Design optimization is very important to achieve high performances of integrated optical devices. For accurate designs, detailed information on the characteristics of slab and channel guides made in glass substrates must be known in relation to their fabrication conditions since these waveguides often form the basic units in more complicated waveguide structures used in devices. This paper outlines the characterization and modeling procedures of such waveguides, and presents the methodology of design optimization of waveguide devices. In particular, the beam propagation method (BPM), combined with the effective index method (EIM), is discussed. The variational technique combined with the effective index method is also discussed.

The authors report the fabrication of high-silica, low-loss three-waveguide couplers (3WC) on Si by a combination of flame hydrolysis deposition (FHD), photolithographic patterning, and reactive ion etching. The device has been designed using the first-order perturbation theory, in order to achieve single-mode operation and to predict the beating length. Simulation of the device has been performed using the beam propagation method. SiO2-P2O5 glass has been employed as core material. P2O5 has been used to increase the refractive index of silica, as well as to decrease its sintering point. The sintering process has been optimized in order to achieve completely sintered, bubble free, low-loss films, preventing the evaporation of the P2O5 as well as the warping of the substrate. The devices have been characterized in terms of insertion loss, power splitting ratio and spectral response. 3WCs with multiple number of beating lengths have also been considered in order to assess the modulation of their spectral response with increasing interaction length.

Multilayer SiO2-TiO2 coatings were deposited on soda-lime and silica glass slides. The coatings on silica substrates were deposited using differently prepared solutions and were heat treated at different temperatures. The waveguides thus produced were characterized and the effects of the chemical preparation procedure and thermal treatment were evidenced. Strip optical waveguides were also fabricated by a laser densification and chemical etching technique.

Using the Na+-Ag+ ion exchange technique, the monomode waveguide for 0.633 micrometers wavelength can be obtained on the surface of K9 glass. In order to know about the refractive index and thickness of the guiding layer, two different wavelength lights were adopted to measure the mode effective index with the prism coupler, and the iteration method was performed to solve the normal eigenvalue dispersion equations. The coupling coefficients between different modes with the reaction of grating were discussed by an equivalent method. The simple results were obtained for the coupling coefficient of TE-TE, TM-TM and TE-TM conversion. The Bragg diffractive gratings were fabricated on the surface on the monomode glass waveguide by the electron beam writing system and ion reaction etching technique. It can be used as light beam splitter or deflector in a Mach-Zender interferometers, TE-TM mode divider, and components for optical interconnection. The experimental results are presented.

New possibilities for glass and glass-ceramic materials for integrated optics are shown. Formation questions of planar waveguides by the ion exchange method on the basis of transmitting, controlling, and recording glassy materials are considered. Examples of various controlled waveguide elements on the basic active glasses are presented.

The authors report on optical investigation of CdSe-microcrystallites (MCs) embedded in glass and grown diffusion controlled to create MCs near the stage of nucleation having small radii (approximately equals 1.6 nm) and a symmetric size distribution. Room temperature measurements of (i) absorption bleaching and its kinetics at resonant MC-excitation using frequency doubled single ps-pulses from YAG-laser, and (ii) spectral hole burning at different delays in the ps-time scale, before and after a surface passivation of the samples by hydrogenation to remove MC- glass interface states responsible for the carrier transfer into the matrix, have been performed. After passivation, higher bleaching values, a slower recovery, and a blue shift of the DTS signal are obtained. A kinetic model including three levels and a fast carrier capture into the glass matrix is discussed to explain the observed nonlinear optical behavior.

Recent experiments regarding the nonlinear optical properties of germanium diselenide glass in thin films and bulk forms are presented. The observed effects are optical bistability without external feedback, laser-induced diffraction patterns, and phase conjugation. These effects are investigated using a 25 mW He-Ne laser at 632.8 nm. The above-mentioned effects show common features, the main one being that they are reversible provided that a certain irradiation power is not reached. Above this threshold the effects are permanent given sufficient exposure time. The recording resolution of the system is diffraction limited below the threshold. The underlying phenomenon responsible for the intensity-dependent refractive index change is believed to be due to photostructural reordering and reorientation of the material.

