This PDF file contains the front matter associated with SPIE Proceedings Volume 6647, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing

Coatings that can self-modulate their optical properties as a function of an external stimulus are of significant technological interest. In this regard, the possibilities for thermo- or electrochromic materials such as VO₂ and WO₃ are already comparatively well-known. Here, however, we explore a new kind of 'smart' coating, based on the active control of a plasmon resonance in nanoparticles. One possible system is based on the modulation of the plasmon resonance of a precious metal nanorod or nanosphere by an active dielectric shell. The active dielectric undergoes an insulator-to-metal transition on increase of temperature which modulates the plasmon resonance of the underlying precious metal nanoparticle, thereby changing the wavelength at which its optical extinction is maximum. In the case of nanorods, the absorption maximum of the longitudinal plasmon is particularly sensitive to the aspect ratio of the nanoparticle and the dielectric properties of the environment, and may be readily tuned across the visible and near-infrared portions of the spectrum. In addition, nanoparticles of certain thermochromic dielectrics, such as VO₂, are expected to have a plasmon resonance of their own which can be switched on or off by control of the temperature. We consider some of the possibilities, using both the discrete dipole approximation and the exact analytical solution due to Mie to calculate the optical properties.

Using a dynamic oblique-angle deposition technique, we have demonstrated the direct formation of Ag nanorods with quasiparallel major axes on a template layer of oxide having a strongly anisotropic surface morphology. The optical properties of the nanorods are tuned by the deposition conditions without any pre- or post-treatment, and the resulting nanocoatings containing the Ag nanorods exhibit high surface-enhanced Raman scattering (SERS) activity. In addition to high uniformity over a large area, our nanocoatings contain a large number of isolated nanorods with a high density. Using the optimum Ag nanorods, SERS imaging of microdroplets of a rhodamine 6G solution has been successfully demonstrated. The space resolution of the imaging is of the order of at least a few μm. These features are quite appropriate for the SERS imaging of biomaterials.

Vanadium dioxide undergoes a reversible metal-insulator phase transition at about 68°C. Coatings of this compound are reflective in the infrared above this temperature, and transmissive or absorptive below it, while resistivity changes by several orders of magnitude. We present a convenient method for depositing films with nano-size grains, which are then optically and electrically characterised. Emphasis in this study is the impact of aluminum doping and grain structure. The optical hysteresis is presented and its switching range is not altered at different doping levels but the value of transition temperature Tc does shift. In contrast hysteresis in dc resistance does change with a strong correlation between the fall in resistance in the semiconductor state with doping, the drop in Tc and the electrical properties in the metal state. For grain sizes under about 180 nm the conductivity in the metal phase is not linear in temperature but is thermally activated, with activation energies ΔE dependent on both grain size G and doping level. Simple mathematical relationships are found connecting ΔE with G and with carrier density in the semiconductor state. ΔE ranges in our samples from 0.15 eV in the smallest grain sizes to around 0.06 eV. This anomalous low frequency metal response is linked to excitations that arise in the metal phase associated with transient singlet pairing on neighbouring sites. Such pairing is weakened by doping, and in large grains appears to be present but incoherent.

We present a novel method of modulating total internal reflection (TIR) from an optical surface using a solution of dye ions in combination with a nanostructured electrode. Previous work using the electrophoretic movement of pigment particles to modulate TIR was limited by agglomeration of the pigment over time. Dye ions do not suffer from this limitation, but because of their small size they have significantly smaller absorption cross-section per unit charge than pigment particles which are generally two orders of magnitude larger. This significantly limits the maximum absorption caused by electrostatic attraction of the ions to a transparent conductive electrode. This can be overcome by using a transparent conductive nanoporous thin film as the electrode in which the porosity increases the effective surface area, allowing more dye ions to move into the evanescent wave region near the nanoporous transparent electrode and thus substantially increases the amount of absorption. In this paper, we demonstrate the modulation of TIR by observing the time-dependent variation of the reflectance as the dye ions are moved into and out of the evanescent wave region. This approach may have applications in reflective displays and active diffractive devices.

This review first describes the present status of research and development of visible light photocatalysts and then application products on the market are introduced. Finally, future trends of technology and market of photocatalysts will be discussed.

