We have been working on dichromated photosensitive materials for several years. After investigating the photochemical process in various systems, it appears that the chemical structure of the polymeric matrix plays an essential role in the progress of the reaction that takes place upon irradiation by the laser beams. If the primary photochemical process is always the electron transfer from the matrix to the metallic cation giving rise to chromium (V) and a macroradical, the fate of chromium (V) in the system strongly depends on the chemical structure of the polymer. In dichromated poly(acrylic acid) DCPAA, chromium (V) is an unstable species only detectably by ESR spectroscopy upon irradiation: it disappears after stopping the irradiation very fast. On the contrary, chromium (V) is surprisingly stable in poly(vinyl alcohol) and in gelatin. The first spectral evolution corresponds to the only reduction of chromium (VI) into chromium (V) as evidenced by the presence of an isosbestic point. The subsequent reduction of chromium (V) is a very slow process: the complete transformation into chromium (III) is only achieved after several days. As a result, we were able to estimate the UV-visible spectrum of chromium (V) in the matrix and for the first time, it was possible to quantitatively follow the formation of this species and to draw some conclusion about the complexation sites in gelatin.

Organic molecules with novel optical and electronic properties are of great potential in the development of alternable, high density, and high-speed optical memory deices (OMD) with molecular resolution. During the course of our investigations, we have observed new optical and electric properties of some organic donor-acceptor systems in solution. The result obtained with Proton Sponge (PS)/Tetracyanoquinodimethane (TCNQ) and Phenanthrene/Tetracyanoethylene (TCNE) systems are presented, as they have been observed to provide examples of two extreme cases. The separate solutions of PS and TCNQ in acetonitrile are colorless and exhibit no electric conductivity. When they are mixed, however, the color of the mixture turns green. Its optical absorption spectrum shows a new band in the wavelength region of 600 nm - 900 nm, with a relatively high peak molar absorptivity at 850 nm. The mixture also exhibits large and almost concentration independent molar conductivity, thus indicating that complete charge transfer and charge separation have occurred among all molecules in the solution. For TCNE system, although a new optical absorption band centered at 490 nm has been observed, the electric conductivity of the mixed solution remains zero. The observed complete charge transfer and charge separation, stable charge trapping, and new adsorption band with large molar absorptivity are taken as indicators for the feasibility of developing alterable, high density OMD based on organic donor and acceptor molecular.

An in situ waveguide Raman spectroscopy experiment was designed to monitor structural changes that occurred when a hybrid sol gel glass thin film was irradiated with UV light. Raman scatter was collected from an Ar⁺ laser 514.5 TE₀ mode excited in the waveguide. Insight into the photoinduced changes in the glass was obtained by collecting real time WR spectra as the slab waveguide was irradiated simultaneously with UV light. Photoinduced polymerization of the organic group is linked to enhanced inorganic network formation. Silicon centers are brought closer together as their covalently attached methacrylate substituents oligomerize upon irradiation. This promotes further polycondensation reactions between residual Si-OH and residual Si-OCH₃ groups. The resulting siloxane bonds contribute to the growth of the silicate matrix. This photodensification process leads to volume compaction of the matrix and hence to an increase in the material refractive index.

Photoinduced holographic surface relief gratings have been fabricate din dichromated poly(acrylic acid) films. These gratings are formed in darkness subsequent to the illumination at 442 nm and they are obtained without any chemical treatment or wet processing. The influence of chemical parameters, such as ammonium dichromate and dimethylformamide concentrations, on the holographic characteristics of these gratings have been investigated. Holographic characteristics of the recording medium such as diffraction efficiency as a function of exposure, ammonium dichromate and dimethylformamide concentrations, and spatial frequency are presented in this paper.

A slab waveguide is made by spin coating a thin film of azopolymer onto a glass slide. A surface grating is then optically generated and acts as optical coupler. The structure exhibits resonance coupling as a function of the incident probe wavelength and angle of incidence. The transmission of the film is observed to decrease by more than 50 percent at resonance. The wavelength at resonance in seen to vary linearly with the angle of incidence for small angles.

