The synthesis and photochemistry of comb-like thermotropic liquid-crystalline (L.C.) polymers containing UV-sensitive cinnamate ester chromophores incorporated as part of the pendant groups is described. The methacrylate monomer was polymerized using AIBN as a free radical initiator. The acrylate monomer was resistant to polymerization under the same reaction conditions. The principle photochemical reactions on photolysis (313 nm) of solutions of the polymer as well as freshly cast films are photocycloaddition and photo-Fries rearrangement of the aryl cinnamate chromophore. Aggregation of chromophores was studied in films as a function of phase type at different temperatures. These results are compared with those obtained from main chain L.C. polyaryl cinnamates.

The structures and spectral properties of several bichromophoric molecules, suitable for optical data processing, are presented. The bichromophoric molecules are composed of an aromatic ring connected by two methylene chains to an (alpha) -diketone moiety. Both the absorption and emission spectra of these compounds can be attributed to a superposition of the individual spectra of the separate chromophores. The critical transfer radia for electronic energy transfer from the aromatic (donor) chromophore to the (alpha) -diketone (acceptor) chromophore was calculated from the spectral overlap between the fluorescence spectrum of the aromatic ring with the absorption spectrum of the (alpha) -diketone chromophore. The results show that this series of molecules is well suited for a mechanistic study of short-range intramolecular electronic energy transfer (intra-EET). The temperature and the molecular structure dependence of the intra-EET efficiency in this series was measured and analyzed for both singlet-singlet and triplet-triplet routes. The results show that the transfer efficiency is strongly temperature and structure dependent, indicating that exchange interaction is responsible for intra-EET between close chromophores in a bichromophoric molecule. The relative contributions of interchromophoric distance and that of the relative orientation of the two chromophores to exchange interaction are discussed.

Dichromated Poly(vinyl alcohol) films with and without dyes and electron donor have been employed for real-time holographic recording and for the fabrication of holographic optical elements (HOEs). The primary photoprocess of the interaction of Cr(VI) with the polymer has been followed under various experimental conditions through esr spectroscopy. The effect of the pH of the coating solution, concentration of dichromate, electron donor and dyes on the evolution of intermediates has been discussed. A suitable mechanism involving the electron transfer from the polymer to Cr(VI) leading to the formation of Cr(V) and polymer radical, which further undergoes reaction to produce Cr(III) and crosslinked polymer matrix, has been suggested.

We have developed a technique for a higher degree of polymerization at the deep area of dental restorative resins by argon ion laser irradiation. We provide an analysis of the resin materials by Raman spectroscopy and Fourier transform infrared spectroscopy.

The exceptional electro-optic properties of poled polymer films, coupled with the power and flexibility of thin film fabrication and photolithographic processing, may make possible the hybrid integration of electronic and photonic devices, combining the processing power of VLSI with a dense, high bandwidth, photonic interconnection and switching network in a single, large format, package. In this paper, we describe the potential applications and benefits of electro-optic polymers for optical interconnection and present a review of some of the relevant progress to date in electro-optic polymer materials and devices. Development of an all-polyimide electro-optic polymer system (cladding/core/cladding) based entirely on commercially available components is described. An integrated optic Mach-Zehnder modulator was fabricated using this material system and used in a 200 Mbit/sec digital signal transmission optical interconnection demonstration. Lastly, a potential increase in electro-optic polymer integration density was illustrated by a proof of concept demonstration of three levels of waveguide structures on a single substrate.

A single-mode polymer-based channel waveguide array with 1250 channels/cm packaging density on a cross-link induced photopolymeric thin film is reported. This array works at 1.31 micrometers and 0.63 micrometers . Curved waveguides with radii of curvature (ROC) from 1 mm to 40 mm were demonstrated. Waveguide propagation loss in the neighborhood of 0.1 db/cm was demonstrated for both linear and curved waveguides. Interconnectivity for various interconnection architectures including cross bar, hypercube, daisy chain and star are further considered. Multiple layers of optical interconnects may be required for an optical backplane involving massively parallel highly distributed computing systems.

An electro-optic intensity modulator using a gelatin-based EO polymer waveguide has been built and characterized. This EO modulator is constructed from a nitrophenol/gelatin guest/host poled polymer system. V_pi and (gamma) ₃₃ of 25 V and 38 pm/V are obtained, respectively. This is the first demonstration of an active EO device using electro- optic gelatin. Integration of the modulator with a traveling-wave electrode structure to increase the modulation speed is under investigation. Preliminary studies have shown electrical modulation bandwidths of up to 40 GHz.

