Erbium {tris[bis(trimethylsilyl)]amide} has been employed as a dopant material for incorporation of the rare earth element erbium into a silicon host lattice for fabrication of monochromatic and temperature-independent optoelectronic devices. Electronic characteristics, including room temperature electroluminescence and glancing angle X-ray diffraction, have been obtained from deposited Si:Er films. The utilized erbium amide precursor has been compared to alternative erbium sources as hydrocarbon and fluorocarbon containing (beta) -diketonates (tmhd and fod).

Optical amplification performance is channel waveguides involves the absence of OH groups to have Erbium doping efficiency and a high refractive index variation between the guide and the surround material to have the maximum confining as possible. In this way, we propose a new hybrid material using a hydrophobic silica precursor to reduce the OH content mixed to a diacrylate monomer which reactivity allow a high refractive variation under UV light exposure.

New organic-inorganic sol-gel films have been prepared starting from mixtures of silicon and zirconium alkoxides or pure zirconium alkoxides and deposited on metallic substrates. Coatings loaded with a fluorescent SrF₂:Y²⁺ powder have been deposited on stainless steel rendered adhesive by a special oxidative surface treatment. The final deposits have successfully supported drastic adherence standard tests after several dips into liquid nitrogen, and have been used for temperature dependant fluorescence decay measurement. The fluorescent gels have been coated on a rotating cylinder into liquid nitrogen and the fluorescence decay measurement device is described, as well as the optical device used for the light analysis. Efficient measures can be registered at rotating speeds as fast as 3000 rpm. On the other hand, xerogels issued from pure zirconium propoxide have been functionalized with electroactive ferrocenes bonded to acatylacatone or salicylate moieties. All ferrocenes included into the gels can be electrochemically reversibly oxidized and reduced. Efficient modified electrodes can be built, whose behavior is in perfect accordance with the theoretical prediction in the case of an homogeneous repartition of the redox species inside the film.

A high optical quality Rhodamine 6G doped low melting temperature fluorophosphate glass was obtained. The glass transition temperature, crystallization temperature, melting temperature, refractive index, and chemical durability in the water were examined. The absorption spectra, excitation spectra, and emission spectra of the Rhodamine 6G in the low melting temperature fluorophosphate glasses were investigated. The effect of melting time of Rhodamine 6G in the glass on the spectral properties was investigated. The results indicate that this low melting temperature glass is a promising host for laser dyes. The aggregation and degradation of Rhodamine 6G were significantly diminished in this low melting temperature glass.

We present two techniques to use hybrid sol-gel materials for electron-beam lithography and direct writing of surface relief diffractive elements. We are able to obtain direct physical electron beam etching of hybrid sol-gel glass and variable- doses can induce complex multi-phase-level diffractive elements and apodized sol-gel waveguide gratings. We are also able to obtain hybrid so-gel glass formation under the electron radiation, so that material can be used as a negative resist in electron-beam lithography. Both of these techniques are promising for the fabrication of submicron optical components and micromachining tools such as embossing masters for the replication.

Organic-inorganic hybrid material realized by sol-gel process is a new promising technology for the fabrication of integrated optical circuits. Effective devices are already achieved. Two approaches are studied here to improve the density of integration: crossed and stacked waveguides. Both processes are compatible with our organic-inorganic material. One level devices with crossing waveguides as well as multilevel devices have been studied and made: neither additional insertion loss nor crosstalk have been measured. Theoretical studies show the possibility to fabricate vertical coupler in a multilevel structure by adjusting the buffer layer thickness between guiding layers.

The lightwave communication technology is experiencing tremendous growth in the volume and flow of information. Spectral discrimination filtering, wavelength division multiplexing and dense wavelength division multiplexing are making it possible. The high refractive index modulation and design flexibility of Polyglass material makes it very attractive to produce such devices.

Polyglass thin films produced by a sol-gel process have emerged as the material of choice for production of low-cost glass integrated optics components on silicon. In this paper, we report on production of polyglass waveguides, gratings, star couplers, and dense wavelength division multiplexers for telecommunications, data communications and computer networks applications.