By electrooptic measurements, with the attenuated total reflection method, we study the angular mobility of azo-dye molecules subjected to a poling electric field and/or to a photoisomerizing optical pumping. We demonstrate the site- to-site variation and the time variation of this mobility. We compare different azo-dye-containing polymer and particularly a new functionalized polyimide. A new experiment permits a spectral and temporal measurement of photoinduced dichroism and is a valuable easy complementary method for characterizing angular mobility. With this experiment, spectral shifts, photodegradation and inhomogeneity of the spectrum of dyes have been demonstrated. New result are obtained on the anistropy in spiropyran merocyanine photoisomerization. By comparing the anisotropy behavior of merocyanine with a theoretical model, we demonstrate the important role of the reverse photoisomerization in photoinduced ordering processes.

The optical reflectivity of multilayers consisting of a metal layer of about 50 nm and a dielectric layer in the thickness range of an optical waveguide gives rise to different resonances. In the metal layer the surface plasmon (SPR) may be excited while in the dielectric layer waveguide resonances can be observed, when the resonance conditions are fulfilled. Resonance spectra can be obtained by varying the angle of incidence with monochromatic light or by varying the wavelength at a constant angle of incidence. The evaluation of the resonance light or by varying the wavelength at a constant angle of incidence. The evaluation of the resonance spectra allows the determination of all the involved optical parameters of the multilayer like layer thicknesses and real and imaginary parts of the refractive indices. Using polymer films in the position of the dielectric films the whole set of interactions of thin polymer films with the surrounding environment. This makes the method interesting for optical sensor devices. Depending on the particular interest low price, compact and selective methods of monitoring in situ processes may be realized based on the combination of the SPR-leaky technique.

New optical fiber sensors for detecting leakage of vapor phase alkanes and gasoline have been studied. When exposed to these vapors, certain rubber-type polymers such as polyisoprene and polyisobutylene cause swelling and their refractive indexes decease depending on the vapor pressure of these substances. Based on this effect, the fiber-type sensor heads were fabricated by coating the swelling polymer as a cladding layer on the fiber core with slightly lower refractive index than that of cladding. When was exposed to vapor phase substances, the sensor head changed its fiber structure from leaky to guided one, and then a large change in the transmitted light intensity was observed in a wide range of the vapor pressure. The response was also found to be reversible and reproducible.

We describe in this paper the design and characteristics of real time, high sensitivity, optical sensors, for the detection of pollutant gases in the atmosphere. Molecular engineering applied to the design of the sensing material leads to good selective and sensitivity in the ppm range when the gas plays the role of a dopant in an organic semiconductor. Methods of preparation and optical design are discussed as well.

Progresses in fiber technology - low NA fibers, graded index fibers, perfluorinated fibers of extremely low attenuation - let expect that polymer fibers find their way from in-house wiring outside to the premise and moreover to the access network. In order to study the application range of these fibers a long term reliability test at different temperatures and humidity conditions has been initialized. This contains an accelerated lifetime test in order to separate thermal activated processes from those of different origin. Different environmental conditions will be simulated, especially adverse ones.The experiments are planned as a round robin test and can possibly contribute to a new concept of standard specification.

A new technique for the optical sensing of dissolved oxygen (DO) is proposed here. It is based on the enhancement in fluorescence yield of TPP dye at (lambda) equals 656 nm, when excited by He-Cd blue laser of (lambda) equals 441 nm in the presence of dissolved oxygen. The sensor head was fabricated by cladding the ARTON fiber core with the poly-4-methyl-1- pentene polymer matrix suitably doped with Tetraphenylporphine dye. This sensor head, when placed in a test chamber and end-pumped by He-Cd laser, generates the intense fluorescence at 656 nm. Its intensity was noticed to increase with increasing the amount of DO. A theoretical model of the sensor response was designed and is also discussed.

We report the formation of polyimide-based H-tree waveguides for a multi-GBit/sec optical clock signal distribution in a Si CMOS process compatible environment. Such a clock distribution system is to replace the existing electronic counterpart associated with high-speed supercomputers such as Cray T-90 machine. A waveguide propagation loss of 0.21 dB/cm at 850 nm was experimentally confirmed for the 1-to-48 waveguide fanout device. The planarization requirement of the optical interconnection layer among many electrical interconnection layers makes the employment of tilted grating a choice of desire. Theoretical calculation predicts the 1-to-1 free-space to waveguide coupling with an efficiency as high as 95 percent. Currently, a coupling efficiency of 35 percent was experimentally confirmed due to the limited index difference between guiding and cladding layers. Further experiments aimed at structuring a larger guiding/cladding layer index differences are under investigation. To effectively couple an optical signal into the waveguide through the tilted grating coupler, the accuracy of the wavelength employed is pivotal. This makes the usage of the vertical cavity surface-emitting lasers (VCSELs) and VCSEL arrays the best choice when compared with edge-emitting lasers. Modulation bandwidth as high as 6 GHz was demonstrated at 850 nm. Such a wavelength is compatible with Si-based photodetectors.