Semiconducting microcrystallite-doped silica-glass films were prepared by the rf-magnetron sputtering technique using a composite target consisting of a SiO2 plate and semiconductor chips. The semiconductors doped were GaAs, InxGa1-xAs, CdSe, CdTe, CuCl, Si, Ge, and so on. The structure of those microcrystallites (MCs) was investigated with high- resolution transmission electron microscopy (HRTEM), x-ray diffraction (XRD), small angle x-ray scattering (SAXS), and EXAFS. The MCs had a spherical configuration 20 to 100 angstroms in diameter. The average size of the MCs was completely controlled by the deposition condition and the postannealing time. Clear lattice images observed in the HRTEM photograph suggested that the MCs had a similar structure compared with the bulk crystal. The blue shift of the optical absorption edge could be observed for all of the samples. This seemed to probe the quantum size effect. Concentration of the MCs estimated by x-ray photoelectron spectroscopy (XPS) was more than 10 mol%. This value was one or two orders in magnitude larger than that of SDGs prepared by the melting and quenching method. The results of EXAFS measurements suggest that the microscopic structure in the MCs was almost the same as that of bulk crystals except for their surface. By SAXS measurements, an average interparticle distance in the microcrystallites could be estimated for the first time. Waveguiding behavior was also reported for the sputtered CdSe microcrystallite-doped glass film.

Optical glasses doped with II-VI semiconductors are attractive for nonlinear guided-wave devices, due to the combination of several factors such as the nonlinear optical properties, the low cost, and the ease of fabricating optical waveguides. The authors report on the ion- exchange process used to manufacture waveguides in different commercial samples, which have also been the subject of structural characterization.

A technology for monomode slab and strip waveguide fabrication in semiconductor-doped glasses (SDG) is presented. On this basis, directional couplers consisting of both parallel (DC) and bent (BC) couplers of strip waveguides were realized. The optically linear and nonlinear behavior of these devices is described.

Nonlinear optical and electro-optical properties of glasses doped with CdS and CdSe microcrystals are investigated. Nonlinear bleaching and darkening of absorption with recovery times up to 5 ps have been observed. Strong modulation of transmittion of these glasses have been observed. The mechanism of microcrystal ionization under interband optical excitation is discussed.

CdS(x)Se(1-x) semiconductor-doped glasses are studied by means of optical techniques such as absorption, emission, and Raman spectroscopy in order to demonstrate the low dimensionality and quantization effects associated with the presence of CdS(x)Se(1-x) microcrystallites in the glass matrix. By applying simple models to our experimental results, it is possible from either absorption and luminescence or Raman spectra to calculate the effective dimension of microcrystals; these values very well agree with transmission electronic microscopy data. Moreover, by using a pump and probe technique, the authors have studied the absorption changes in CdS(x)Se(1-x) microcrystallites, resulting in the shift of the absorption edge and in the bleaching of the excitonic resonance when the pump intensity is increased.

Optical nonlinear properties of As-S and As-Se chalcogenide thin films are reported for different time scales of the irradiation source.

The thermal and optical properties of a new series of fluoride glasses suitable for active fiber applications are presented. The glasses are based on barium, indium, gallium and zinc fluorides, and in the presence of LuF3 and PbF2 they exhibit a critical cooling rate of 16 degree(s)C min-1. The lowest fiber attenuation is found to be 0.5 dB m-1 at 2.7 micrometers . Compared to fluorozirconate glasses, their infrared transparency is shifted nearly 1 micrometers toward longer wavelengths. By means of Judd-Ofelt calculations and lifetime measurements on Er3+ doped samples, the multiphonon emission rate for this hose is investigated and compared to fluorozirconates.

A detailed study of the ultraviolet loss spectra of germanosilicate preforms and fibers is reported. The fiber samples had peak losses of the order of 10 dB/cm, which was several orders of magnitude lower than in preform samples. All spectra could be described by a number of previously observed absorption bands, many of which had been associated with particular defects in germanosilicate glasses. The incorporation of phosphorous as a core codopant eliminated a loss band centered at 325 nm in as drawn fibers. The effect on the ultraviolet absorption spectra of increasing doses of irradiation from an ultraviolet fiber- coating curing-lamp source and also the change in fiber absorption before and after writing a 35% reflection grating are presented. The results are not consistent with the previously proposed model for photosensitivity based on the Kramers-Kronig mechanism.