Hybrids organic-inorganic nanocomposites are obtained though the hydrolysis and condensation of diethoxymethylsilane and methyltriethoxysilane alkoxides with or without the use of Lewis acids such as Zr(OPrⁿ)₄ or Al(etac)(OBu^s)₂ precursors. These materials which present both reductive and hydrophobic behavior are performant host matrices for rare-earth cations and for photochromic dyes such as from spirooxazines (SO), diarylethene derivatives (DE) and furylfulgides (FF). We report the room temperature synthesis of new Eu²⁺ doped hybrid materials together with their absorption and emission properties. The photochromic properties of the different dyes (SO, DE, FF) in these hybrid solid matrices are also described. Very fast kinetics of coloration and thermal fading (0.2 s^-1) are reproducibly evaluated for spiroxazines, while for the first time, quantum yields of the coloration process of diarylethene derivatives and furylfulfydes embedded in solid sol-gel derived matrices are measured.

A new synthesis route to organic-inorganic composites with low OH- and CH-content has been developed. Thus methacrylate- modified chlorosilanes were either homocondensed or cocondensed with fluoroalkyl-modified chlorosilanes by a non- hydrolytic reaction with 2-methyl-2-propanol under formation of an inorganic network and hydrogen chloride and tertiary butyl chloride as well. Remaining chlorosilane groups were reacted by a second alcohol treatment to obtain air-stable, highly condensed, and low OH-containing sols. The condensation was followed by ²⁹Si-NMR-spectroscopy, showing T²- content of up to 60% and T³ content of up to 35% for trichlorosilanes and D²-content of more than 90% for dichlorosilanes respectively. The OH-content, which was estimated by FT-IR-spectroscopy, was lower than 10% referring to materials prepared by the conventional aqueous sol-gel process. For further decrease of the CH-content copolymerization with fluorinated methacrylates was investigated. After addition of a photoinitiator transparent bulk materials with a diameter of 1 cm and a length of 1.5 cm were obtained by photopolymerization in closed UV-transparent containers using a Beltron^r UV apparatus with a low pressure Hg-Xe lamp. NIR-absorbance measurements were carried out and optical losses of bulk materials were determined. Cocondensed and copolymerized materials show low optical losses of 0.12 dB/cm at 1300 nm and 0.33 dB/cm at 1550 nm.

We give an account of the use of in situ waveguide Raman spectroscopy to provide vibrational information about structural changes that occur when a hybrid organically modified silicate glass is irradiated with UV or visible photons. The method is useful for 'reading' what transpires in an optical waveguide device as it is being formed by photoinscription methods. We describe a novel method for photoinscribing a circular (d equals 10 micrometer) optical fiber core on a SiO₂-coated Si wafer. This is achieved by photolysis of a visible light photoinitiator in a slab waveguide while a standing wave is established in the film with the 514.5 nm TE₀ mode of an argon ion laser. Simultaneous waveguide Raman spectroscopy (WRS) gave insight into structural changes in the matrix that ensue when the matrix is irradiated. As with UV induced densification, polymerization of the methacrylate groups by photoinitiation with visible light triggers further polycondensation reactions between unconverted equalsVSi-OCH₃ and equalsVSi-OH to tighten the glass matrix.

