The soi-gei process is based on the mixing of liquid reactants on a molecular scale and the subsequent solidification of the solution into a porous amorphous oxide gel. The porous gel is then heated to give glasses or poiycrystailine solids. Additives can be made to the liquid mixture to give composites. Many new optical materials have been prepared by the sol-gel technique in the past five years. The present status of the scientific understanding of the process is summarized and examples presented of different types of materials successfully developed for optical applications. The enormous potentials of the process are not fully exploited at present. Sol-gei optics promises to be a growing field of science and technology.

The development of chemical processing methods for the fabrication of glass and ceramic shapes for photonic applications is frequently Edisonian in nature. In part, this is because the numerous variables that must be optimized to obtain a given material with a specific shape and particular properties cannot be readily defined based on fundamental principles. In part, the problems arise because the basic chemistry of common chemical processing systems has not been fully delineated. The prupose of this paper is to provide an overview of the basic chemical problems associated with chemical processing. The emphasis will be on sol-gel processing, a major subset pf chemical processing. Two alternate approaches to chemical processing of glasses are also briefly discussed. One approach concerns the use of bimetallic alkoxide oligomers and polymers as potential precursors to mulimetallic glasses. The second approach describes the utility of metal carboxylate precursors to multimetallic glasses.

The sol-gel technique allows preparation of pure inorganic glasses or composite glasses of inorganic and organic nature at low temperature. Incorporation of organic molecules with desired spectral characteristics is the subject of our research. Specific cases include preparation of stable tunable lasers in the visible based on photostable dyes; glasses doped with dyes characterized by double-proton transfer with good separation between absorption and emission; new materials having nonlinear properties; and glasses with dyes sensitive to ambient acidity and basicity. Four types of these glasses are discussed.

Transition metal oxide (T.M.O) gels exhibit extrinsic or specific optical properties. This duality is related to the fact that they can be used as transparent amorphous matrices from which high refractive index is expected, or for their mixed valence behaviour. Titanium or Zirconium oxide based gels have been used as transparent matrices in which large concentration of inorganic (Eu (III)) or organic luminophores (Rhodamine 6G , Rhodamine 640, Coumarine 4) have been incorporated. Several specific optical properties related to Titanium oxide based gels such as electrochromism photoelectrochemistry and photochemistry are also described.

Cylindrical monolithic silica dry gel bodies, up to 250 grams in weight, are routinely produced from alkoxide sols free of colloidal particles, using tetraethylorthosilicate precursor. These dry gel bodies, after sintering in controlled chlorinated atmosphere, yielded clear, bubble free, dense glass rods 3.0-4.0 cm in diameter and 1 5-20 cm in length. Uv-vis--ir spectra, of properly dehydrated and sintered glass samples tested from 1 80 nm to 3200 urn, showed no detectable absorption peak at 2700 nm and a UV band edge at around 185 nm; implying that resultant glasses are reasonably free of impurities and hydroxyl ions. Effect of sol composition on gel ultrastructure was carefully investigated. It was found that by careful choice of sol composition, type and amount of catalyst and aging conditions, it is possible to tailor the gel ultrastructure for ease of drying. For example, we have been able to produce gels with unimodal pore distributions, and average pore sizes in the range from 8 to 300 A and surface area in the range from 150 - 1100 m2/gram. As a result of this ability to tailor gel ultrastructure, including pore size, bulk density and skeletal density of the gel bodies, we have been able to optimize gel ultrastructure to maximize its strength, so that it can withstand capillary forces generated during the drying processes. The result of this preliminary investigation has led us to believe that high quality fused silica glass of much larger sizes can be produced by the alkoxide route; and experiments to scale up the process is under way. Up to date results of this investigation will be presented at the conference.

Pregrooved glass disks were prepared by the application of the sol-gel coating technique; the soda-lime-silica glass disks were coated with polyethylene glycol(PEG)-containing Si02-Ti02 gel films, in which fine patterns were formed by pressing a stamper. The refractive index of the pregrooved layer was matched with that of the glass disks by adjusting the TiO2 content. When the weight ratio of PEG with the average molecular weight of 600 to SiO2-TiO oxides was unity, the pitch of the pregrooves formed was unchanged in comparison with that of the stamper used after the heat-treatment at 350°C, while the land height and the land width of the pregrooves were respectively reduced to 6O9 and 85 of those of the stamper after the heat-treatment. The noise level of the glass disks with the pregrooved SiO2-Ti02 layer was lower by 1-2 dB than that of the disks with pure 5i02 layer in the frequency range from 0.5 to 2.0 MHz. The lower noise level of the former can be ascribed to the agreement in the refractive index between the pregrooved layer and the glass disks.

