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This paper describes the properties of some new organic-inorganic photochromic layers. They are based on a hybrid organic-inorganic matrix in which tungsten heteropolyoxometallates (SiW12O404-, PW12O403-) are entrapped in a network obtained from the reaction of 3-glycidoxy-propyltrimethoxysilane. The high homogeneity of these materials on the nanoscale leads to transparent monoliths and layers of controlled thicknesses up to 40 µm. The optical properties of the blend are emphasised and the construction of amplitude gratings in the materials by two-wave-mixing experiments is described. The results of the optical experiments and the comparison with the theoretical background are used as a model for photochromic holographic storage processes.

Two different techniques have been used to follow the gelation of photochromic organic-inorganic nanocomposites. The variations of molecular and macromolecular motions in these complex systems have been analyzed. Photo-correlation spectroscopy probes the formation of the gel network. Forced Rayleigh scattering experiences the microstructure of the mixtures via the measurement of the translational diffusion coefficient of entrapped photoreactive targets. In the different mixtures, a drop of the network mobility could be observed around the sol to gel conversion, while the entrapped molecules do not experience the macroscopic transition.

Microlenses made of hybrid organic-inorganic materials have been fabricated on glass substrates using a commercial drop-on-demand ink-jet printing system with a 50 µm diameter nozzle driven by a piezoelectric device. After deposition the drops have been polymerized by UV light irradiation. Viscosity, solvent evaporation, drop-substrate wetting condition and drop and substrate temperatures are the main parameters which govern the production of reproducible lens shapes. The shape and surface roughness of the lenses have been characterized by atomic force microscopy and profilometry. Their optical properties have been determined by light microscopy and spectrophotometric techniques. The printing technique can produce plano-convex spherical microlenses with diameters varying from 50 to 300 µm, focal lengths from 70 µm to 3 mm and f-numbers as low as 0.6.