Dynamic mechanical thermal analysis (DMTA) and UV/VIS spectroscopy were applied to investigate the thermomechanical and optical properties of thermoplastic nanocomposites. The thermoplastic matrix material used was a copolymer derived from methylmethacrylate (MMA) and 2-hydroxyethylmethacrylate (HEMA). To improve the mechanical properties, especially in the high temperature region above the glass transition temperature (T_g) of the matrix, the copolymer was filled with spherical 10 nm silica particles (filler content 2, 5, and 10 vol% respectively). The particles were introduced in the polymer matrix after appropriate surface coating to control the filler dispersion in the matrix and the filler/matrix adhesion. The coating was performed using acetoxypropyltrimethoxysilane (APTS) to achieve higher filler/matrix compatibility compared to unmodified silica particles dispersed in the polymer matrix. Methacryloxypropyltrimethoxysilane (MPTS) was used to improve filler/matrix adhesion by covalent bonding between the filler surface and polymer matrix. The appearance of the poly(MMA-co- HEMA) nanocomposites (denoted:PMH nanocomposites) changes from translucent for the systems containing uncoated silica to more transparent for the compositions containing silane coated silica. This is indicated by a decrease in scattering/absorbance losses from 1.48 dB/cm to 1.06 dB/cm at (lambda) equals 650 nm. Investigations of the morphology of the same nanocomposites using transmission electron microscopy (TEM) showed that by coating the particles with silane an almost perfect dispersion of the fillers in the matrix can be realized. The more homogeneous dispersion of the silane coated particles in the polymer matrix compared to the uncoated silica is responsible for the increase in transparency of the systems. However, the composition dependence of the refractive index is in accordance with the expected behavior and shows a decrease with increasing amounts of silica (0% silica: n_e equals 1.5085, 10% silica n_e equals 1.4965) whereas, the Abbe number remains almost constant at v_e equals 58 for all compositions. In addition, the fortyfold increase in the value for the storage modulus E' at T equals 170 degrees Celsius [derived from dynamic mechanical thermal analysis (DMTA)] for the system with 9.5 vol.% MPTS coated particles compared to the unfilled matrix indicates an increased thermomechanical stability of the nanocomposites.

Multifunctional organic-inorganic nanocomposites are of considerable interest in photonics, optoelectronics, and biophotonics. This paper will focus on two topics. In the first part of the paper, we will focus on semiconductor nanocluster sensitized photoconductivity and photorefractivity. The results of photorefractivity studies in newly developed polymer composite PVK: TCP: CdS: NPP are presented. The composite contains charge transporting polymeric matrix of poly [N-vinylcarbazole] (PVK), thiocresol capped CdS photosensitizing nanoclusters, and second-order nonlinear optically active chromophore N-(4- nitrophenyl)-L-prolinol (NPP). Efficient plasticization of the host polymeric matrix was achieved with tricresyl phosphate (TCP). The electro-optic modulation, degenerate four-wave mixing (DFWM) diffraction efficiency and two-beam coupling properties of photorefraction were studied. In the second part of the paper, we investigate surface enhanced fluorescence in a silica matrix using dye in close association with silver nanoclusters. To optimize the photonic functions of 4-[N- (2-hydroxyethyl)-N-(methyl) amino phenyl]-4'-(6- hydroxyhexyl sulfonyl) stilbene (APSS) we have utilized the concept of plasmon enhancement, where resonance interaction with nanosize metal clusters enhances the various optical properties. Novel sol-gel processing has produced composites containing APSS and silver nanoclusters. The energy transfer between the plasmon resonance of the silver nanocluster and the excited state of APSS has been demonstrated.

Good optical quality, thin films have been prepared from ormosils based on equimolar tetramethoxysilane (TMOS) and trimethoxysilylpropylmethacrylate (TMSPM) by a single dip coating onto silica substrates then gelling and drying the film below 100 degrees Celsius. Zirconium tetra-n-propoxide (Zr), complexed with methylacrylic acid (MA), was added to the base ormosil TMOS.TMSPM to raise the film refractive index above that of the silica substrate to effect waveguiding. Refractive index dispersion in the visible was measured for bulk specimens of the base composition using the Abbe refractometer. Refractive index and film thickness of the ormosil slab waveguides were determined using the method of prism coupling of a HeNe beam (wavelength 632.8 nm) by measurement of the angular displacement of the emerging modes. Film thickness was also measured using a Dektak 3030T profilometer and confirmed to be about 3 micrometer. Increasing the atomic fraction [Zr/(Si + Zr)] from zero to 0.296 led to a rise in waveguide core refractive index from 1.4768 (assumed the same as bulk specimen) to 1.52218. Higher additions of Zr led to cracking of the films.