High speed wafer-scale optical interconnections have been achieved using hybrid opto- electronic integrated circuits (OEICs). Polyimide channel waveguides fabricated using direct laser writing (DLW) served as the interconnect media between the high frequency signal sources and the high speed detectors. The 50 GHz optical interconnection reported here could potentially be used in the implementation of sophisticated wafer scale systems such as phased array radars.

Polymer technology shows the potential to fabricate and integrate the basic components of OFDM-crossconnect elements which are important signal processing units in a future transparent optical network. The fabrication and characterization of integrated optical polymer components like power splitters and combiners and polymer directional couplers are presented. The devices are fiber-pigtailed, packaged and exhibit waveguide losses in the order of 1 dB/cm at 1.55 micrometers wavelength. Studies based on guest/host-polymer-systems for application on electro-optic polymer devices are shown and the synthesis and characterization of rare-earth doped polymers for active device applications are reported. Because polymer technology is a conceptional hybrid, a combination of semiconductor and polymer elements on large substrates is proposed. This opens up the possibility for a future large scale integration of optical components to functional devices by a cost-effective technology.

Optical waveguides have been produced in poly-(methyl-meth-acrylate) (PMMA) by ionizing radiation of the surface of polymer solid blocks. Planar and strip structures have been obtained. Dispersion curves of refractive indices have been measured between 458 nm and 1523 nm. Mechanical changes of the surface geometry have been studied by surface profilometry. Chemical reactions within the irradiated volumes have been investigated by ATR-FT-IR spectroscopy. Light guiding properties of the waveguides are reported.

The potential of optical interconnections used in electronic computer systems continues to be a popular area of research. The main applications of optics in interconnection are not proposed to replace electrical interconnects directly, but rather to utilize the different characteristics of the optical solution making architecture changes. In this paper, some improved schemes which can be applied to interboard optical interconnects and some physical design issues and problems are also addressed briefly.

The probability of absorbing a photon by a highly anisotropic dye molecule depends on the orientation of its principal absorption oscillator axis with respect to the polarization direction of the acting light. This will result in more molecules whose absorption axes are parallel to the polarization direction undergoing photoisomerization than the molecules which have other absorption axis orientations. Saturation occurs when all of the molecules aligned in a particular orientation are isomerized so further photoexcitation cannot occur. In this case saturation becomes direction dependent and occurs first in the direction aligned with the incident polarization. We investigate this anisotropic saturation behavior and present a theoretical model which incorporates intensity saturation for describing diffraction from dynamic photoanisotropic organic materials. Numerical simulations of diffraction versus intensity and polarization are provided and compared with the experimental results.

The photochemical behavior of thin films and solutions of main chain nematic liquid crystalline trans-stilbene dicarboxylate polyesters (SDA) is discussed. Observation of spectral differences between solutions and thin films indicates the presence of chromophore aggregation. Hypochromic effects attributed to aggregation of chromophores become more pronounced upon thermal annealing above 40 degree(s) C. Polymer solutions and thin films (above 40 degree(s) C) exhibit the ability to undergo a reversible photocycloaddition reaction.

Polymer coatings are used extensively in optical disk technology, the majority being acrylate based formulations which are transparent and tough. For example, the servo pattern for tracking can be generated by a photopolymer process (2P), where a thin acrylate-based coating system is cured between a `stamper' and a treated glass substrate. In this study, we have extended this technology beyond current servo geometries to generate the small structures (0.6 micron pitch features) that are required for future substrates using the blue laser. The fidelity of replication is measured by scanning tunneling microscopy (STM) techniques. Acrylate based polymer lacquer coatings are also applied (by spin coating) to optical disks and compact disks to provide handling and anti-static protection. The term `corrosion protective coating 1' (PC1) refers to the coating on the film side of the disk and `scratch resistent protective coating 2' (PC2) refers to the anti-static, anti-scratch coating applied to the substrate side of the polymer disk. A number of analytical techniques have been developed to monitor the cure of these acrylate based systems. These include infrared spectroscopy, microhardness, various thermal methods (DMTA, TGA, TGA-MS) and extraction techniques. The usefulness of these techniques is discussed in terms of formulation optimization, cure optimization, and accelerated aging tests that reveal failure mechanisms.