The conversion of incoherent-to-incoherent images by spatial light modulators (SLMs) enables optical information processing and computing applications. The conversion consists of recording an incoherent image and an optical modulation on the same photosensitive element. The coherent readout of the photosensitive element is suitable for processing. DC-PVA is a well-adapted material for incoherent-to-incoherent conversion because of its wide sensitivity spectrum and because it is self developing. Optimization of incoherent and coherent intensities and exposure times is preformed. The spatial frequency of the optical modulation is also optimized. The conversion process is characterized by diffractive efficiency and fringe visibility analysis. Effects on phase and amplitude gratings in the material are investigated. Different recording modes are tested: the grating erasure, the grating writing and the simultaneous erasure/writing. In the grating erasure mode the photosensitive material is first impressed with the optical modulation and then with the incoherent image. The grating writing mode is the opposite process. In the simultaneous grating erasure/writing mode the incoherent image and the optical modulation are capture together continuously or with multiple exposures in the DC-PVA plates. Replacing the incoherent beam with the coherent beam in the same geometric configuration performs a comparative characterization. Another characterization consists of comparing the converted image properties with the properties of an image produced by a direct coherent readout of an incoherent slide. Comparisons between incoherent-to- incoherent conversion of incoherently illuminated slides with collimated or divergent beams or incoherently illuminated objects are shown.

A unidirectional electrooptic modular based on an asymmetric highly multi-mode waveguide coupler is demonstrated. A modulation depth of more than 90 percent is experimentally achieved at 633nm wavelength with an index modulation of 3.0 X 10^-4.

A 5-bit true-time-delay lines device having a packing density of 2.5 lines/cm² with a minimum delay step of 50 ps which can controls antenna array with 9 subarrays simultaneously is designed, fabricated and demonstrated in this paper. The power fluctuation among 32 delay lines is controlled to within +/- 10 percent. A bandwidth of 2.4 THz is experimentally confirmed. TO verify the bandwidth of the device, up to 50GHz optically heterodyned microwave signal is generated, sent through the device, and then detected at the output end.

We present a transmission holographic element that spatially separates the Transverse Electric (TE) and Transverse Magnetic (TM) polarization modes. This element can be used as a polarizing beam-splitter as well as an optical switch. Its originality is that it is compared of two reflection holograms stacked together with index matching glue or liquid. The former hologram is a mirror called 'substrate- mode hologram' (SMH) because of its diffraction angle higher than the internal reflection angle in the substrate. The second hologram is a mirror that only reflects the TE mode in accordance with the coupled wave theory. The main advantages of associating two reflection elements rather than transmission usual ones are a wider angular selectivity peak, a greater wavelength selectivity and the possibility to reach high diffractive efficiency with the SMH for both polarization modes. The high index modulation amplitude in the DuPont Omnidex photopolymer enables the recording of elements with high performance and permits to take benefit of the dry process in order to save the accurate grating geometry associated with desired properties. We propose an original design and discuss theoretical and experimental behaviors for green and red reading wavelengths.

An all solid-state electrochromic smart window employing TiO₂ particulate film and electrodeposited WO₃ film with PEO gel electrolyte with high conductivity has been fabricated. The smart window has been found to be excellent for electrochromism and memory characteristics.

Advances of Russian scientists in the field of the development of irreversible and reversible recording media for holography are discussed. Particular emphasis has been placed on the development of photomaterials for display holography, phototechnology of making holographic optical elements. The result of the study of light-sensitive system and their application in the field of optical memory and processing optical information are presented too.

The optical properties of dichromated gelatin (DCG) as a material for volume holography are close to ideal. The material shows large refractive index modulation, high spatial resolution, negligible absorption, and low scattering. The inexpensive fabrication of large format HOEs is attained by automation of the entire process - film manufacturing, hologram copying, that the master hologram is extremely thin and consists of the holographic layer only. DCG layers, however, can not be easily lifted from the glass or plastic substratum. It is possible to achieve this objective by using other materials. As an alternative to gelatin we investigated the holographic properties of materials that contain hydroxyl, carboxyl or carbonyl groups. The investigated materials are: poly(vinyl alcohol) PVA, poly(acrylic acid) PAA and mixtures of these, such as PVA/PAA and chemically modified cPVA. The subject matter of this paper is the comprehensive presentation of the result of the experimental investigation of the holographic properties of the above introduced materials and their comparison to the properties of DCG holographic films. This comparison includes, but is not limited to the diffraction efficiency, grating strength and the transmission characteristics of the films.