Transmitting ultraviolet (UV) light (Ephoton > 3 eV) through optical fibers in many cases causes additional attenuation increasing with exposure time and light intensity. High- energy UV photons interact with defects in the glass structure, causing absorption bands. These mechanisms limit the applicability of quartz glass fibers in demanding applications. Currently reported measurements do not give any information about changes in the transmission of the fiber when exposed to intense UV light. To obtain these data, the transmission of optical fibers is measured during and after UV irradiation in the spectral range from 200 nm to 350 nm wavelength. These data are used to calculate the transmission changes due to photon glass interaction. To investigate the influence of UV light (deuterium lamp) on the attenuation characteristics of optical fibers, the authors produced different fiber qualities regarding UV performance. The results obtained from these measurements lead to a deeper insight into the mechanism of defect generation. UV light not only creates defects but is also able to anneal defects. Some models of this defect creation and annealing are discussed. Based on these models, UV-improved optical fibers are produced, showing less photon-induced attenuation.

A new variant of the MCVD method for the fabrication of polarization-maintaining single- mode optical fibers has been studied. The method is based on the usage of screens to form a necessary temperature field for gas-phase etching by fluorine liberating gas. The fibers of various structures with beat length 5 mm and best value of h parameter 5.10-5 m-1 at 1 micrometers have been prepared by this method.

This paper presents a review of the effects induced by ion implantation in silica glass and in SiO2 films on silicon with particular emphasis on optical modifications and new compound formation. The formation of silicon oxynitrides and nitrogen oxides in surface layers as a consequence of nitrogen implantation was investigated by using different techniques as XPS, SIMS, and optical methods.

It has been reported in previous works on the LPD (liquid phase deposition) method that SiO2 film deposition could be made by utilizing the chemical transition from supersaturation to saturation in silica dissolution in H2SiF6 aqueous solution. In this study, the supersaturated state was obtained and maintained by employing the dependence of silica solubility on H2SiF6 solution temperature without a reaction initiator. As for the influence of the process parameters on SiO2 film properties, it came into notice that a dense film structure was obtained in the deposition at higher solution temperature (around 60 degree(s)C). As a result, transparent and crack-free thick SiO2 film over 10 microns was obtained by this advanced LPD method.

Multicomponent fluoride glasses in the PbF2-ZnF2-GaF3 (PZG) vitreous ternary system have been prepared by vapor phase deposition. The thermal stability of the deposited glass was improved by adding stabilizing agents (AlF3, NaF, LiF, InF3). The thin films, deposited on different substrates (fluoride glass, fluoride single crystal, metal, and silica glass) have been characterized by x-ray diffraction. Differential scanning calorimetry (DSC) and secondary ion mass spectroscopy (SIMS). The quality of the film, adherence, and homogeneity was controlled by scanning electronic microscopy (SEM). The optical characteristics of the film and PZG glass are given: the visible-infrared (VIS-IR) window is 0.3-8 micrometers and the refractive index 1.59+/- 0.2 depends on the lead content. Mn2+ doped films (up to 3 mole % MnF2) are optically active: Mn2+ exhibits a broad luminescence band at 560-570 nm (orange). The achieved film thickness varies from 0.5 to 80 micrometers , and the refractive index gradient approaches the required geometry for planar waveguides (doping of the film with lanthanides is in progress).

The thermal properties of the tellurium halide glasses, the TeX glasses, are greatly improved by introducing a trivalent element As. Tg as high as 150 degree(s)C can be obtained and the glasses still transmit up to 18 micrometers . Vitreous thin films have been deposited on different substrates, using the sputtering techniques. Mono-index fibers and fibers having a core- cladding structure have been successfully drawn. The typical attenuation for the first fibers is less than 5 dB/m and for the second fibers is less than 7 dB/m.

Environmental temperature variations cause stresses to develop in structures that contain materials with different coefficients of thermal expansion. Such a condition often exists in glass encapsulated diodes used in the electronic systems. The situation is further aggravated by the metallurgy of the diodes in the form of stresses due to corrosion--the stress corrosion effect. A third factor that introduces stresses in the encapsulated diodes is due to the design of the glass encapsulation. A combination of these factors led to a failure of glass encapsulated diodes and were identified in a recent study conducted at the Technology Support Division (TSD), Electro-Optical and Data Systems Group of Hughes Aircraft Company. A judicious selection of the encapsulating glasses, its properties, and the design of the seal becomes an important factor in the fabrication of a hermetically sealed diode. This paper highlights such failure mechanisms and describes the desirable properties and design requirements of sealing glasses used for encapsulating the diodes.

Abstract not available.

