Nano-optical devices are raising more and more interest for a variety of applications. From single molecule detection at high molecular concentration by Fluorescence Correlation Spectroscopy (FCS) through optical multiplexing with photonic crystal structures into the exciting field of negative index of refraction materials, the hardware functional dimensions and surely the tolerances are reaching the lower tens of nanometer range. The fabrication of such devices, i.e. the machining of optically interesting materials and material combinations (dielectric, semiconducting, or metallic) at this scale needs adaptation of classical nanostructuring technologies like Electron Beam Lithography (EBL), or the application of serial direct machining technologies like Focused Charged Particle Beam Etching or Deposition with electrons or Ga ions. For low excitation volume FCS measurements, EBL is used for production of high quality nanoscale sub-wavelength apertures in optically opaque (150 nm thick) metal films. The process consists in high aspect ratio patterning of a thick negative e-beam resist film followed by metal lift off. The optically transparent substrate allows the production of any 2D aperture geometry. Difficulties of the production process and their limits are presented. Direct serial machining with charged particle beams shows excellent flexibility and is an interesting 3D alternative method. Deposition by decomposing volatile chemicals under an ion/electron probe, which can be as small as 7nm/1nm, this technique allows for rapid, local prototyping of 2D and 3D nano-structures with highest lateral and axial resolution. The deposited material can be tuned to homogeneous, nanocomposite or crystalline, metallic or transparent, opening the way to applications in photonic crystals and plasmonics. An original in-situ micro-reflectometry method permits the real time control of the growth of the deposits.

Advances in a wide variety of nanotechnologies are expected to substantially benefit future military weapon systems. The technology development cycle for military platforms requires a given technology to reach a defined state of maturity before its use in a deployable system. Nanotechnologies such as quantum dots and carbon nanotubes, while showing great promise of performance benefits, are still considered too immature for immediate use. Defense contractors are in active research of applications of nanoscale engineered materials and devices and are beginning to engage nanotechnology suppliers for future military platforms.

A new concept of in-situ cleaning of fiber-optic connector is proposed, based on nanotechnology. This new nano-brush concept is based on Gecko-lizard foot hairs analogy.

Single crystalline organic nanoaggregates from organic semiconductors such as para-hexaphenyl and sexithiophene might become building blocks for a new type of organic electronic and optoelectronic devices. For the performance of such devices detailed knowledge about the mechanisms responsible for formation and for alignment of the aggregates on the growth substrate is important. On muscovite mica long, mutually parallel fibers of para-hexaphenyl grow, whereas on alkali halides mainly two different orientations, on phlogopite mica three different orientations exist. For sexithiophene on muscovite mica depending on the growth temperature either three equivalent aggregate orientations exist, or a single one dominates. The interplay between epitaxy and dipole assisted alignment on different growth substrates favors either unidirectional or multidirectional growth.

In this study, SiO₂/Al₂O₃/Er₂O₃ (SAE) nanopowders were fabricated by the Combustion Flame − Chemical Vapor Condensation (CF-CVC) technique with average primary particle sizes ranging from 10-30 nm. Fluorescence and lifetime measurements were made both on as-prepared powders, as well as heat treated powders, to compare the thermal annealing effects on optical properties. At an annealing temperature of 1000°C, the SAE became partially devitrified with extremely broad (FWHM ≈ 78 nm) and flat emission spectra, which is highly desirable for Wavelength Division Multiplexing (WDM) in optical amplifiers. The unique optical properties of the powders at this temperature, are attributed to the formation of a metastable phase consisting of an uniform nano-scale dispersion of a metastable intermediate SiO₂ (Al,Er)₂O₃ phase in an amorphous SiO₂ matrix. At higher heat treatments (1400°C), a dual-phase equilibrium structure was formed, consisting of a pyrochlore phase in a crystobalite matrix.