The limitation of the holographic sensitivity of photopolymer materials mostly result from an imbalance between photocrosslinking copolymerization and mass transfer processes. The development of new blends containing acrylate and vinyl ether monomers which undergo hybrid-cure polymerization, makes it possible to evade some of the typical shortcomings of multiacrylate formulations resulting thereof. Self-processing materials exhibiting an holographic sensitivity of up to 200 cm²/J and an energetic sensitivity below 20 mJ/cm² are reported. The improvement of the reciprocity between exposure and holographic intensity opens up attractive prospects for applications requiring holographic exposure shorter than 0.5 second.

It was shown that self-processing photopolymerizable system can be used as holographic recording media in the field of microholography. Gabor holograms were recorded with high intensity single laser pulses. The in-line set-up involved a FD pulsed YAG laser and the pulse duration was about 9 ns. A power per pulse of ca 20 mJ corresponding to an energy density at the sample of 150 mJ/cm^-2 was capable of generation in the emulsion excited species and of inducing an efficient polymerization by a free radical mechanism. Incoherent preillumination of the sample by a suitable UV source was necessary to obtain this result with one laser pulse only. Images corresponding to these phase in-line holograms were reconstructed with fair resolution using an He-Ne laser, a wavelength at which the polymer material is not sensitive. Apart from this, the pairing of similar emulsions with a cw green He-Ne laser was possible. The available power density was reduced down to 0.4 mW/cm^-2 and gratings diffraction efficiencies of approximately 50 percent were achieved for an exposure time of 2 minutes. In that case, the purpose was to design low- cost, unsophisticated and not overly time-consuming manipulations, notably for simple demonstrations or university experiments of holography and interferometry.

We report on the characterization of some photopolymer recording materials based on DC-PVA films sensitized or non- sensitized by some xanthene dyes. The limit of the spatial resolution was determined for different sample preparation techniques. It is well known that the quality of the recorded hologram depends on the spatial resolution of the recording material. A bad resolution will reduce the visibility of the reconstructed wave and damages the reconstructed image. It is therefore important to characterize the spatial resolution of the holographic recording material. In this work we compare the result obtained with two different techniques for preparing the DC- PVA plates. Interference patterns with different spatial frequencies are recorded in the material and the modulation transfer function of each pattern is measured in order to get the limit of the spatial resolution of each material. By the way each sample is characterized by the MTF curve versus spatial frequency and the end-user can choose the well- suited material for this particular application taking into account other parameters such as exposure time, intensity, etc. After the characterization of the materials we test their ability for some applications.

We discuss different materials for recording thick holograms and holographic elements. For material selection we apply various holographic and technological factors. Chalcogenide glasses have good optical properties, low scattering and high resolution in application for IR. Thick gel of dichromated gelatin may be used invisible green-blue light, but holograms are unstable. For hologram recording in visible light we use a polymethylmethacrylate - based material, which has high holographic quality and good stability. We consider the synthesis of this material and describe the method of latent image for selection of optimal composition and additives. We use the special molding method for production of high quality of surfaces. Our recording scheme permits receive large size elements with highly reproducible parameters. To obtain highly uniform holographic elements, very strict control of synthesis process is necessary. Application of this technology is discussed.

In this paper, we discuss our most recent work in 2D nonspatial filtering. A brief introduction describes nonspatial filtering and its relationship to conventional spatial filtering. We then show result from our initial experiments in 2D nonspatial filtering and briefly describe a more advanced design. A variation on the more advanced design demonstrates wavelength-independent operation. We then review our initial findings on adhesives appropriate for implementation of the advanced design and comment on the surface quality requirements of the recording material, a polymer with diffusion amplification. Finally, we compare the robustness and efficiency of nonspatial filters with conventional spatial filters.