The effects of the addition of polyethylene glycol(PEG) on the formation of gel-derived glass films in the Si02-TiO2 system were studied, aimed at their application to the optical memory disks. The viscosity of the as-prepared sols increased almost linearly with increasing PEG content. The increase in viscosity of the sols during the storage was retarded with decreasing molecular weight of PEG added and with increasing amount of PEG added. The viscosity increase of the sols during the storage, however, showed a similar temperature dependence, i.e. almost the same apparent activation energy was obtained, in the sols containing different amounts of PEG. These findings indicate that PEG added to the SiO2-TiO2 sols scarcely reacts with the hydrolyzed inorganic species. The hardness of the resultant PEG-containing gel films greatly decreased with increasing PEG content. The gel films containing PEG of the smaller average molecular weight showed the higher hardness and the steeper increase in hardness with increasing the heat-treatment temperature than those containing PEG of the larger average molecular weight. For a high performance in the fine patterning process and densification of the resultant patterned films, PEG of the smaller amount and the smaller molecular weight is favorable, provided the PEG-containing gel films are initially soft enough to emboss fine patterns by pressing a stamper. Incorporated PEG in the Si02-Ti02 gel films decomposed completely at temperatures over 300 °C and had a very slight influence on chemical bondings in the resultant films.

This paper addresses the properties of sol-gel silica in relation to its potential to provide new devices for optical imaging. Although the sol-gel method opens the door to unprecedented levels of purity of silica materials, it is also beset with problems of the achievement of extreme optical homogeneity. The work reported discusses experiences with sol-gel silica intra cavity elements in ion lasers and new concepts of imaging and laser structures based on fabrication via porous gel-silica. A new physical model for etalons is proposed which shows advantages of porous gel-silica over conventional fully dense materials.

Since the basic phthalocyanine structure intrinsically possesses high thermal and oxidative stabilities, phthalocyanines incorporated into sol-gel glasses provide an attractive approach for realizing highly stable nonlinear optical media. Experimental results recently obtained for the nonresonant and resonant third order optical properties of metallophthalocyanines are reviewed in this paper.

Various methods of obtaining fine colloidal precipitates of cadmium sulfo-selenides in Si02 gel matrices are described. These materials, which are of interest in opto- electronic applications, can be prepared by diffusion of various reactants in wet gels. The influence of different preparative parameters on the diffusion characteristics, the possibility of obtaining distribution gradients and, in particular, the interest of sonocatalysis (ultrasonic irradiation) are briefly presented.

The sol-gel process has been applied successfully to the preparation of small-particle-size ZnS, CdS or PbS-doped silica glasses with a significant quantum size effect. Gels prepared through the hydrolysis of complex solutions of Si(0C2H5)4 and acetate of Zn, Cd or Pb were heated at 500 to 900°C, then reacted with H2S gas to form fine microcrystals doped glasses. From X-ray diffraction analyses and transmission electron mlcrographs, these crystals were cubic ZnS, hexagonal CdS and cubic PbS crystal, respectively, and their sizes were 2 to 8 nm in diameter. In the optical absorption spectra, the absorption edge exhibited a blue shift compared with those of the bulk sulfides crystals. Size dependence of energy shift was discussed in relation to size quantization of electron-hole in microcrystals. The nonlinearity was estimated to be 1.5 x i0O esu for 2% CdS doped glass.

CdS-doped Si02 glasses have been prepared through the sol-gel process. A methanol solution of cadmium nitrate and thiourea in a molar ratio of 1:2 was added to the Si02 sol prepared from silicon tetraethoxide. The mixed solution was left for gelation at 50 °C and thereby complexes of cadmium nitrate with thiourea were confined in the gel. The gel obtained was then heat-treated at 350 °C in air for the decomposition of the complexes to CdS, the elimination of residual organics, and the densification. The above process produced the transparent Si02 glasses doped with CdS microcrystallites up to Cd/Si = 0.05. The optical absorption edge of the CdS-doped glasses moved to longer wavelengths from that of non-doped Si02 glasses with increasing Cd/Si ratio. The size of CdS microcrystallites in the glasses was further controllable with the additional heat-treatment at around 400°C in a lO H2S/90% Ar stream. For these CdS microcrystallite-doped glasses, the peak of photoluminescence was shifted to shorter wavelengths relative to the absorption edge of CdS crystal, in agreement with the blue shift of the optical absorption edge; these shifts were indicative of the quantum size effects.

