinearity in this type of polymeric materials may lead to new photovoltaic and photorefractive applications.

Polymer Lightguides of polyimide and amorphous Teflon are used for the measurement of various vapor concentrations ranging from water to organic solvents like acetone. The physical principles of measurement used are monitoring lightguide birefringence and metal film enhanced leaky mode spectroscopy. Dynamic measurements are used in order to also analyze mixed atmospheres.

Surfaces of PMMA [poly-(methyl-meth-acrylate)] have been modified by two methods of ionizing radiation: ion beam induced polymer structure formation (IBIPS) and light induced polymer structure formation (LIPS). Mask construction is described. Strip waveguides, branches and star couplers were generated. A method of fiber-chip coupling by etched V-grooves in silicon wafers is reported.

The problem of interconnecting a large number of information channels according to a preset law, using an array of reprogrammable microholograms, is considered. The dynamic characteristics of the holograms in the process of retrieving are investigated. Experimental results demonstrating this method of interconnects are presented.

Polymer multilayer waveguide technology was used to fabricate a polarization-independent phasemodulator. Refractive indices and electro-optic coefficient r₃₃ of the materials used (Co. SANDOZ) were determined by waveguide methods.

Coupling between single-mode (SM) fiber half-coupler and polymeric planar waveguide is investigated. Fabrication of fiber half-couplers using a standard polishing block, including a simple arrangement of fixing the fiber on a glass plate with automatic determination of the polished fiber parameters, are shown. Optical power coupled into thin film PMMA and polystyrene waveguides through a uniform coupling region is measured for the cases of matched and mismatched propagation constants in the fiber half-coupler and the waveguides. Also, variation of the coupled power in the thin film waveguide is correlated with the change in temperature for potential use in thermal sensing and switching applications. Characteristics of the SM fiber-to-optical waveguide coupler with a uniform coupling section and the advantages of a tapered or combined uniform and tapered structure of the film waveguide are discussed.

Computer controlled laser beam recording techniques are used for the fabrication of V-shaped grooves in polymers. With a CO₂-laser patterns are recorded which are suitable for the embedding of multimode polymer fibers with core diameters above 300 micrometers . Using a KrF excimer laser in a cylindric lens configuration V-grooves in PMMA are produced, where shape, width and depth of the grooves are highly reproducible and the parameters may be controlled by pulse energy and number of pulses with an accuracy of less than a micrometer. This method appears attractive for mounting monomode fibers.

In this work, the optical spectra and the complex refractive indexes of phthalocyanine (Pc) compounds with different metallic ion and derivative substitution have been studied. The optical recording performances of multilayer films are reported.

Sinusoidal holographic gratings recorded in photoresist exhibit strong phase retardation and can be used as low cost quarterwave plates. It was found that the two most important fabrication parameters are, in order of importance, the spatial frequency and the modulation depth. It is not possible to achieve a sufficient phase retardation into photoresist with a single grating showing no rotation of the incident polarization, but the cascade configuration shows the required phase retardation without diffracted orders and is a good candidate for the fabrication of high quality quarterwave plates.

The elasto-optical behavior of polymers is investigated by measuring the optical anisotropy in waveguides of this material. The influence of temperature as well as mechanical deformation are taken into account as sources of stress induced birefringence. From this knowledge a novel way of acousto-optical modulation is derived and a device is presented. The performance of it is strongly frequency dependent.

This paper investigates the spatial polarization characteristics of real-time holography and two- wave mixing in eosin both in theory and experiment, and we utilize these features to realize optical storage and pattern recognition.

Langmuir-Blodgett (LB) films of tetra-nonyl phthalocyanine copper (TNPcCu) were prepared and annealed at different temperatures. Their optical spectra and optical constants were measured, the structural changes of the films were studied by x-ray diffraction. Optical recording properties were measured at a static optical recording tester.

Polymer-based holographic recording materials have been employed by us for holography and nonlinear optics. Recently, we have reported poly(vinyl alcohol) doped with ferric chloride (FePVA) as a recording material for volume transmission holograms. different spectroscopic techniques have been employed to investigate the mechanism of hologram formation in FePVA films. UV-Visible, ESR, FTIR and Mossbauer spectroscopic results are presented and a mechanism involving charge transfer is proposed.