We report on fabrication of ridge waveguides in UV-light sensitive glass sol-gel thin films, deposited on silicon substrate, using a simple photolithography process. The single-layer films are prepared at low temperature and deep UV-light (DUV) is employed to make the waveguides. The effect of fabrication parameters on waveguide shape is investigated.

The synthesis of transparent nanomers by the incorporation of nanoscaled tantalum oxide into an organic-inorganic composite matrix and their subsequent characterization are presented. The matrix materials used consist of a mixture of organically functionalized silanes and polymerizable monomers. The mixture does not exhibit phase separation, even down to the lowest nanometer scale, as revealed by SAXS measurements. The addition of nanoscaled Ta₂O₅ particles (mean particle diameter: 4 nm as determined by photon correlation spectroscopy) aims to increase the refractive index of the nanomers. The preparation of the oxide sol and the optimization of the synthesis with respect to compatibility with the matrix material, thereby avoiding agglomeration effects, is described. After incorporation of the particles in the monomer mixture, a photopolymerization step, followed by curing with a temperature program up to 90 degrees Celsius, led to colorless and transparent monoliths. The volume shrinkage, caused by polymerization, decreases from 8.2% for the unfilled matrix material to 5.8% for a nanomer containing 30 wt.% tantalum oxide. The shrinkage decreases linearly with increasing filler content of tantalum oxide. The increase in refractive index is about 7.4 X 10^-4 per wt.% oxide (measured at a wavelength of 546.1 nm). The coloration of the monoliths is expressed as yellowness index G according to DIN 6167. Color values attained for nanometers with up to 15 wt.% tantalum oxide are comparable to values for commercial optical polymer materials. Nanomers containing 15 wt.% tantalum oxide show transparency losses at a wavelength of 850 nm below 0.1 dB/cm.

Some examples of ordering in thin inorganic nanocrystalline films, structure of dye-sensitized thin films on optically transparent nanocrystalline electrodes, inorganic epitaxial growth and first heterosupermolecules with nanoparticles as coordination center are accumulated in this short review of our results and literary data to discuss the questions of morphology and optoelectronic properties of nanocrystalline junctions in resulted assembled structures.

We have prepared a hybrid organic-inorganic glass composite incorporating an aminosulfone dye via the sol-gel process. The dye was functionalized with alkoxysilane moieties to anchor it covalently into the silicate network. Co-condensation with the organically modified silicon alkoxide methyltrimethoxysilane (MTMS), gave transparent high-quality films that could be deposited up to 10 microns thick in one step. We discuss the structure and second-order nonlinear properties of these materials. For a poled and cured sample containing 0.5% (w/w) of the NLO dye, the magnitude of the electro-optic coefficient r₁₃ is 2.2 plus or minus 0.4 pm/V.

This paper reviews two emerging approaches towards new materials and related device technologies for nonlinear photonic applications. Hybrid organic-inorganic sol-gel materials are shown to be meeting material engineering requirements, with the electrically poling of Disperse Red1- like chromophores grafted to a syloxane chain exhibiting a remarkably high non resonant second-order nonlinearity together with long-term orientational stability. Furthermore, an all-optical poling method based on the photoinduced orientation of molecules in various matrices, appears as an appealing alternative to the traditional electric field poling, capable to circumvent its intrinsic limitations such as the necessity of a dipolar chromophore. We have experimentally demonstrated the possibility to implement a macroscopic multipolar organizational scheme by way of purely optical photoinduced processes. Adequate choice of the polarization states of fundamental and harmonic <<write>> beams will leave a permanent imprint of any desired symmetry pattern onto the (non)linear material.