In der vorliegenden Arbeit wird die Herstellung und Charakterisierung von Relief- und Phasenhologrammen aus C=C-funktionalisierten ZrO2-Nanopartikel gefüllter organischanorganischen Matrix Methacryloxypropyltrimethoxysilan-MPTS/Tetraethylenglykoldimethhacrylat- TEGDMA) beschrieben. Im Ersten Teil der Arbeit wurden Reliefhologramme durch Zweiwellenmischverfahren beschrieben und durch Auswaschprozess des unpolymerisierten Materials entwickelt. Dabei entstehen Reliefhologramme mit Beugungswirkungsgrad von 36.3% und Signal/Rausch =136. Der experimentelle Beugungswirkungsgrad ist höher als der theoretische. Dies wurde verursacht durch zwei Effekte: zuerst wurde das Gitterprofil durch Steuerung der Belichtung quasi viereckig und zum zweiten wurde eine Brechwertmodulation in Phasen mit dem Reliefgitter durch Diffusion von funktionalisierten Nanopartikeln und durch anorganische Vernetzung erzeugt. Für die Anwendungen, wie z.B. Masterherstellung, stellt das Signal/Rausch-Verhältnis eine wichtige Eigenschaft der holographischen Komponenten dar. Um die Oberflächenqualität der holographischen Strukturen zu verbessern, wurden Reliefhologramme durch einen Fixierungsprozess hergestellt. Diese Methode zur Herstellung von Reliefhologrammen ermöglicht ein Signal/Rausch-Verhältnis von ca. 350 und einen Beugungswirkungsgrad nahe dem theoretischen Wert. Weiterhin wurden holographische Relieffresnellinsen durch den Mach-Zehnder-Interferometer und den Fixierungsprozess mit einem Beugungswirkungsgrad der ersten Ordnung von 32 % hergestellt. Ein Weiterer Schwerpunkt des ersten Teils war die Herstellung von Volumenphasenhologrammen durch lichtinduzierte Diffusion von funktionalisierten Nanopartikeln. Die Grundlagen und die Herstellung von Hologrammen durch hochbrechende Nanopartikel mit photopolymerisierbaren Liganden, die im Gradienten chemischer Potentiale bewegt werden können, wurden in dieser Arbeit durchgeführt. Nanokomposite auf organisch-anorganischer Basis in Verbindung mit C=C-funktionalisierten ZrO2-Nanoteilchen wurden aufgrund ihrer optischen Strukturierbarkeit erfolgreich zur Herstellung von Volumen-Phasen-Gittern eingesetzt. Mit ZrO2-haltigen Nanomeren® konnten Volumenphasenhologramme mit Δn = 0.021 bei einer mittleren Brechzahl von 1.51 durch Phasenseparation realisiert werden. Dabei lag die Dicke des Gitters zwischen 1 μm und 16 μm bei einer Gitterperiode von 1,5 μm. Die Vorteile der Phasenseparation gegenüber dem Colburn-Heines-Effekt bestehen darin, dass die Energie für den Hologramm- Schreibeprozess sehr gering ist und eine hohe Modulation der Konzentration der Nanoteilchen durch das chemische Potential erreicht werden kann. Der zweite Teil dieser Arbeit beschäftigt sich mit der Optimierung oder neuen Konzeption der optischen Methode zur Herstellung und Charakterisierung von Hologrammen, wie der Mach-Zender-Interferometer zur Herstellung von Fresnellinsen, die Untersuchung der Brechwertmodulation eines Reliefhologramms, sowie die Schrumpfungs-Messmethode einer photopolymerisierbaren Schicht. Aus dieser Arbeit kristallisierte sich heraus, dass die photopolymerisierbaren Nanokomposite der Nanomer®-Klasse Eigenschaften wie hohe Brechwertmodulation, hohe mechanische, chemische und witterungsresistente bzw. hohe holographische Empfindlichkeit aufweisen. Der Vergleich zwischen den Eigenschaften von organischen Photopolymeren und dem in dieser Arbeit entwickelten holographischen Nanomer®-Material zeigt, dass die Nanomere® ein konkurrenzloses Material für die zukünftigen Anwendungen in der integrierten Optik sind. The aim oft this work was the development and characterization of holographic optical elements. For this propose, this interdisciplinary research work has linked the syntheses of the holographic material and the development of the optical technique solutions to write and to read the optical properties of the holograms. The sol-gel process allows the production of metal oxide particles in the presence of organo alkoxysilanes, bearing various functions. The synthesis of multifunctional transparent organic-inorganic composites is possible, if the particle size can be kept in the lower nanometer range. Composites with a high refractive index generally require the incorporation of inorganic components. The material system used in this work is based on 3-methacryloxypropyl trimethoxysilane (MPTS)/tetra ethylenglykol dimethacrylat (TEGDMA) and zirconium propylate (Zr), chelated by methacrylic acid (MA) has shown to be suitable for index matching, by varying the Zr/MAconcentration. In the first part of this study relief holograms by two-wave-mixing technique have been written and developed using a mixture of solvents. If a local irradiation of the sample with an interference pattern and a periodic modulation of polymerization occur, both the index of refraction (n) and Thickness (d) of the film will change with the same periodicity. The unpolymerised material can be dissolved and a surface relief grating with 36,3% of diffraction efficiency and 136 of signal/noise is obtained. The experimental diffraction efficiency exceed the theoretical value, this effect can be explained by the right angle of the grating relief profile, as well by the volume hologram formed with the same periodicity and phase as the relief structure. To increase the signal/noise-ratio it is necessary to avoid the chemical development step. The relief of micro structures of organic polymer disappears mostly after a full irradiation with UV-light, but the relief micro structures of Nanomer® based material can be fixed by photochemical other oven treatment. Appropriate phase gratings could be formed by 3-dimensional relief structures without any wet chemical development step. Since the wet chemical development step is not required for Nanomers®, very smooth sinusoidal amplitude modulations could be obtained, leading to extremely high signal to noise ratios of up to 350 which is three times better than for organic photopolymers. Beside this the main advantages of Nanomers® compared to state-of-the art polymers or dichromatic gelatins for holography are: − glass-like mechanical stability − very high chemical durability − high UV and long term stability. Fresnel lenses with high quality have been performed using a Mach-Zehnder-Interferometer to write its UV-interference pattern in an organic-inorganic Nanokomposit. Lenses with a diffraction efficiency of the first order of 32 % have been obtained. Another import development step of the first part of this work is the study of the light induced diffusion of functionalized Nanoparticles. The question arises how far C=C-double bonds attached to inorganic high refractive index nanoparticles in a low viscosity polymerisable matrix are able to migrate into the irradiated area. In this case after full area irradiation differences in the refractive index n between pre irradiated areas and the areas being exposed only to the full area treatment should exist. This would lead to a permanent refractive index gradient in the films. Volume phase holograms with Δn = 0.021 by a material refractive index of 1.51 with grating periodicity of 1, 5 μm in a film with 1 μm to 20 μm of thickness have been produced. The second part of this work is focused on the optimization or development of new conceptions of optical techniques to produce or characterize holographic micro structured Elements. The Mach-Zehnder Interferometer has been used to write micro Fresnel lenses and to measure the shrinkage in real time of photopolymerisable coatings. For the refractive index change measurements of relief structure a new concept based on the coupled wave theory and refractive index change of 10-4 can be detected. The comparison with organic photopolymers leads to the conclusion that Nanomers® combines several important technical and technological advantages for UV-holography to be applied on the integrated optic.