Optical information can be stored, erased, or overwritten on azo 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 investigated this image storage phenomenon on a series of polyacrylates and polymethacrylates containing azo aromatic groups on the side chains. The monomers are obtained from commercially available azo dyes. The polymers are amorphous and have high glass transition temperatures. We present a model for the writing and erasing process and investigate the physical origins of the parameters which influence the properties of the recording medium.

Azo dye polymers have been investigated as polarization holographic recording and all-optical modulating media. The use of azo dye polymers is limited by their intrinsic low response time. Different dyes and fabrication techniques have been utilized to enhance the material's speed. A relatively new modulation technique utilizing the nonlinear Fabry-Perot effect in attenuated total internal reflection (ATR) geometry is compared to the conventional transmission type modulation geometry. In the ATR case, a small change in the index of the polymer causes a shift in the angular spectrum of the Fabry-Perot resonances, thus enabling us to modulate a probe beam with an external pump beam. Both modulation speed and contrast ratio are greatly enhanced using this technique. Experimental results are presented, and the limits of both methods are analyzed. The ATR method is also useful in characterizing thin (less than a few microns) polymer films, for studying photo-induced index changes. Future applications, such as optically addressed spatial light modulators and nonlinear optical processing applications, are discussed.

The process of local holograms recording on organic photothermoplastic (PTP) materials and the influence of their characteristics on the quality of registration are investigated. The original simultaneous method of the local holographic recording on the PTP materials by IR-laser heating supplying qualitative Fourier-holograms recording of the analog and digital information is described. The usual simultaneous method of PTP-recording is characterized by exponential growth of diffraction efficiency in time. Experimental results demonstrating the possibility of a linear case of diffraction efficiency growth in time on the PTPM allowing increase of the time of surface relief development and the value of holograms diffraction efficiency are shown. Also, the process of local multiplexed holograms recording on the PTPM by the developed method is studied. Using the developed simultaneous method there were recorded two-dimensional fourier-holograms in step-by-step procedure on the PTP-disk carrier. The possibility of holographic PTP-disk based data storage realization is discussed.

The reversible photoisomerization of azobenzene derivatives is known for its anisotropic properties. We study the dichroism and the anisotropy induced by a linearly polarized pump in DR1 doped PMMA films and in a copolymer of PMMA and DR1. We demonstrate the competition of three processes, the angular hole burning (AHB), the orientational redistribution, and the orientational relaxation. The three processes are included in a theoretical model which can be simplified by using symmetry properties (isotropic polymer matrix): the time behavior of anisotropy is well explained by this theory. In the last part, we demonstrate a novel method for poling azodye-containing films, at room temperature, by optical pumping in the presence of a dc electric field: large (chi) ⁽²) are obtained. In the guest-host system, when the pump is switched off, the greatest part of the photoinduced anisotropy and of the orientation is destroyed by the orientational relaxation (non exponential relaxation with a rate from seconds to hours). On the contrary, in the copolymer, there is almost no relaxation and it is possible to write and erase information in the form of molecular alignment. Similarly photoassisted poling produces a quasi permanent (chi) ⁽²), in the copolymer (a r₃₃ of 5.7 pm/V have been measured, 2 days after poling).

Ultrafast optical response in several polydiacetylenes (PDAs) with different side-groups and morphologies has been investigated by femtosecond absorption spectroscopy. Several nonlinear optical processes, i.e., excitonic absorption saturation, hole burning, Raman gain, inverse Raman scattering, optical Stark effect, and induced-phase modulation, have been observed and the mechanisms are discussed. The relaxation from photoexcited free excitons to self-trapped excitons (STEs) has been observed in both blue- and red-phase PDAs. The time constant is estimated as 100 - 150 fs. The decay of STEs in the blue-phase PDAs is nearly exponential with time constant of about 1.5 ps at 290 K and about 2.0 ps at 10 K. The decay curve in the red-phase PDAs substantially deviates from exponential function. It is fitted phenomenologically to biexponential functions with time constants of slightly shorter than 1 ps and about 5 - 10 ps. These two time constants correspond to relaxations to the ground state, respectively, from the unthermalized (hot) STE and from the thermalized STE.