A gradient-index glass rod of about 13 mm in diameter and 20 mm in length with the refractive index difference of about 0.05 between center and perimeter has been prepared by the sol-gel process from a precursor solution consisted of tetramethoxysilane, tetraethoxysilane, boron ethoxide and aqueous solution of lead acetate. A bubble free wet gel of about 35 mm in diameter and 50 mm in length was obtained by adding acetic acid to the precursor solution as a buffering agent. The liquid in the micropores of the wet gel was totally replaced with acetone. Then the compositional gradient of lead was formed in radial direction of the gel by soaking in an ethanolic solution of potassium acetate. A transparent r-GRIN rod of about 13 mm in diameter was obtained by sintering the gel at 550°C.

Gradient index optics will play an increasingly important role in applications such as fax machines, photocopiers, fiber optic couplers and cameras. In this paper, we present an overview of various sol-gel methods for making gradient index materials.

A new technique for producing radial gradient refractive index (r-GRIN) titanium-doped silica lenses has been developed employing a sol-gel leaching method. The obtained lenses possess a parabolic index distribution and give good images with high resolution. They also show high coupling efficiency with optical fibers and enable a low-loss large distance space transmission of light between optical fibers. Furthermore the sol-gel r-GRIN lenses show a high degree of environmental stability as expected for the doped-silica lenses.

The newly emerging field of Nonlinear Optics and Photonics offers tremendous opportunities for optical engineers and materials scientists. The approach used for sol-gel optics i.e. the use of sol-gel processing can play a very important role for the development of novel materials and device structures for nonlinear optics and photonics. In this paper, chemical processing using the sol-gel method is reported for preparation of new composite materials of both a silica glass and a V2O gel with a ii conjugated polymer poly-p-phenylene vinylene up to 50% by weight. The omposite films show highly improved optical quality with large third-order nonlinear optical coefficient, the latter derived from the conjugated polymer. Optical waveguiding through the film has been achieved. Nonlinear optical studies using femtosecond degenerate four wave mixing, optical Kerr gate switching and power dependent waveguide coupling have been successfully performed. Also, to investigate the use of such films for optical recording, a two dimensional grating structure has successfully been produced.

The sol-gel process is a solution synthesis technique which provides a low temperature chemical route for the preparation of rigid transparent matrix materials. The luminescent organic dye molecules, rhodamine 6G and coumarin 540A have been incorporated, via the sol-gel method, into aluminosilicate and organically modified silicate host matrices. Synthesis, laser oscillation and photostability for these systems are reported. The improved photostability of these materials with respect to comparable polymeric host materials is discussed.

When doped with organic dye laser molecules, porous sol-gel prepared silica constitutes a solid state dye laser medium. In this study such media have been shown to exhibit laser action using: (a) a krypton fluoride, 249nm, laser pump producing nano-second laser pulses and, (b) a coumarin 504 (507nm) pump producing microsecond laser pulses. The lasing thresholds were measured as 140kW/mm3 and 1.8kW/mm3 respectively, with lifetimes of 10-20 and 50-100 shots respectively.

Chemical conditions for thorium phosphate gel preparation have been determined. The transparency is of good optical quality and the gel is very stable for a long time. Under drying condition, this gel can give rise to the xerogel which is still transparent. We can also prepare this xerogel by simple evaporation at room temperature of a very concentrated solution of thorium phosphate. From this viscous medium, the xerogel can be obtained in various kinds of shapes : threads, slabs and blocks. Solidification time depends on the final volume desired and spreads from few minutes to several weeks. Absorption spectrum of pure gel and xerogel have been recorded. Gel and xerogel doped with very well known probes like Nd3 and Er3+ were examined to compare their optical properties with aqueous medium of the same chemical composition. Eu3+ doped gel and xerogel were also studied using their fluorescence properties. The optical properties of Cr3 in doped gel and xerogel allowed us to determine the kinetics of hydration sphere modification during the drying period. Finally, as xerogel synthesis takes place at room temperature, fragile organic dye can be used as dopant, so Rhodamine 60 absorption and emission spectra have been studied in these conditions.When, at that time, the xerogel is doped with Coumarin 460 and Th3+,an energy transfer is observed between dye and Th3+ ions, which contributes to enhance the fluorescence of Th3+ ions. Eu3+ behaves similarly. In conclusion, gel and xerogel of thorium phosphate tested with usual probes such as 3d, 4f ions and dyes seem to be very promissing matrices.