Stimulated emission depletion (STED) population and polarisation dynamics are used to determine <α₄₀> the degree of hexadecapole alignment created in ensembles of rhodamine 6G molecules in solution following two-photon excitation. Hexadecapole molecular alignment is an unavoidable consequence of two-photon excitation but is not observed in spontaneous emission. For a single element diagonal transition tensor measurements of the fluorescence anisotropy R(t) in systems undergoing small step isotropic rotational diffusion can in principle be used to determine <α₄₀>. STED measurements of rhodamine 6G yield a value for <α₄₀> that is larger than that predicted for a single element transition tensor (SXX). Recent work in our laboratory indicates that whilst SXX is dominant SYY, SXY and SYX are finite, measurements of <α₄₀> appear to be a sensitive probe of the structure of the two-photon transition tensor. STED and fluorescence anisotropy measurements are extended to Rhodamine 6G in the isotropic phase of 5CB a system where small step isotropic rotational relaxation does not take place. Here the values of <α₄₀> are considerably larger. These results are discussed in terms of the initial hexadecapole alignment and <α₄₀> relaxation dynamics in a restricted geometry.

Zinc oxide (ZnO) is of great interest in photonic applications due to its wide bandgap (3.37 eV) and high exciton binding energy (60 meV). In the photoluminescence (PL) spectrum of ZnO, typically one UV band-edge emission peak and one or more peaks at the visible spectral range due to defect emission are observed. The PL emission of ZnO is commonly green, but other colors like yellow and orange are also reported. Out of the different visible peaks, the origin of the green one is the most controversial. The most commonly cited explanation for it is the transition between a singly oxidized oxygen vacancy and a photoexcited hole [K. Vanheusden, C. H. Seager, W. L. Warren, D. R. Tallant, and J. A. Voigt, Appl. Phys. Lett. 68, 403 (1996).]. However, this hypothesis is established on ZnO phosphors but not on nanostructured samples. In this work, several ZnO nanostructures (nanorods, nanoneedles, nanoshells and tetrapod nanorods) were synthesized by thermal evaporation and chemical methods. The obtained nanostructures were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), photoluminescence (PL), and electron paramagnetic resonance spectroscopy (EPR). It was found that fabrication methods significantly affect the defect emissions of the nanostructures. For different fabrication conditions, defect emissions in the green, yellow, and orange spectral ranges were observed. No correlation was found between the deep levels responsible for the visible emission and the EPR signal. Origins of the different defect emissions are discussed.

Oxide nanostructures can be prepared by various kinds of methods like thermal evaporation, vapor phase epitaxy, chemical synthesis, etc. Among various synthesis methods, hydrothermal method is of interest because it is simple and environmentally friendly. Also, it is performed at relatively low temperatures (<15⁰C), which is a significant advantage for device fabrication, in particular for hybrid organic/inorganic devices on flexible plastic substrates. In this work, nanostructures of various kinds of oxides: ZnO, CuO, NiO, and Ga₂O₃ were fabricated from aqueous solutions of the respective metal nitrate hydrate and hexamethylenetetramine. The obtained nanostructures were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The influence of solution concentration, synthesis temperature, and solution pH value on the obtained morphology and properties was investigated. Growth mechanisms and the factors affecting the structures of the investigated metal oxide nanostructures are discussed.

Optically transparent nanostructured SiO₂ glassceramics containing a high density of monodispersed, nanometer sized clusters of SnO₂ were obtained by phase separation from sol-gel synthesized xerogel. This material was produced either as bulk samples or as thin films on silicon and it can be easily doped with rare earth ions during the sol-gel synthesis. Spectroscopic measurements were carried out on bulk samples, demonstrating an effective energy-transfer between nanoclusters and rare earth ions. A particular sol-gel derived synthesis was employed, producing silica-based films with relatively low electrical resistivity and thickness ranging between 300 and 1000 nm. Suitable sol features allowed thick single-step deposition by spin-coating techniques, assuring the homogeneous nanosized clustering of the semiconducting SnO₂ phase. Refractive index and thickness were analyzed in films produced in different conditions of synthesis and thermal treatments of densification. The current-voltage response and the electro-induced optical emission in this material were investigated, suggesting potential technological applications in photonics and UV-emitting devices.

Silicon nanocrystals embedded in silicon dioxide matrices have exhibited optical gain in the visible region when pumped by a laser source, but to be commercially viable in laser applications and integration into microelectronics, emission has to be electrically stimulated rather than optically pumped. Superlattices of silicon and different non-silicon oxides were fabricated by pulsed laser deposition and subsequent rapid thermal annealing in inert atmosphere to obtain nanocrystalline silicon embedded in crystalline oxide layers. High resolution transmission electron microscopy was used to detect presence of silicon nanocrystals embedded in a silicon dioxide matrix. Reported in this letter are silicon nanocrystals with size from 3 nm to 7 nm obtained in Si/YSZ superlattices.