A new approach to effective radial gradient refractive index (GRIN) lenses has been developed. It is based on the electrophoresis of ZrO2 nanoparticles with surface charges (ζ-potential) in a solvent free organic-inorganic hybrid matrix, synthesized from dodecandioldimethacrylate (DDDMA), methacryl silane (MPTS) and a complex of zirconium n-propylate (ZR) with methacrylic acid (MA). A DC-electric field of 2000 V/cm is applied by a set of ring electrodes on top and bottom of a cylindrical mould containing the matrix sol. The refractive index profile is measured in situ as a function of time by interferometry. The refractive index profile can be conserved by photopolymerization of the matrix. The resulting refractive index profiles are calculated by computer simulation based on electrophoretical diffusion theory and they are measured by real time Mach-Zehnder Interferometry. The parabolic refractive index gradient of the lenses obtained by variation of concentration of ZrO2 is in very good agreement with the result of computer simulation. By this method, it is possible to obtain 1 cm radial GRIN lenses with a Δn = 0.07 within 5 h.

Nanoparticles produced by a microemulsion for a controlled growth precipitation technique (ZrO2, AlOOH) have been surface modified and incorporated into inorganic/organic composite matrices made from epoxy or methacryloxy silanes. For this reason, the nanopowders have been surface modified with carboxylic acids in order to obtain full dispersibility necessary for high optical quality coatings. ZrO2 was used for obtaining high refractive index coatings. By adjusting an appropriate zeta-potential the particles in a not fully cross-linked matrix have been upconcentrated electrophoretically to obtain graded index optical lenses. Methacryloxy grouping containing particles have been used for the preparation of UV curable hard coatings containing particles have been used for the preparation of UV curable hard coatings containing AlOOH. siO2 and TiO2 particles allow the fabrication of antireflective hard coatings on plastic surfaces by UV curing methods.

A new synthesis and processing route for preparing multilayer interference coatings on plastic substrates has been developed. For this purpose, alcoholic sols of surface modified (3-glycidoxypropyltrimethoxysilane, GPTS) SiO2 and TiO2 particles with sizes of 10 and 4 nm, respectively, were synthesized. Layers were prepared by dip coating, subsequent UV curing (2.1 J/cm(2)) acid thermal post treatment at 80 degrees C for 15 min. Refractive indices of n(D) = 1.47 for SiO2 layers and n(D) = 1.93 for TiO2 were measured. As an example, plastic sheets were coated by angle dependent dip coating with withdrawal speeds from 3 up to 6 mm/s and sin inclination angle of 4 degrees. By this way, one side of the substrate was coated with six quarterwave thick layers (peak wavelength at 750 nm), producing a reflective interference filter with a reflectivity of 72% between 650 and 900 nm. On the other side of the substrate, an interference filter with a reflectivity of 66% between 800 and 1100 nm was produced simultaneously. The interference coatings do nor show delamination or defects after boiling water test (H2O + 5 wt.% NaCl, 8 h) and excellent adhesion (GT 0, TT 1) was obtained in the cross cut tape test. Yellowing did not occur (Delta(g) < 3) and the mechanical properties of the interference filters were not altered after dry sun test at 760 W/m(2) for 270 h. For mechanical protection a nanocomposite hardcoat can be applied on top of the NIR reflectance filters without changing the optical properties remarkably.