In this paper, we report a graded index (GRIN) polymer waveguide amplifier working at 1.06 micrometers wavelength using Nd-doped photolime gel as the active medium. Fluorescent spectrum at 1.32 micrometers region was also observed for the first time. The polymer introduced is soluble in water. As a result, the chemical compounds containing rare earth ions (REIs) can be mixed with the host polymer as long as they are hydrophilic. But the doping concentrations should be below the level of microscopic clustering which quenches the active ions. There are other quenchers which shorten the lifetime of metastable states of active ions.

We present a thirteen-channel infrared wavelength division demultiplexer based on multiplexed phase-matched volume holograms recorded in a graded index (GRIN) polymer thin film waveguide. Channel center wavelengths ranged from 844 to 976 nm (11 nm channel separation), with corresponding output diffraction angles of 22 degree(s) to 70 degree(s) (4 degree(s) between channels). The device demonstrated diffraction efficiencies from 40% to 65% with an average channel crosstalk of -17.2 dB, which is largely attributable to the spectral width of the Ti:Al₂O₃ laser source. The optical power requirements of the system are evaluated and shown to be well within practical limits.

We report the formation of a graded index (GRIN, n equals 1.4 - 1.6) single-mode polymer waveguide lens on a GaAs substrate. The physical dimension of the waveguide lens is defined by the pre-designed mask pattern. The photo lime gel we used is extracted from animal tissue. When dried, this biophotopolymer is a rigid glass film that shows very little absorption or optical scattering. It is soluble in aqueous solutions and insoluble in most organic solvents such as benzene, acetone, petroleum ether, and absolute alcohol. As a result of this, negative photoresist was used as a masking layer for emulsion sensitization. The recording of the chirp grating lens can be realized either by lithographic tool or by holographic recording.

Small angle x-ray scattering (SAXS) technique has been employed to observe the microscopic structural changes at different stages of photocrosslinking in the holographic recording material: dichromated poly(vinyl alcohol). A detailed account of the SAXS technique is presented and results obtained with synchrotron radiation and Kratky Camera are discussed.

Methylene Blue (MB) and Xanthene (XE) dyes sensitized polyvinyl alcohol have been employed for application of correlation peak detection. Bleaching of the MB and XE sensitized films has been studied in detail. The effect of various amines on the bleaching efficiency has been presented. The dark reversibility of these systems has also been evaluated.

This paper describes a microbend displacement sensor with high sensitivity and wide dynamic range designed on the bases of multimode sensor-oriented fiber. A number of high sensitive sensors have been designed on the basis of microbending induced mode coupling of core to clad modes. Usually these sensors need very accurate alignment of input end face with light source for selective mode excitation. We propose a modified sensor configuration based on microbending induced mode coupling.

A scheme for implementing 4 X 4 2-D perfect shuffle by using HOEs with photopolymers is described in this paper.

This work is devoted to the development of diffractive and quasidiffractive optical elements characterized by the microrelief height ranging from several microns up to 180 (mu) k. The technology of the synthesis is based on a novel physical phenomenon of the substance mass- transfer taking place in liquid photopolymerizable compositions (LPC). Using the proposed method, we fabricated and tested the focusators of laser radiation with a microrelief height of 7.5 (mu) k and the raster elements with quasidiffractive microlenses for the white light.

Holographic rejection filters for eye protection against lasers can successfully be fabricated on DCG-coated glass substrates with excellent performances such as narrow spectral bandwidth, optical densities superior to 4.5 and low noise. However, to protect the eye against shocks a more resistant substrate must be used. Since polycarbonate shows good optical qualities, it appears to be a good substitute to glass. Nevertheless, ways must be found to improve the adhesion of DCG layers onto the hydrophobic material before obtaining the same performances as those shown by filters recorded on glass substrates.

By the means of neutron diffraction experiment a mass transport mechanism during the recording process in holographic storage materials is investigated. In contrast to optical experiments with laser light neutron experiments we have the advantage to separate the influence of the mass transport from other recording mechanism, e.g., electron density modulation. However, to make quantitative statements on the mass density modulation the coherence properties of the neutron beam have to be known. Its characteristics strongly influence the result of the diffraction experiment. In this paper we develop an extension of the diffraction theory for monochromatic plane wave on incoherent radiation.