Titanium dioxide thin films were formed by electron-beam evaporation onto fused silica substrates using serial bideposition (SBD). The SBD technique combines rapid substrate rotation and oblique-angle physical vapor deposition (PVD) to create optical coatings that are composed of nanostructured columns which exhibit large birefringence values in the plane of the substrate. In this study, post-deposition annealing was used to crystallize amorphous TiO₂ thin films formed by SBD to improve birefringence without significantly increasing optical absorption or scattering. Birefringent thin films were fabricated at deposition angles ranging from 60° to 75° and annealed in air at temperatures ranging from 200°C to 900°C to form anatase and rutile TiO₂. Changes in the optical properties, crystallinity, and nanostructure were characterized by ellipsometry, x-ray diffraction, atomic force microscopy, and scanning electron microscopy. It was found that optical anisotropy increases strongly upon formation of anatase, yielding in-plane birefringence values that doubled from 0.11 to 0.22 in the case of TiO₂ thin films deposited at 60° and annealed at 400°C. Raising the annealing temperature to 900°C to form rutile thin films increased the thin film birefringence further but also led to low optical transparency due to increased absorption and diffuse scattering.

The electrical and optical properties of mesoporous gold are compared to those of thin porous gold films and a simulated thin film made by randomly distributing voids in gold, until the voids fill 76% of film volume. All layers are electrically conducting but in some cases the critical percolation thresholds are close to zero, so conduction is possible at very high void content. Significant qualitative differences are apparent between the properties of mesoporous gold, and very thin sputtered gold containing voids, in plasmonic responses at optical frequencies and in dc resistance, both as a function of fill factor. The mesoporous films have an effective plasma frequency determined by void fill factor and structure, but do not support surface plasmons. In contrast thin porous gold layers display optical features associated with localized and de-localized surface plasmons. Sputtered porous gold is 2-dimensional and its percolation threshold requires a "Swiss-cheese" rather than particle cluster model. Thicker mesoporous layers have critical parameters consistent with very high connectivity, or equivalently large hyper-dimensionality. Our meso-gold samples display various hyper-dimensionalities from 3 to above 10.

We present here a simple method to synthesize organic-dispersible colloids and a scenario for the ultra-fast fabrication of silver/polymer nanocomposite by light-induced crosslinking polymerization. The objective of this work was to apply UV-curing technology for the fabrication of nanocomposite materials containing silver nanoparticles dispersed in a polymer binder. This new route allows processing operations to be simplified and the properties of the final product to be improved. A special attention has been paid to the synthesis and dispersion of metal nanoparticles in various monomers and oligomers and to the photopolymerization kinetics. The silver nanoparticles were generated by reduction of AgNO₃ with t-BuONa activated sodium hydride. Ag(0) particles present a narrow size distribution with an average diameter of 6.5 nm. Transmission electron microscopy (TEM) analysis has shown that Ag(0) nanoparticles are well dispersed in the acrylic resin. The curing process was followed quantitatively by FTIR spectroscopy through the decrease upon UV exposure of the IR bands characteristic of the functional groups. The silver nanoparticles have no detrimental effect on the photopolymerization kinetics. The incorporation of metal nanoparticles was found to greatly reduce the gloss of UV-cured coatings. Moreover, the outstanding optical and viscoelastic properties of these UV-cured nanocomposites opens up interesting perspectives in various fields of applications (optics, nanoelectronic, biology...).

Layer-by-layer electrostatic self-assembly (L-b-L ESA) method was used for the immobilization of biomolecules onto the sensor substrate surface. As opposed to the LB method, L-b-L ESA is independent of the substrate size and topology. In addition, the LB technique typically cannot be used to form films thicker than several monolayers because defects occur and are replicated through the film structure as additional layers are added. Unlike LB schemes, L-b-L ESA processing permits the molecular-level self-healing of defects that may occur in individual monolayers as additional monolayers are gradually added layer by layer to the substrate during the synthesis process. Individual layer thickness is controllable by factors such as concentration, molecular weight, and ionic strength. What's more, the process is performed with water-soluble molecules, which is required for many biological macromolecules. Any solvent-accessible surface is appropriate for the coatings. Last but not the least, in comparison with LB or physical vapor deposition techniques; the instrumentation cost is very low. Experiment results have demonstrated successful immobilization of Oligonucleotide onto fused silica optical fiber tip by means of L-b-L ESA. The method is shown to be fast, simple and cost-efficient. This will provide a viable, simple and fast method for biomolecule immobilization for a large number of various biosensors.