Because of their excellent optical properties, a variety of polymethacrylates with pendant NLO-chromophores has been prepared and investigated by different research groups. The method normally used for the synthesis of these polymers is the free radical polymerization of the corresponding methacrylates with NLO-active side groups. However, the NLO- chromophores, usually large conjugated molecules with an electron donor and an electron acceptor substituent, often contain a number of functional groups, e.g., nitro- or azo groups. These may act as retarders or inhibitors in a free radical polymerization. So in many cases the yields are not quantitative and the molecular weights are quite low. We present an alternative method for the preparation of polymethacrylates with pendant NLO-chromophores, the polymeranalogous esterification of poly(methacryloyl chloride). In a first step, reactive prepolymers are prepared by the free radical polymerization of methacryloyl chloride (MAC1) or by copolymerization of MAC1 with methyl methacrylate (MMA). These prepolymers are esterified using NLO-active side groups with a hydroxy-terminated spacer. Well defined, high molecular weight polymethacrylates with high dye contents can be prepared by this method. A copolymer with 19 mole% of azochromophores exhibits an electro-optical coefficient of 9 pm/V at 1300 mm after poling, whereas 19 pm/V (1500 nm) were measured for a polymer with 90 mole% of NLO active azobenzene side groups. In addition, the novel method provides easy access to some novel copolymers with both NLO-active azobenzene units and photocrosslinkable cinnamoyl groups.

A crosslinkable side chain NLO-polymer of the bis-azobenzene type and an AB-type main chain NLO-polymer of the sulphonyl-tolane type have been synthesized and characterized with respect to their curing and electric poling properties. NLO-susceptibilities d₃₃ of 11 pm/V and 7.5 pm/V, respectively, have been measured after initial relaxation and proved to be highly stable. During poling, transient SH-signal and square of poling current showed similar temporal behavior. Thus transient poling current can be considered to be a useful probe to monitor and to control the poling process. Direct current electrical conductivity was found to be strongly temperature dependent for both materials.

Langmuir-Blodgett (LB) films of tetra-nonyl phthalocyanine copper (TNPcCu) were prepared. The structure of TNPcCu LB film has been studied by x-ray diffraction and IR reflection absorption spectroscopy. The results show that the TNPcCu LB film forms an ordered structure, in which molecules are arranged in an orderly fashion with phthalocyanine rings oriented nearly perpendicular to the substrate surface and perpendicular to the lifting direction. The optical absorbance at 740 nm of TNPcCu LB film has a hysteresis behavior during heating and cooling. Dipoles of TNPcCu molecules are oriented in an orderly fashion and their vibrations in phase cause the formation of aggregates. When the temperature increases, the dipoles change the ordered orientation into the disordered one, the aggregates are destroyed and the absorbance at 740 nm decreases. When the temperature reduces to the room temperature, the dipoles recover their ordered state, the aggregates restore and the absorbance at 740 nm increases. The reversible phenomena of optical absorbance may be applied to the optical recording devices.

Photo lime gel has become increasingly important because of its potential for use in integrated holographic elements. However, it has been a passive optical component. An electro-optic modulator with nitrophenol and gelatin has been constructed and demonstrated for the first time. The transmission spectrum of nitrophenol/gelatin shows an ultrawide optical bandwidth, from 340 nm to 2800 nm. A relatively stable and large electro-optic effect, (gamma) ₃₃ equals 10 - 40 pm/V, was observed at 632.8 nm. This result indicates that both passive and active integrated optical devices can be fabricated onto the same polymer thin film to form a fully polymer-based miniature integrated optical circuit.

A computer controlled laser beam recording technique using the CO₂ laser radiation at 10.6 micrometers is demonstrated. Multimode lightguide patterns with dimensions in the range of 100 micrometers to 1000 micrometers may be recorded in polymer films or polymer substrates. In the adequate exposure range smooth patterns may be obtained. A model for the etching of PMMA by CO₂ laser radiation is presented.

This paper deals with two-wave mixing in eosin doped gelatin film. Some chemical and physical properties of eosin are shown. The basic two-wave mixing equation and real-time holographic characteristics are discussed. The higher order diffraction is observed. The experimental results also are given.

Using index matched polymer lightguides the optical anisotropy of planar polymer films is measured with an accuracy (Delta) (Nu) <EQ 10^-5. The investigation is performed with heated guides in the range of 40 degree(s)C to 110 degree(s)C. An anomaly of (Delta) (Nu) (T) at the glass transition is found. This method may be used for the determination of the glass transition of films in the thickness range of optical lightguides.