The sol-gel method has been identified as a very promising direction to prepare host matrices for trapping photoactive species. A wide variety of such activator are sensitive to environmental parameters and have been used both for sot-gel processing investigation and photoactive materials preparation. Depending on the organic or inorganic nature of the fluorescence probe, different fluorescence effects have to be expected in metal oxide matrix derived from a sol-gel process. Special attention has been given to the interaction between three fluorescent species (Eu3+ , Nd3+, pyrene) and three inorganic matrices (silica, titania, zirconia). Fluorescence phenomena have been investigated related to the nature of the probe and its incorporation mode into the host matrix.

Previous studies have shown that sol-gel matrices are excellent low temperature hosts for various optically-active materials, both organic and inorganic. Optical properties of these composites depend upon such factors as the structure of the matrix and size, shape, and degree of dispersion of the optically-active phase. We discuss factors that control the shrinkage and clarity of silicate aerogel host matrices and report on novel composites in which the optical properties are controlled by solid-vapor and/or solid-liquid reactions within the host matrix.

Sol-gel processing is used to make two new types of silica optics, Type V fully dense silica and Type VI optically transparent ultraporous silica. Type VI silica is an ideal matrix for impregnation with second phases that are optically active, resulting in a hybrid optical material with a unique combination of properties. The processing and characteristics of several hybrid optical devices are discussed including hybrid dye lasers, scintillators and wavelength shifters, transpiration cooled windows, and laser written waveguides. Advantages of the hybrid optical components are discussed along with potential applications.

Shaped microporous silica has been prepared by a sol-gel process. The resulting silicas have 50% open porosity. The open porosity is filled by immersing the shapes in methyl methacrylate (MMA) and polymerizing with ultraviolet radiation. The fully impregnated silica is recovered in net shape. The outstanding feature of the PMMA-impregnated silica is its transparency. There is little loss from scattering because of the nanometer scale of the micro-structure and the similarity in index of refraction for silica and PMMA. The flexure strength of the sillca-PMMA composite has been measured in iL-point bending. The strength increases at slower strain pates because the PMMA provides crack blunting. The composites can withstand thermal shocks up to about 150°C without losing strength. The thermal expansion coefficient for the range 0 to 150°C follows a mixing rule for 50% silica - 50% PMMA. While the mechanical behavior of the composite largely follows that of bulk PMMA, the microhardness is 3 to 5 times greater than for bulk PMMA.

Organically modified ceramics (ORMOCERs) have been prepared with respect to optical applications. The investigations show that materials can be synthesized with interesting properties for a variety of potential applications. They can be used as hard coatings for the protection of optical polymers, e.g. CR 39 or fluorescent dye contaming PNMA. The incorporation of dyes leads to active optical matrices, e.g. fluorescent coatings and the introduction of components with high refractive increments to refractive index numbers n 1.68. For microoptic applications, materials suitable for photolithographic patterning or direct laser writing have been developed.

The synthesis of zirconia modified polymerized methacryloxypropylsilane as a new material with a potential for optical application has been investigated. The material is synthesized by copolymerizing 3-methacryloxypropyl trimethoxysilane and zirconium propylate chelated by methacrylic acid. The methacrylic acid serves as a complexing agent and participates in the polymerization process in order to incorporate the zirconia homogeneously into the polymer. Transparent bulk materials have been prepared by this process.

Molecular dispersions of amorphous siliceous materials doped with organic molecules, TPPS, were prepared by a sol-gel process in which Si(0C2H5)4 was hydrolyzed in neutral solution. An amorphous silica which was doped with TPPS on the order of 1x105 mol/mol Si02 showed photochemical hole burning at 4 K. The TPPS/a-Si02 was heat-treated at various temperatures and the change of optical spectrum were observed as a function of temperature. It was found that the sample was comparatively stable upto 200 °C.