Glasses with composition corresponding to bismuth germanate crystals have been prepared. All these samples, by means of an appropriate heat treatment, crystallize. Where possible, the kinetics was studied by DSC isothermal runs. The photothermal deflection technique was applied to glasses and polycrystalline materials in order to elucidate the influence of the structure on their thermal properties and to consider them as possible candidates for application in non linear devices.

The forming and sintering of fumed silica powders is an interesting route for the preparation of large, very pure or doped silica glasses with a precise geometry. The processing from the shaping of a porous compact to the sintering of transparent silica glass can be successfully investigated with optical spectroscopy. As only the dielectric function DF (a dielectric function is the square root of the complex refractive index) characterizes the material, the vibrational bands were calculated from reflectance measurements. In compacts of fine particles, the topology cannot be neglected. Therefore, the models describing topological effects are briefly reviewed. With these model calculations it could be proven that new bands in the compacts and the significant shifts in the reflectance spectra during sintering are mainly caused by topological effects and that changes in the glass structure play only a secondary role.

The verification of a rapid and accurate method of penetration viscometry utilizing a commercial thermal mechanical analyzer with slight modification is described. The viscosity of a National Bureau of Standards Sample Glass No. 711 measured over the range 107 - 1010.7 Pa s showed good agreement with NBS data, with a mean error of 1.2%. The technique was applied to (37AlF3, 12MgF2, 15CaF2, 9SrF2, 12BaF2, 15YF3) and (30.2AlF3, 10.2ZrF4, 3.5MgF2, 20.3CaF2, 13.2SrF2, 10.6BaF2, 8.3YF3, 3.8NaF) (mol %) glasses. No evidence for load-dependent effects was found, and any cessation of penetration was attributable to devitrification during the measurement.

This paper describes the structure of glass melts in the Nb2O5-B2O3-K2O system by high-temperature Raman spectra. Because the authors had adopted a special high- temperature heating apparatus in our experimental work, the Raman spectra of the glass melts can be directly measured in the high-temperature state. The experimental results indicate that the groups of (NbO6)and (NbO4) will replace (BO3) and (BO4) and compose a new structural network by introducing Nb2O5 into boric glass. The (NbO4) belongs to the Td group; it has two IR activity modes and four Raman activity modes. The Nb in the structure is SP3 hybridized orbital and also has one residual electron; it belongs to the (NbO4) and forms a large (pi) bond. Under the influence of the heating field, the (pi) bond is very easy deformed. The Raman matrix element of (NbO4) in the 870 cm-1 is zero, but the dipole transition matrix element is comparatively stable. This shows that the structure skeleton does not collapse. The (NbO6) belongs to the Oh group; it loses Oh group symmetry in the high-temperature state, so the new scattering peaks appear. This research is very useful for the study and production of a new series of optical glasses. Through this work, the structural model of nioboborate glass melts had been established.

The basic properties (light refractive index, density, mechanical strength, etc.) of fused silica are changed by the influence of high-intensity light from the glass transparency region capable of generating excitons by multiphoton absorption. The self-trapped exciton decay near the microcavity in the fused silica structure leads to the stable elementary intrinsic defect pair (nonbridging oxygen atom and three-fold-coordinated silicon atom) generation. At the large- enough light intensities near such a microcavity with a defect, the next exciton can be self- trapped. Then the next elementary defect can appear in the microcavity, and a chemical bond between it and the previously generated defect is formed. In such a way 'the darning' of the microcavity takes place and leads to the increase of the density and the light refractive index in this material. If the opposite elementary defects meet in the microcavity, then the Si-O bond is renewed, whereas if equal defects meet in the microcavity, then weaker 0-0 (peroxy bridges) an Si-Si bonds are formed. Because of this, during the illumination more and more of the above-mentioned weaker chemical bonds appear in the fused silica network leading to the decrease of the mechanical strength of the material.

The mechanisms of photo-inductional change of the alkali-silicate and lead-silicate glasses optical parameters upon exposure to the intense laser radiation with Eg/2 < h(nu) < Eg (Eg is the glass matrix ionization potential) has been studied. It is shown that under these conditions the color centers accumulation and fundamental luminescence are observed owing to two-photon ionization of a glass matrix. The saturation value of additional absorption is dependent on the irradiance of laser radiation. It is defined by the dynamic equilibrium between two-photon absorption and one-photon discoloration of color centers. This effect may be used for bulk holograms recorded in the colored glasses. It was found that the process of two-photon generation of charge carriers affects the increase of absorption in a wide spectral range as well as the change of the refractive index of glass. These effects essentially decrease the brightness of the laser radiation passing through the medium, even for samples less than 1 mm thick. On the basis of the analysis of the characteristics of fundamental and impure luminescence, the kinetics of color centers formation and decay, and the kinetics of refractive index change under conditions of two-photon glass matrix excitation, the available mechanisms of photo-inductional changes of glass optical parameters are offered.