We optically functionalized transparent hybrid matrices prepared by the sol-gel process by doping them with organic chromophores. Highly dense and chemically stable bulk and film materials of good optical quality have been synthesized in this way. Such materials can exhibit very different optical properties, depending on the choice of the chromophores and the type of environment provided by the sol-gel matrices. On one hand, the optical properties conferred to the solid state material can be those for which the dyes have been known and optimized in solution; this is, for example, the case of solid state dye lasers which performances have dramatically improved over the past few years, from the possibility of emitting 1,000s of microjoules pulses to 1,000,000s of millijoule pulses, illustrating the huge optimization potential of this material synthesis route strong reverse saturable absorption for optical limiting applications. . . On another hand, new properties can be demonstrated in the solid form, in particular, due to the restricted motion of the dopants in rotation and translation; that is the case of all optical memory, of second order nonlinear activity ((chi) ⁽²)), and, most recently, photorefractivity. We will especially detail the photorefractive properties of new media based on hybrid organic-inorganic materials containing charge transporting molecules and second order nonlinear optical chromophores introduced as side-chain units. These materials, prepared by the sol-gel process in the form of few micrometers thick films, were studied by two beam coupling (2BC), electronic absorption, electro-optic and photoconductivity experiments. The presence of a strong static electric field (30 V/micrometers ) inside poled films was evidenced, and can explain the photorefractive properties obtained without applying any external electric field. Finally, one common issue all organic-based materials have to solve to take advantage of their high efficiencies and have potential applications outside the laboratories, is the chromophore photodegradation which limits the operational lifetimes of devices made from such materials. This point is under investigation and initial results show that the quantum efficiencies of these photoinduced chemical reaction can vary by several orders of magnitude, within this class of hybrid materials.

Ultrafast dynamics of transient photobleaching and recovery of cadmium sulphide (CdS) nanoparticles of different size ranging from less than 3.5 nm to greater than 5.0 nm, dispersed in Nafion films, in self-assembled films, and in aqueous solutions were studied upon excitation at 400 nm with a femtosecond laser. All samples gave transient bleaching in less than 1 ps and a multi-exponential recovery in the wavelength region above about 410 nm. The peak wavelength of the transient bleaching and its time dependence together with the recovery behavior were affected by the particle size, surface treatment and the supporting medium. The peak of the transient bleaching spectrum of larger CdS nanoparticles showed a red-shift during the recovery process, while for the smaller particles no such change was observed. CdS nanoparticles in self-assembled films showed an extremely long-lived bleaching recovery process. Fluorescence-activated CdS nanoparticles in aqueous solutions, which showed very strong and sharp fluorescence near the exciton absorption, showed very fast recovery. These results were explained by the decay of excitons and the recombination of surface trapped electron-hole pairs with different energies depending on the particle size.

Starting from a simple physical model, we propose a new scheme for increasing the fast nonlinear refractive response while decreasing linear and nonlinear absorptions in classical push- pull molecules. This effect is due to the reduction of their donor group strength of classical push-pull molecules. It is confirmed by multi-channel Z-scan measurements and by semi- empirical computations as well. Then, we have functionalized a copolymer, poly(maleic anhydride-co-octadecene), with these chromophores and measured its nonlinear refraction and absorption with respect to the chromophore nature.

This paper describes a method to passively align optical fibers with on-chip ormosil waveguide devices. One objective is to demonstrate that photosensitive sol-gel (ormosil) materials can be applied to fabricate a family of low-cost, high-quality, self-aligned microchip couplers. Feasibility of forming sol-gel waveguide couplers on silicon chips with on- chip V-grooves for passive alignment of ribbon fibers is studied. The optical waveguide material is deposited onto silicon wafers on which high precision alignment grooves are fabricated to support the input or output optical fibers. By forming V-grooves and wave-guides on the same substrate with precise dimensional control, passive optical alignment can be achieved. This passive alignment scheme can result in a large cost reduction for integrated optics' devices. Several cost- and labor-intensive manufacturing processes would be either eliminated or simplified. This scheme can be used for both single- and multi-mode applications. The method is particularly useful for interconnecting on-chip waveguiding devices with optical fiber ribbons, in which multi-fiber alignment is difficult by conventional active methods.