A new preparation route for an dielectric NIR-reflexion filter on glass is described. Coating sols are synthesized from SiO2 and TiO2 nanoparticles with photopolymerizable surface ligands. A 5-layer stack consisting of 2 SiO2 and 3 TiO2 layers was deposited on float glass by angle-dependent dip-coating (ADDC) with a fixed angle of 4° to the vertical and subsequent UV-curing. Finally, the whole stack was densified at 450 °C without cracking or discolouring. UV-vis-NIR transmittance and reflectance spectra show a steep increase of reflectance at 750 nm. In the range between 800 nm and 1200 nm, the reflectance is >80%. The visible transmittance is about 72% due to single reflexion peaks. The bandwidth of the NIR reflection filter prepared by ADDC is about 200 nm larger and its maximum reflectance is only 5% smaller compared to vertical dip-coating. The interference layer stack shows excellent stability in Taber Abraser, rubber, saline and UV tests, indicating a high potential for practical application.

A new technique to produce a radial gradient in the refractive index (r-GRIN) in organic-inorganic nanocomposite materials using sol-gel techniques in combination with etectrophoretically induced concentration profiles of oxide nanoparticles is presented. The composite material is based on methacryloxylpropyl trimethoxysilane (MPTS), zirconium n-propoxide (ZR), Methacrylic acid (MA) and tetraethyleneglycol dimethacrylate (TEGDMA). Irgacure 184 was used as a photosensitive initiator. The surface of these particles is enriched with MA which is linked by a chelating complex to the initial ZR component. The TEGDMA component is used to introduce more flexibility in the organic inorganic network and to reduce polymerization stresses. Electric charges on the ZrO2 nanoparticle surface force the particles to diffuse in the gel state by electric fields employed by appropriate electrodes in presence of an electric field. The movement and interdiffusion of the Zr-nanoparticles in the matrix were measured by zeta-potential measurements and by photon-correlation spectroscopy (PCS). In the performed experiments, a radial electric field amplitude of 200 V/cm was used and held for 5 hours keeping the material in the gel state. The variation of refractive index in real time was measured by Mach-Zehnder interferometry. After the electrophoretic process, a polymerization step was carried out to immobilize the An gradient. An was measured by ellipsometry and the value of 0.07 was obtained for a sample of 1 cm in diameter. The form of the concentration profile and hence from the index profile was detected by EDX (Energy Dispersive X-ray analysis) measurements.

Multi-layer interference filters of surface modified SiO2- and TiO2- nanoparticles have been produced on Polycarbonat (PC) and on scratch resistant film. AR-coatings (Anti-Reflex-coatings) were prepared from a dispersion of SiO2 and TiO2 colloidal nanoparticles in a hybrid inorganic organic matrix. The TiO2 particles have been synthesized by addition of HCl and H2O to a solution of titanium tetraisopropanolate in isopropanol. The SiO2 nanoparticles were synthesized by base catalyzed hydrolyses and condensation of tetraethoxysilane (TEOS) mixed with an aqueous solvent. The surface modification of the TiO2 and SiO2 nanoparticles with 3-glycidoxypropyltrimethoxysilane (GPTS) avoids the agglomeration of the nanoparticles and covalent bonds between the matrix and nanoparticles are formed during a photopolymerization step. The nanoparticles were dispersed in a hydrolyzed GPTS matrix and UVI Cygacure 6974 was added as a photoinitiator. The λ/4 (λ = 550 nm) films of TiO2 and SiO2 sols were prepared on PC and on scratch resistant coated PC by spin-coating techniques. The refractive index of the SiO2/TiO2-coatings can be adjusted from 1.47 up to 1.94 depending on the SiO2 or TiO2 concentration. By the combination of index matching and photopolymerization, a low temperature interference filter can be realized for plastic substrates with reflection of 0.5 % at 550 nm. The coatings show excellent adhesion to the substrates in the cross hatch test and promising mechanical properties.