The results of measurements of electrical and optical properties, obtained with the thermally stimulated current and optical absorption methods and luminescence techniques, are presented. The investigated material was the porous glass before and after being impregnated.

Ac and dc conductivity measurements of porous glass samples are performed. The peculiarities of capacitance and conductance vs frequency curves indicate the presence of percolation channels formed by voids with dimensions exceeding the mean values. The data were compared with the results of scanning the porous glass surface with a small-size mercury probe. The observed prenomena are associated with the presence of moisture in the bulk of the investigated samples. It was found practical to expose porous glasses to the toluolum vapors to force out the absorbed water from the microvoids.

Some theoretical problems which may be useful for investigations of glass-composite optical properties are studied. These problems are: estimations of the optical properties limiting values; the effective dielectric function calculations for disordered systems of absorbing particles; coherent Rayleigh-scattering calculations for systems of spherical shells; Mie theory calculations for semiconductor particles with quantum confinement of excitons; Mie-theory calculations of Faraday effect spectra.

Original results and the most interesting aspects of nonlinear spectroscopy in silica optical fibers (OF) are reviewed. The threshold nature of stimulated Raman scattering (SRS) and the shape and intensity of SRS lines was determined. The observed SRS spectra in OF consisted of a number of narrow lines due to silica network vibrations, to dopant and microdefect, and more than 20 overtones and combination vibrations. The anharmonicity constants and the frequencies of harmonic vibrations were calculated for the first time. It was shown that the minimal anharmonicity was characteristic for deformation vibrations of silica tetrahedrons. It was emphasized that the SRS possessed the simple and universal character for express- analytical investigations of type, concentrations, and spatial distributions of dopant and microdefect in any transparent glass media which could be manufactured as OF with optical losses no greater than 100 dB/km.

Ion implantation modifies only the surface layer, so the most informative of the material structures are IR reflectance spectroscopy and AES with ion etching which allow carrying out of direct analysis of elementary composition of an implanted layer. IRS and AES studies have been carried out to investigate Ti+ ion-beam doped silica.

An organically modified silicate (ormosil) material, which contains methyl groups chemically bonded to the silicate network, was developed as a host material for organic dyes. The undoped material is hard, transparent, stable to water, can be cut and polished, and processed at temperatures less than 100 degree(s) C. Absorption and emission spectra are presented for a variety of laser and NLO dyes which were successfully incorporated into the ormosil host material. For comparison, spectra are also presented for some dyes in liquid and/or SiO2 zerogel.

The theoretical basis for nonlinearities in semiconductor and silver quantum dots is outlined. The connection between calculated and measured energies of the quantum levels of CdS in glasses is given. Enhancement of optical spectra of organic dyes is a result of an interaction with silver particles. Applications of glasses doped by quantum dots of CdS or silver particles with organic dyes for photonics and for luminescent solar collectors (LSC) are suggested.

Er3+ doped heavy metal fluoride glasses are studied by use of the upconversion process because they can efficiently convert 800 nm light from a diode laser into visible light. The dynamics of the upconversion processes and the efficiencies of these processes vary with composition and preparation route of the heavy metal fluoride glasses. The dynamics of the upconversion processes in these glasses is discussed, and the dependence on rare-earth concentration, fluoride glass composition, and preparation conditions are discussed. A practical application of this work, the construction of an upconversion laser, is also described.

The upconversion fluorescence properties of Er3+ ions were studied for several glasses in the systems of fluoride, fluorophosphate, and oxide. As an excitation source, the infrared radiation of a GaAlAs laser diode ((lambda) equals 802 nm) was used. A green emission due to 4S3/2-4I15/2 transition could be observed not only for fluoride glasses but also for some oxide glasses composed of heavy metal ions with 30 mW excitation. It was found from the photon sideband spectra that the upconversion intensity was influenced by the energy of phonons coupled with the rare-earth ions and that the energy almost corresponded to the stretching vibration in each glass. The temperature dependence of upconversion intensity was large for the fluoride system, while it was small for the fluorophosphate system. These tendencies could be well explained by considering the temperature dependence of the multiphoton relaxation rate, which is a function of the phonon energy consumed during the nonradiative decay. The results were discussed combined with those of 151Eu-Mossbauer spectroscopy on the local structure and covalency of rare- earth ions in these glasses.