Sol-gel methods offer a number of notable advantages for the synthesis of optical films and coatings. Areas of potential or actual application of this technology range from single layer and multilayer antireflection coatings to embossed planar waveguides and organic-modified oxide materials. The most notable advantages of these wet chemical nethods will be surveyed, as will progress achieved to date in a number of the most attractive representative areas. The technical bases for the success/failure in each case will be considered. Also to be discussed will be the prospects - in both the near-term and long-term - of future developments in the sol-gel synthesis of optical films, as well as the principal technical hurdles which must be overcome in order that such synthesis methods may achieve more widespread use in the future. Finally, a comparison will be made between the microstructures and characteristics of films and coatings deposited using sol-gel methods with those deposited from the vapor phase. In all cases, use will be made of recent advances in our laboratory in the subject area.

Process parameters introduce a wide range of property and behavior variations in inorganic coatings deposited from metal-organic derived solutions. The modifications occur in the molecular, morphological, and the stoichiometric states and present some unique design opportunities for applications in the optical and electronic fields. The nature of the modifications and the processing parameters that introduce the modifications are discussed for the metal-organic derived oxide coatings.

Pursuing our official collaborative ICF-laser search and development program at Limeil National Laboratory (LNL) with the Lawrence Livermore National Laboratory (LLNL) for high damage threshold optical coatings, we have now formally established that Sol-Gel highly reflective coatings prepared from colloids are superior to those prepared from solutions of precursor materials. Thus, single layer coatings of bohemite A1203.H20 have been prepared on fused silica and BK-7 substrates from aqueous colloidal suspensions of hydrated alumina at room temperature. Such coatings were porous and therefore revealed a measured refractive index of about 1.44, lower than the relevant dense material. These single coats when laser damage tested, have exhibited thresholds, under S-on-i irradiation mode (S shots at the same fluence onto a selected site) of respectively i2-i4 J/cm2 with 3-ns pulses and 35-50 i/cm2 with-i6 ns pulses at 30-Hz. Multilayer, high reflectivity, dielectric coatings were also prepared at room temperature by laying down quarterwave-thick, alternating coats of this alumina with silica also prepared from colloidal sol, and having a refractive index of 1.22. To achieve 99% reflectivity 32 to 36 total layers were required. Such HR-coatings revealed damage thresholds as good as those of single layers of the constituting oxides in the same laser conditions.

Sol-gel derived silica, siica-titania, and tantala coatings were covered with a thin metal film and translated across a Nd:YAG laser beam (1.06 jim). The laser energy was absorbed by the metal film, which heated the underlying sol-gel coating. This heating densified the sol-gel coatings, thereby increasing the index ofrefraction of the laser heated region, and forming channel waveguide structures in all three systems. The channels formed by this technique were etched, to remove the undensified regions, which resulted in ridged waveguide structures. The structures were also produced by depositing a metal pattern using photolithographic techniques, and rastering the laser across the entire sample. The refractive indicies of laser densifled and furnace densified silica coatings were similar. Large differences were observed in the indicies oflaser and furnace densified coatings for the siica-titania and tantala systems.

A series of silica gel films were spin-coated on single crystal silicon (c-Si) substrates and their structure was characterized by vibrational spectroscopy. The films were either dried at room temperature or partially densified at 450 0C. Fourier transform infrared absorption spectra have been obtained for each film and they are compared to the spectrum of thermal SiO2 films. The gel films (ca. 150 nm thick) show the presence of residual OH groups, but very little molecular water or organic species and the fundamental Si-O-Si vibrations exhibit shifts toward lower frequencies, compared to the thermal oxide. The Si-O-Si antisymmetric stretch near 1070 cm was narrower for the gels and the shoulder on the high frequency side was stronger. The nature of this feature is discussed based also on oblique incidence transmission and reflection-absorption spectra taken with polarized infrared light.

Spin-on deposited SiO-TiO2 thin films (pure and doped with dyes) are produced. Their optical and mechanical properties are determined and their use for a number of applications is investigated. The spin-on deposited SiOi film has been succesfully doped with coumarin as a colour center and characterized as a waveguide overlay.