For the preparation of inorganic-organic hybrid materials, synthesis processes have been developed to fabricate so-called hybrid sols, which contain an inorganic core (ceramic or glass) with nano-scale dimensions surface modified by organic groupings. These groupings have been reacted to the particle surface either by amino functional silanes (e.g. in case of iron oxide nanoparticles for amino group containing silanes) reacting with aliphatic acids to make surfaces ureactive and reduce the particle-to-particle interaction by acids, or silanes with polymerizable groupings reacted with organic monomers. In the paper a summary of the recent work and the development of structural models is given. Moreover, it could be shown that surface charges can be generated in the particles within already gelled systems and thus, particles can be tranported by electric fields toform gradient index materials.

New photopolymers have contributed siginficantly to the recent growth of holographic and lithographic applications. Photopolymerizable organic-inorganic hybrid materials, based on methacrylate functionalized silane and zirconia particles as holographic recording material, are presented. Thick films of this composite system were prepared and volume diffractive gratings were fabricated by a two laser beam interference technique. The formation of the gratings is based on the diffusion of high refrractive index components (ZRO2-nanoparticles) to areas with high irradiation intensity with subsequent immobilization by full irradiation of the film. The influence of the zirconia particles as the main component for obtaining highly efficient gratings is presented and the correlation between particle concentration and refractive index profile is shown.

Organic-inorganic composite materials have been used to fabricate refractive microlenses by embossing. A processing technique to produce master microlens arrays is presented. Rheological and mechanical properties of organic-inorganic composite material are adjusted to replicate this master in the material. The patterns are stabilized after embossing by polymerization of the organic groupings using either thermal or photo initiation. Microlens arrays of 10 x 10 lenses were produced and characterized by profilometric measurements as well as optically.

Micro Fresnel lenses were prepared from photosensitive organic-inorganic nanocomposites of the Ormocer-type by irradiation of films of 10 µm in thickness with an interference pattern of two laser beams, mixing a planar reference wavefront and a spherical object wavefront. To monitor the polymerization behavior of the organic groups during irradiation under real time conditions, a characterization method was developed to study changes in optical thickness n d by measuring changes of index of refraction and shrinkage during polymerization. Three-dimensional Fresnel structures were obtained by removing the unpolymerized areas by a solvent. Variation of index of refraction can also be obtained by diffusion of monomers in regions of higher light intensity. A model, similar to the Colburn-Haines model is presented.

A composite material based on organically modified Si alkoxides and modified alkoxides from Zr were prepared. The index of refraction of the system was tailored by the variation of the modified Zr component. Channel waveguides were prepared by a laserwriting technique based on the ability to photopolymerize this material. To decrease optical loss caused by effects of the waveguide surface and to be independent of the used substrate, a buffer layer and a protective layer of the same material of lower index of refraction was combined with a waveguiding film and optical losses were determined.

A sol-gel derived photochromic glass coating of about 1.5 µm in thickness is synthesized by infiltration of Ag+ into a predried Na-Al-B-Si gel layer. The formation of small Ag colloids is initiated by a soft heat treatment and the colloids are converted by a HCl vapour treatment into AgCl crystallites of about 40 nm in diameter. The coating darkens by UV irradiation, forming Ag crystallites of about 5 nm in size. This process is completely reversible at 400°C and no decay is observed in numerous cycles. An amplitude hologram which acts as a diffraction grating with a grating period of about 10 µm can be produced within this layer by a two-wave mixing experiment with laser light of 351 nm wavelength. The diffraction efficiency of this grating is determined to 0.11 %. After thermal erasing the diffraction pattern can be rewritten and erased repeatedly without any loss of efficiency.