The fabrication of different types of Er3+-doped glasses and the study of their absorption and emission spectra, cross sections, lifetimes, and bandwidths are described. The purpose is to get guidelines for the synthesis of the appropriate glasses to manufacture active planar waveguides. The feasibility of active integrated optical waveguides by ion-exchange on these glasses is also demonstrated, using an Er3--doped soda-lime glass.

Cs+- and K+-exchange in a neodymium-doped soda-silicate glass is investigated. The Nd-concentration is about 4.6(DOT)1020/cm3. K+- exchange generates erfc-profiles with N.A. equals 0.16, whereas Cs+-exchange results in steplike profiles (N.A. equals 0.32). Monomode as well as multimode operation is possible. Stripe waveguides have been formed by thermal K+-exchange using Al- masks with openings from 3 to 10 micrometers . The fluorescence spectrum is not affected by the ion exchange process.

Diode-pumped cw laser oscillations in the 2.7 micrometers region were obtained using 10 mol% ErF3 doped fluorozircoaluminate glass fibers. Lasing threshold proportionately decreased with decreasing fiber core diameter. The minimum threshold observed for 110 micrometers core fiber was approximately 10 mW in absorbed pump power. Maximum slope efficiency of 8% was obtained for 1% output coupling. Output performance was significantly affected by the pump wavelength. The mechanism of cw lasing in this self-terminating system was discussed.

The phosphate neodymium-doped glasses with low nonlinear refractive index coefficient (1(DOT)10-13SGSE) for large aperture lasers, high neodymium-doped (12(DOT)1020cm-3) glasses for miniature lasers, and phosphate glasses doped with two (Yb3+, Er3+) or three (Cr3+, Yb3+, Er3+) activators have been developed in recent years. The developments were based on the systematic study of variation in glass parameters with changes in glass composition. It has been shown in carrying out the study that there are a number of diverse types of spectra for one rare earth activator, such that each type can be obtained for glasses containing different glass formers. For interpretation of rare earth glass spectra, three variants of stochastic structural models were used. High doped neodymium phosphate glasses characterized with the high value of luminescence quantum yield and excellent chemical resistance could be obtained on the basis of ultraphosphate systems.

This study determines the fluorescent characteristics of Cr3+-doped glass ceramics. The precursor glasses in the systems of B2O3-AL2O3-SiO2, MgO-Al2O3-SiO2, Li2O-AL2O3-SiO2 were prepared at 1500- 1600 degree(s)C. According to the theory that 'the basic units of glass state can be considered as complex anions, which have fixed coordinates and short range order' proposed by Qiu Guanming, the glass ceramics were obtained by adjusting the structure slightly at 670- 880 degree(s)C. From DTA, x-ray diffraction, SEM, and spectral measurements, 126 unequivalent chromium (III) sites in the mullite were deduced, which can be characterized as low, intermediate, and high field. The lineshape function of fluorescence was calculated by the single site model and statistical site model. The results have shown that the theoretical lineshape reproduces most of the essential spectral features of glass ceramics very well, and the selective excitation affects the spectral width, peak position, and lineshape.

Dual-core waveguides are proposed and fabricated in a glass substrate using potassium and silver ion-exchange processes. The waveguides are characterized and their properties are compared to those of single-core waveguides. Their application in production of glass- integrated optic devices is discussed. As an example, dual-core waveguides with etched grating are produced and their performance is determined.

Graded-index waveguides in glass have been produced by different ion-exchange processes, and their optical characteristics measured to check the consistency of two numerical methods for a proper modelling of the refractive index profile: the results obtained by the two methods appear to be in quite good agreement in most of the cases. An external reference was provided by direct RBS measurements of the concentration of exchanged ions.

Binary ion exchange is widely used to fabricate passive waveguide components for application in integrated optics. In this paper the authors present a technique for determining the stress in ion-exchanged waveguides; this is accomplished by measuring the phase difference between TM and TE modes of a certain order, excited at the same time in the waveguide by entering it with a light beam linearly polarized at an angle of 45 degree(s) with respect to the stress axes. The phase difference of the two modes due to the stress anisotropy is measured without requiring precise angular settings or absolute intensity measurements. The technique has been checked by analyzing some Ag+-Na+ exchanged waveguides, and particular attention has been paid to the analysis of waveguides prepared by electromigration processes.