Amorphous tungsten oxide layers are deposited via the sol-gel route. Aqueous solutions of tungstate salts (Na2WO4) or chioroalkoxides (WOC12(OPr')2) provide cheap and suitable precursors for the synthesis of W03, nH2O colloidal solutions. Layers of large area can be deposited by spray or dip-coating. They exhibit electrochromic properties and could be used for making display devices or smart windows. Their elecirochromic properties depend on the structure of the oxide network and the amount of water of the W03, nH2O layers. Switching time and stability decrease when n increases due to faster ion diffusion. Optical absorption arising from electron delocalization varies with the crystalline structure of the oxide network. Both the structure and the hydration state of the layers depend on the experimental procedure. It is therefore possible to optimize the electrochromic properties of sol-gel derived layers.

The production of thin films whose refractive index is measurand specific, for use in an interferometric fiber optic chemical sensor, is discussed. The problem of making such coatings has been tackled by a system we have termed the "guest-host" approach, in which an active liquid whose index varies with measurand, is contained within a porous glass host of fixed index. Suitable porous silica-titania glass films have been produced via the sol-gel process. The use of this system enables the index of the glass to be varied, so that the composite index of the liquid filled film can be tailored to that required by the optical system. The sol-gel method developed is based upon the hydrolysis and polymerisation of metal alkoxides, in an acidic aqueous/alcoholic solution. Thin film slab waveguides were deposited in order to measure the light scattering losses, which were found to be typically ''1dB/cm. The porosity of films was studied using a new technique developed in which water adsorption isotherms are plotted using ellipsometry. The pore size was found to be very small of pore diameter in the nanometer range, and the total porosity -1O%. Both of these factors were increased by the removal of residual organic material, using hydrogen peroxide. Finally the use of pH indicator dyes as a liquid fill is discussed, to produce a pH sensor.

Vanadium dioxide thin films have been grown from vanadium tetrakis (t-butoxide) by the sol-gel process. A new method for the synthesis of the vanadium precursor was also developed. Films were deposited by dipcoating glass slides from an isopropanol solution, followed by postdeposition annealing of the films at 600°C under nitrogen. The properties of these films, to a high degree, were a function of crystalline boundaries and crystalline grain size. These gel-derived V02 films undergo a reversible semiconductor-to-metal phase transition near 72°C, exhibiting characteristic resistive and spectral switching comparable with near stoichiometric V02 films prepared on non- crystalline substrates by other techniques. Paralleling the investigation of pure V02, films were doped with hexavalent transition metal oxides to demonstrate lowering of the transition of the transition temperature.

Sol-gel cerium - titanium oxide layers present potential application as transparent counter-electrode (ion storage layer) in electrochromic windows and mirrors using lithium conducting electrolyte and W03 electrochromic coating. The precursor sol, prepared by mixing Ti(OPri)4 and Ce(N03)6 (NH4)2 in ethanol, is initially dark red and becomes transparent after a few days aging indicating the presence of Ce3 complexes. The layers have been obtained by dip coating technique and heat treated at 4509C during 15 minutes.They have been characterized by XRD, SIMS, optical absorption and electrochemical techniques; it is shown that the electrochemical reaction corresponds to a reversible insertion-extraction oflithium ions within a Ti02 amorphous film containing small Ce02 crystallites. At low sweep frequencies the process is controlled by a diffusion mechanism (DLi ≊ 6.4 lOl2cm2/s at 259C). Characterizations of an all solid state electrochromic window/glass/JTO/ W03/ POE-Li N (502 CF3)2 1 Ti02 - Ce02 I ITO I glass I are also presented.

Single and multilayer sol-gel thin films of Ti02-PbO, Ti02-Bi203 and Ti02-CeO2 composition were deposited on glasses using the dip coating technique. The precursors included Ti(OPri)4 chemically modified by acetyl acetone and diluted in PriOH and sols of Pb(OAc)2, Bi(NO3)3 5H20 diluted in acetic acid. The Ti02-Ce02 sol was prepared by mixing Ce NH2 (NO3 )6 in ethanol and then adding Ti (O-iso-C3H7 )4. Structure texture and homogeneity of their main constituants was established by XRD, XPS,SIMS and SEM-EDX techniques as a function of heat treatments.