Local changes in thickness occurring upon controlled exposure to light of photopolymers capable of storing optical information were investigated. The image that developed as a relief in the photosensitive layer exhibited a complete self-processing character because it did not require any chemical post-treatment. Special attention was given to the effect of the gradient of chemical composition, the volume shrinkage, the gradient of surface free energy leading to mass transfer during the generation of low frequency relief gratings. This imaging techniques provides a high flexibility as regards height and shape of the generated relief. It allows fabrication of both diffractive and refractive optical elements that come increasingly into prominence as the micro-opto-electro-mechanical field expands.

The photoinduced reversible color change in photochromic doped PMMA and PVK films was investigated. Upon UV and visible irradiation, closed form absorbency, in the beginning of the photoreactions, followed first-order kinetic and, then deviated from this order. The rate- constants k_uv of the coloring process, and k_vis of the bleaching process, were determinated. For the two diarylethenes studied, k_uv is much larger in both polymer matrices. However, k_vis is stronger in PVK for fulgide Aberchrome 670. Both rates are identical in PMMA. Photochemical fatigue resistance was studied. For fulgide Aberchrome 670 in PMMA matrix, we found 13 percent disappearance after 10 repeated UV and visible cycles.

Solid state dye doped polymer is an attractive alternative to the conventional liquid dye solution. In this paper, the laser characteristics of Coumarin 1(C1), Coumarin 503 and a mixture of C1 and C503 doped polymethyl methacrylate rods modified with ethyl alcohol are studied under nitrogen laser excitation in a transverse pumping configuration and the variation of gain of the dye in solid medium for different pumping powers are studied. The photo bleaching of dye doped polymer rod is also studied.

The analysis of nonlinear optical effects in organic media, namely generation of harmonics of laser radiation, two- photon absorption, and photoinduced birefringence, is presented. The possibilities of their application for recording and processing optical information as well as for transformation of laser radiation are discussed.

Throughout the paper, the concept of the planar 1D lay-out of kxk-switches and the concept of its compact double- layer/multi-layer counterpart will be presented and experimental results analyzed for k equals 4. The paper presents the construction and treats of the working principles of switching system that can operate with minimum number of stages. A reduction of the number of stages is obtained due to combination of the electro-optic (EO) polymer films on the isotropic substrate. The optical switches are collected in one optical layer and each layer composes of at most two 2 by 2 switches simultaneously active. Poly film doped with azo dye and para-nitro- aniline/polyvinyl alcohol were used for the EO films preparation. Thereby switching is applied horizontally and vertically. The scheme of such a 4 by 4 switch in double- layer technique has been presented.

We report on optical beam self-action in a waveguide made of poly(methyl methacrylate) doped with laser dye DCM upon its upconverted photobleaching produced by radiation of a low power CW He-Ne laser. Nonlinear effects of self-action produce spatially stable beam structures usually interpreted as dark spatial solitons in media with negative Kerr-like nonlinearity. We demonstrate experimentally that the proposed mechanism of self-action is more likely upconverted photobleaching, i.e. photobleaching by short wavelength radiation resulting from frequency upconversion of the primary red laser light. Upconversion is not a multi-photon process. It possibly occurs as a result of inhomogeneous line broadening and excitation of thermally populated higher vibrational energy states in the ground state of the dye molecules. Theoretical model of beam propagation is based on the Shrodinger-type nonlinear propagation equation complemented by the rate equation for photobleaching. The result of simulations are in good agreement with experimental data. Possible applications of the studied effects include photonic switching and optical interconnects.

The methods of organic thin film deposition with determined optical properties include several interrelated steps: the precursor synthesis, which chemical structure takes into account deposition conditions; deposition conditions, which takes into account both precursor properties and film properties needed; additional film treatment. By this approach use, the polymers, dyes, metal- and dye-filled polymers were produced by vacuum and laser evaporation, plasma polymerization, combined methods. Films were studied by VIS, IR, Raman spectroscopy, electron microscopy etc. Many organic compounds with complicated chemical structure can be deposited in vacuum and plasma. These films posses unique properties of precursors. The studies of polymer, dye and metal-filled films for write once read many optical media reveal their good characteristics.

We have used theoretical models to give an account of the photoinduced reorientation of the azo-dye molecules in polymers and the related macroscopic effects that are diffraction efficiency and photoinduced birefringence. Measurements have been carried out for three doped polymers presenting different behaviors according to the writing intensity and the sample temperature. Interpolation of the experimental data reveals that the limiting factor for the amplitude of the diffraction efficiency is principally the temperature of the samples, whereas then the sensitivity of the compounds seems to be only driven by the nature of the dye.