The fabrication of single-mode glass waveguides by silver ion exchange with ionic masking has been studied. In this ionic masking process metallic stripes are first patterned to mask the potassium ion exchange. Then the stripes are removed and silver ion exchange is performed. This produces waveguides in the previously masked regions where potassium ions are not present. The study on the efficiency of the ionic mask is presented. Then the measured mode profiles are compared to the calculated mode profiles. Finally, the situation in which potassium ion exchange does not increase the refractive index of the glass is discussed.

Nuclear Techniques, such as Rutherford Backscattering Spectrometry and Nuclear Reaction Analysis , have been extensively used in the near surface analysis of glass. They provide a non destructive analytical method, with high depth resolution and without radiation effects induced by the analyzing beam. In particular we used Nuclear Techniques for the analysis of chemical and physical processes involved in optical guide formation. Optical waveguides were produced by using electromigration from metallic films and a comparison was made with ion-exchange processes. A systematic study of the mechanisms which govern the in-depth migration of Ag, Au and Cu ions in glasses, in the presence of an external field, was performed in orr to create buried waveguides. Metallic films were evaporated on the surface of glasses of different composition. Electric fields, ranging from 300 to 1000V/cm, were applied across the glasses for different times and temperatures. The metal ion distribution and glass composition modifications were analyzed. Theoretical and experimental profiles have been compared and the importance of the different parameters (electric field, glass temperature, metal surface layer thickness, process duration) have been high lighted. The electromigration technique was also applied for the formation of strip waveguides.

A guided-wave Mach-Zehnder interferometer structure, based on the use of a four-port hybrid optical coupler consisting of symmetric and nonsymmetric y-junctions, is proposed for wavelength division multiplexing application. This structure provides low sensitivity to fabrication parameters and optical polarization and can also be applied to wide wavelength spacing operations. Interferometers for wavelength splitting in the 1.3 and 1.55 micrometers windows were designed and fabricated into a glass substrate with a dry silver ion exchange process. The measured crosstalk was -30 dB with nonpolarized light.

The discovery of high-temperature superconductors (HTS) has opened new opportunities for applications of superconductors in optoelectronics. The HTS perovskites represent a new class of solid-state materials, exhibiting many very interesting and potentially useful electronic, optical, and electro- optical properties. They also operate in the 30-80 K temperature range, where refrigeration is cheap and the parameters of semiconducting devices are optical. A review of the substrate materials and deposition techniques suitable for fabrication of high-quality epitaxial HTS films for electronic and optoelectronic applications is given. Laser processing techniques of HTS films are presented, with a special emphasis put on the laser writing method, which enables the definition of superconducting and nonsuperconducting regions in the same, epitaxial HTS film. Two possible approaches for the development of a complete optoelectronic system with the elements based on the HTS films and operational at liquid-nitrogen temperatures are presented. The first approach consists of manufacturing the devices made of conventional electro- optic materials and containing HTS transmission lines and electrodes. Design and properties of ultrafast HTS interconnects are discussed, and a new concept of the Mach-Zehnder-type YBa2Cu3O7-y-on-LiNbO3 optical modulator is introduced. The second, more futuristic approach, is to exploit contrasting properties of the oxygen-poor and oxygen-rich HTS phases to fabricate novel, monolithic devices. Recent experiments, which reveal intriguing optical properties of HTS films, and are most relevant for the development of all-HTS optoelectronic devices are discussed. Several practical devices, such as high-frequency modulators, ultrafast-pulse generators, and sensitive photodetectors will be presented.

The objective of this paper is to motivate a new class of digital logic. OptiComp has focused on a digital optical logic family in order to capitalize on the inherent benefits of optical computing which include: high FAN-IN and FAN-OUT; low power consumption; high noise margin; high algorithmic efficiency using 'smart' interconnects; and free space leverage of GIBP (gate interconnect bandwidth product). Other well known secondary advantages of optical logic include (but are not limited to): zero capacitive loading of signals at a detector; zero cross-talk between signals; zero signal dispersion; and minimal clock skew (a few picoseconds or less in an imaging system). The primary focus of this paper is to demonstrate how each of the five advantages can be used to leverage other logic family performance such as GaAs; the secondary attributes will be discussed only in the context of introducing the DOC III architecture.