The sol-gel method using lithium and boron-n-tributoxide as starting materials has been applied to prepare Li2B4O7 coating films on silica glass, silicon and sapphire single crystal substrates. The effects of the amounts of water and acid added to coating solutions, and the kinds of substrate on the crystallization of Li2B4O7 coating films were fully investigated. It was found that a sufficient amount of water is required for obtaining well-crystallized Li2B4O7 films of single phase, the addition of acids such as hydrochloric and acetic acids to the coating solution suppresses crystallization up to 600°C and gives highly oriented Li2B4O7 single phase films on further heating at 800°C.

Ferroelectric thin films including undoped and doped PZT (lead zirconate titanate), BaTiO3 (barium titanate), SBN (strontium barium niobate), KNbO3 (potassium niobate), PBN (lead barium niobate), KNSBN (potassium sodium strontium barium niobate), and LiNbO3 (lithium niobate) were made on silicon and fused silica substrates by a sol-gel process. A heterojunction effect was observed in ferroelectric thin films on both n-silicon and p-silicon through measurement of I- V characteristics, and by the demonstration ofa photocurrent effect. Transparent and preferentially orientated SBN thin films on fused silica substrates can be obtained by applying a d.c. electric field during heat treatment. The films have structral and optical anisotropies as well as photorefractive properties. Two-wave mixing experiment was demonstrated by using these films and a maxmum holographic efficiency of near 1% was obtained.

Transparent strontium-barium niobate (SBN) thin films, 0.3-1.0 pm, have been made by the solgel method. Alkoxide solutions were used as starting materials. Polycrystalline SBN thin films were grown on fused silica, single crystals silicon, and GaAs substrates after firing at 700°C. Dielectric, ferroelectric, and pyroelectric properties of SBN films were observed. Absorption spectra of SBN and SBN doped with 0.3 % Cu ( SBN:Cu) were measured. The photorefractive effect of SBN was demonstrated by a two-wave mixing experiment.

Refractive index values are reported for sol-gel derived PbTiO3 thin-layers as a function of thermal processing conditions. Dense amorphous layers were formed at 350°C (n = 2.35) with crystallization at 450°C (ii = 2.65). A spin-casting method is described for the deposition of coatings. Ellipsometry was used to monitor optical properties as a function of heat-treatment conditions.

The sol-gel processing of lithium niobate thin-layers on silicon from heterometallic alkoxide solutions is described. Advantages of sol-gel processing for low-temperature formation of stoichiometric lithium niobate are discussed. A recyrstallization procedure, involving a bimetallic alkoxide, was developed for the purification of alkoxide solutions. The alkoxide complex contained the appropriate cation ratio for the preparation of stoichiometric lithium niobate. Solvent selection, addition of nitric acid or ammonium hydroxide, and thermal processing conditions were shown to affect the ceramic microstructures. In particular, the solvent system and additives influenced grain growth and porosity in the crystallized layers. Methoxyethanol-derived layers had a grain size approximately twice that observed for the ethanol system. Use of a rapid heating process produced dense layers at 650°C, whereas oxygen treatments allowed for crystallization at 400°C.

Sol-gel processing methods were investigated for the preparation of lithium niobate optical layers. Two alkoxide systems, ethanol and 2-methoxyethanol, were studied. The methods resulted in either randomly oriented polycrystalline layers on silicon or grain-oriented layers on sapphire and platinum substrates. Data are reported for the electrical and optical properties of the layers. In addition to stoichiometric lithium niobate layers, Ti:LiNbO was prepared by the addition of titanium alkoxides to the solutions. Optical data are presented for the Ti:LiNbO3 layers as a function of titanium content.

The results of studies into the interaction between sol-gel prepared silica and 1O.6μm wavelength laser radiation are presented. Hardening of the silica has been measured up to the value for fused silica. The lower densification and upper damage (bloating) thresholds were measured as 4.3 ± 0.2 and 6.3 ± 0.3 J cm ^-2 of surface irradiated. A reflectivity refractometer has been developed to measure the refractive index of sol-gel surfaces and inconsistencies in the surface were detected resulting in variations in point-to-point measurements.

A new laser method is reported for manufacturing of microoptical components including high-aperture microlenses and microobjectives which can be used in fiber-optic communication links, in integrated optic devices, in the laser technique and technology, as well as in scanning optics. The physical model of the local laser thermoconsolidation process is described. The main types of the microoptical elements and their specific parameters are presented.

The results of the investigation of new class of the laser media based on dye solutions impregnated microporous glasses are presented. Based on such media high-effective active elements of tunable dye lasers and passive modulators for solid-state lasers are created.