Crystalline TiO2 (Anatase configuration) thin films is widely used in the photocatalysis and photovoltaic industries ((self cleaning surface and renewable energies for example). The synthesis of these films is obtained from a dispersed solution of molecular poorly condensed species using Sol-Gel and liquid deposition processes. It allows the introduction of organic molecules (porogenes) inside inorganic network to create what is called hybrid materials. Spectroscopic ellipsometry is the technique of choice to characterize thickness and refractive indices of such thin layers. The adsorption of water at atmospheric pressure within the pores, modifies the refractive index of the layer. The change in refractive index induced by the introduction of water is measured by ellipsometry. A Lorentz Lorenz effective medium model is used to calculate the volume of water adsorbed by the material. Atmospheric Ellipsometric porosimetry (EPA) measurements become an effective method for characterization of porosity, pore size distribution (PSD), average pore size, Cumulative surface area and Young's modulus of porous films. EP is also suitable to evaluate the sealing of a porous layer.. EP evaluates the change in refractive index due to the penetration of the solvent through the sealing layer into the porous layer. In this paper, the instrument as well as some examples will be presented the abstract two lines below author names and addresses.

Micro and nano-patterning of photopolymer materials was successfully carried out by using near-field irradiation configuration. In particular, Evanescent Waves created by total internal reflection were used to induce the photocrosslinking of an acrylate-based photopolymer sensitive at 514 nm. We demonstrate here that the thickness of the polymer layer can be tuned from few tens of nm to several microns by controlling the irradiation conditions. The sample was characterized by profilometry, Atomic Force Microscopy and spectroscopy. In addition, relief gratings with adjustable fringe spacing were recorded by interferometric method. Effect of photonic parameters on the gratings geometry is discussed. By changing the irradiation conditions, it is possible to easily obtain patterns with different geometries, which emphasizes the high versatility of the process. This study presents high fundamental interest in the frame of nanofabrication since it provides important information on the effects of confinement at a nanoscale of the photopolymerization reaction. Such data are of primary importance in the field of nanolithography since the effect of parameters such as dye content, oxygen quenching, photonic conditions can be evaluated. Moreover, since the choice of the monomer can be done in a wide range of composition, such nanopatterned polymers surfaces present many interests in the field of optical sensors, photonic crystals, optics, biology...

We have demonstrated stable surface-enhanced Raman spectroscopy (SERS) on arrays of Au nanorods aligned on a photocatalytic TiO₂ layer. We used dynamic oblique deposition (DOD) in order to control the morphology of both the Au nanorods and the TiO₂ layer so that both Au and TiO₂ appear on the surface and play the roles of Raman enhancer and self-cleaner, respectively. TiO₂ template layer was formed by depositing Ti₂O₃ onto heated glass substrate in an oxygen atmosphere so that it was ready as photocatalyst when the deposition was over, without post annealing in the air. A serial bideposition technique (SBD) at a deposition angle of 85° was used to control the morphology of TiO₂ layer suitable for the growth of Au nanorods. Then, Au nanorods were arrayed by depositing Au with different deposition angles and thicknesses on the TiO₂ layer. We investigated the photocatalysis and SERS properties of the samples and found that they show both good photocatalysis and strong signals of SERS although these properties varies depend on the deposition angle and thickness of Au layer. Most importantly, we found that the SERS signals measured on our samples have shown spatially-, temporally-stable characters which have not been observed before on the Ag or Au nanorods deposited on a SiO₂ layer. This stability is interpreted in terms of the self-cleaning character due to the photocatalytic TiO2 template layer.

Polycrystalline aluminum nitride films were deposited by reactive radio frequency magnetron sputtering on silicon and molybdenum substrates without substrate heating. Surface and microstructure properties were investigated by atomic force microscopy and x-ray diffraction. X-ray photoelectron spectroscopy was used to study the composition of the surface. Their optical properties were studied by spectroscopic ellipsometry in the 430-850 nm wavelength range and modeling was carried out. The optical properties so obtained were correlated with the AlN films' structure and crystalline quality.