With the sensitivity of photothermal deflection spectroscopy (PDS), it is possible to detect features that cannot be observed by other means, such as singlet-triplet transitions, weak charge-transfer bands, and weak photo-chemical changes at the surface. The films studied were those commonly used as charge transport materials in organic photoconductors, and are comprised of a small organic molecule and a polymer binder. The PDS spectra indicate the formation of charge transfer complexes between the two components in the solid state. The strength depends on the various combinations and can be correlated to relative energy level offsets between the IIOMO of the small molecule and the LUMO of the polymer binder. Reversible photochemistry resulting from UV exposure can also be detected at the surface.

A new technological approach using dry photopolymer recording material makes it possible to fabricate the relief focusing elements for IR radiation. The formation of the relief structure by self-development takes place in the dark, subsequent to the illumination through the computer generated amplitude mask. No wet processing is required. These diffractive elements exhibit low surface scattering. Dye sensitized polymerization of acrylamide has been found to produce nonlinearity of the relief recording. A diffraction efficiency of about 55% has been achieved for CO2 laser radiation.

The Yamamoto effect and the lateral interaction effect between two metal-insulator- semiconductor-switches (MISS) are discussed in this paper. Utilizing the lateral interaction between two MISS and the photosensitivity of the semiconductor, we have fabricated some experimental optical input shift registers (OISR). The optical and electrical characteristics of OISR have been studied theoretically and experimentally, their fabrication procedure and the experiment results are given as well.

Phase holograms have been recorded on resist films with cw and pulsed CO₂ laser light. The relief-phase recordings obtained due to the thermal process involved are analyzed with He-Ne laser light. Holographic characteristics of the recording medium, such as diffraction efficiency vs exposure and spatial frequency, are presented. The capability of resist films to achieve interferometry and for making blazed gratings is demonstrated.

The principle of optical recording on photopolymer materials (PPM) is based on radical polymerization due to light irradiation. It causes the refractive index change, therefore, a PPM allows the volume phase hologram recording in real time. They are simple in treatment and don't need any additional devices for the recording. The elaboration and investigation achievements of our new patent pure photopolymer GFPM-633A are given in this report. The new material is also intended for volume phase hologram recording by coherent light at wavelength 620 - 680 nm.

Polymers containing nonlinear optical moieties were prepared on the basis of maleic anhydride copolymers. Azo dyes such as Disperse Red 1 (DR 1) were attached to the polymer backbones via esterification, amidization, or imidization. Optimal poling conditions for the side-chain polymers were determined by means of thermal analysis. After electrode poling with a bias voltage of 200 V at a temperature of 185 degree(s)C, the spin-coated samples were slowly cooled down to room temperature with the poling field still applied. The thermal stabilities of the poled polymer films were measured by means of electro-optical (EOTA) and pyro- electrical (PTA) thermal analysis and compared to the respective responses of DR 1/polymethylmethacrylate (PMMA) guest/host polymer samples. Both experimental techniques (EOTA and PTA) are discussed in some detail together with the experimental results.

The commercial manufacturing of large format holographic optical elements (HOE) -- these are used in the fabrication of holographic solar concentrators or for daylighting applications in buildings -- requires inexpensive materials exhibiting high diffraction efficiency, bandwidth and controlled shift of the operating wavelength. Hence, the ideal recording material must possess adequate spectral sensitivity at the wavelengths of present day high power lasers and permit the desired shift of the operating wavelength by means of process control. The material should manifest a predictable diffraction efficiency as a function of the layer fabrication technique, of the exposure, and of the development process and display high spatial resolution and low noise. The properties of dichromated gelatin (DCG) as a recording material for volume holograms are close to ideal. It provides a large refractive index modulation, high resolution, negligible absorption, and low scattering. The holographic film is prepared in the laboratory and extensively tested. The processing of the film after exposure is a sequence of chemical reactions and physical treatments. We report in this paper our experience with large format DCG films on glass substrates and present the dependence of the holographic properties upon the layer preparation procedures and upon the exposure energy. The results for the film development and after-treatment are presented in a forthcoming paper.

Diffusers are playing an increasingly important role in optics as a means to either improve uniformity of light applied for illumination of an object, or to improve visibility of an image created by an optical system from a wider range of angles. Probably the most popular applications of the first kind are milky light bulbs commonly used as light sources in our houses or flat panel displays with backlight illumination used in portable computers. The best known application of the second kind is an ordinary wall used as a screen for slide or film projector. Other examples of this type are diffusers in the view finding systems of some photographic and film cameras and in a variety of rear image projection systems (like microfiche readers or rear TV projection systems, for example). It is obvious, in this context, that demand for diffusers will increase with expansion of such systems.