Fluorescence properties of the methyl methacrylate solutions of two kinds of aromatic methacrylate monomers: 9-methyl,10-methacryloyloxymethylanthracene and 9- methacryloyloxymethylanthracene were studied. The concentration of anthracene fluors in methyl methacrylate corresponding to the maximum fluorescence yield has been found, and some parameters describing the excitation and deactivation of the excitation energy of the studied system have been calculated. Next polymer rods have been prepared by copolymerization of methyl methacrylate and two studied fluors of anthracene. The absorption and emission spectra, fluorescence lifetimes, quantum efficiency, and Verdet constants were measured for the obtained polymer rods. The studied anthracene fluors can be useful, at small concentrations, as wavelength shifters in polymethyl methacrylate-core polymeric optical fibers whereas higher concentrations of anthracene fluors can be used to get some enhanced magneto-optical properties of the polymers.

There is a growing interest in applying polymers for integrated optics. ARROW waveguides basing on the Fabry-Perot effect exhibit a number of outstanding features compared with conventional waveguides. The theoretical ARROW concept based on leaky waves is discussed. Planar ARROWs realized in a polymer multilayer system by simple technologies have low loss (0.39 dB/cm) and can be made well-matching to a fiber field. Lateral confinement by ARROW-effect has been demonstrated experimentally.

Strip waveguides have been fabricated in a thin film consisting of a mixture of poly- (methylmethacrylate) (PMMA) with a UV-sensitive photoinitiator. The film is deposited by spin-coating on a PMMA substrate. As an example for a sensor application, the waveguides were doped with the pH-indicator dye bromophenol blue, which changes the optical behavior of the lightguide in interaction with a humid environment like an aqueous liquid or a gas.

In complex optical arrangements many holographic optical elements (HOEs) play a key role in the optical processing and optical computing fields as well as in non-destructive holographic testing works. The fabrication of such linear and nonlinear HOEs require high quality recording films; in the search of such a recording material we studied dichromated colloids 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 50% and 60%. When adding a dye, rosa bengal, the MDE value reached 79% for specific conditions. All of those results were obtained in real-time holography and the recording films were free of any chemical development. In the present work we introduce many results on hologram recordings in dichromated dye-casein films at 442 nm; those results are compared with others works on DC-PVAL films. Also, the knowledge of characteristic properties of such DC-dye casein films permits us to focus on `how they are usable in modern engineering applications. '

Dynamic global interconnections between processors in massively parallel computers are a highly desirable feature. Such as photorefractive materials can be used to store holographic gratings that implement interconnection links between individual processing elements of two distinct planes. In this paper we detail the energy transfer between two coupled beams writing holograms in EOSIN film. A type of holographic routing architecture which uses a LCLV is presented. Spatial polarization characteristics and temporal modulation coupling are investigated.

The complex investigations of optical and electronic properties of organic molecular semiconductors are described. It is shown that the process of photogeneration in these compounds passes through the initial formation stage of molecular excitons which can migrate through until an annihilation, capture, or an interaction with traps occurs. The diffusion length of exciton migration is determined, the self-capture processes of excitons, charge carriers, and also processes of carriers captured by deep traps are investigated. The nature of anti-Stocks luminescence, conditioned by annihilation processes at K > 1 cm^-1 and double-photon absorption at K < 1 cm^-1, is determined. Electron structure is studied by means of the photovoltaic current spectroscopy method. The double-photon processes with total and half energy levels common for all substances investigated are found. On the basis of IR-absorption spectra similarity and due to the existence of similar non- interferential enlightenment in the metal-benzene-containing molecular semiconductor junctions Fermi-level energies are predicted for these semiconductors.

In this paper, we report the first graded index (GRIN) polymer waveguide amplifier working at 1.06 micrometers wavelength using Nd:photolime gel material combination. 8.5 dB gain was observed using a 2.2 cm waveguide length with Nd+++ concentration of 1.03 (DOT) 10²⁰/cm³. A tunable Ti:Sapphire laser was used as a pumping source. The success of this demonstration together with the previously reported results on GRIN polymer passive and active devices, provide us the full capability of integrating a monolithic polymer- based integrated optical circuit.

Various components needed for optical backplane applications have been demonstrated from gelatin-based polymer integrated op[tic material. An array of waveguides have been realized with packaging density as high as 1250 channels per cm and loss of 0.1 dB per cm. A 1-to-8 Y-junction splitter and a 32 x 32 star coupler have been fabricated using photolithographic techniques. The unification of the star coupler and a modulator array is for backplane optical interconnects is under investigation.