In the past few years, many studies have been carried out to use the ability of light to transport information into silicon-based integrated photonic circuits. The realization of an efficient silicon-based light source is therefore necessary but however challenging. Lasing cannot be easily achieved from silicon emission because of its indirect bandgap. Therefore, one solution proposed is to use other efficient emitters, like rare earth, into silicon or Silicon On Insulator based microcavities. Silica microdisk has been demonstrated to support high-Q whispering-gallery modes, and can be upgraded to ultra-high-Q toroidal microcavities by a CO2 laser melting process. Microdisk high Q-factor balances the low gain generally obtained from the active medium. Thus, those microcavities may be good candidates for silicon-based laser. In this paper, the fabrication and room temperature operation of silica microdisk associated with Er-doped silicon rich oxide is presented. Er atoms are excited at the 351 nm wavelength via the silicon clusters, giving to the material a high photonic capture section, and therefore a good photoluminescence efficiency. We demonstrate efficient coupling of erbium atoms to high-Q whispering-gallery modes. The photoluminescence spectrum is then theoretically treated. The WGM resonances are thus identified. We also discuss the contribution of the spot excitation and the weak coupling to the higher radial order modes. Finally, the polarization dependence of the observed modes is investigated, and the experimental results are compared to our analytical model of disk-shape cavities. Those results give us to think that an integrated laser should be soon achieved.

Colloidal biomimetic disc shaped metallic gold shells with a uniform size distribution were synthesized using red blood cells as sacrificial templates. Red blood cells do not reproduce by dividing; hence they are truly colloidal particles. They are almost completely filled with hemoglobin allowing for an extremely dynamic work cycle with long intercellular vacations separated by self-destructive workloads on the cell surface. This method of exchange is emulated in the presented research. The colloidal disc shaped gold shells were coated with multiple layers of 50nm fluorescent polystyrene spheres followed by chemical removal of the gold core. This process yielded hollow synthetic biomimetic membranes with a strong optical signature that are diffusely permeable to water and impervious to particles larger than a few nanometers. Currently, the most successful synthetic intravascular oxygen carrying materials are perfluorocarbons; however, they break down quickly in roughly 50 hours from overexposure to their in vivo workload. The meso-porous membrane cages will be filled with hundreds of fibrous spheroid conglomerates composed of perfluorocarbon chains that can protrude through the meso-porous membrane as they thermally jostle about the cage. This is to statistically limit the exposure time of individual polymer strands to the self-destructive work at the surface and hopefully will greatly increase the effective functioning lifetime of the perfluorocarbon-based synthetic red blood cell. The artificial membranes are intentionally designed to be weak allowing them to flex under normal pressures and to hopefully burst under more extreme conditions such as blockage.

It is well known by far that biological organisms could exhibit sophisticated optical system, which compete or overcame the top technology products available. The diatoms are microscopic algae enclosed in intricate amorphous silica cells, called frustules. In this work the optical reflectivity data, infrared spectroscopy, scanning electron microscopy and photoluminescence (PL) characterizations are presented for silica shells of Coscinodiscus wailesii, which is a centric diatom characterized from a diameter that varies in the range between 100 and 500 μm. Preliminary results suggest that the Coscinodiscus wailesii can be used as photonic material and sensor transducer.

An inexpensive, easily integrated, 40 Gbps photoreceiver operating in the communications band would revolutionize the telecommunications industry. While generation of 40 Gbps data is not difficult, its reception and decoding require specific technologies. We present a 40 Gbps photoreceiver that exceeds the capabilities of current devices. This photoreceiver is based on a technology we call "nanodust." This new technology enables nanoscale photodetectors to be embedded in matrices made from a different semiconductor, or directly integrated into a CMOS amplification circuit. Photoreceivers based on quantum dust technology can be designed to operate in any spectral region, including the telecommunications bands near 1.31 and 1.55 micrometers. This technology also lends itself to normal-incidence detection, enabling a large detector size with its associated increase in sensitivity, even at high speeds and reception wavelengths beyond the capability of silicon.

We have shown that ionic self-assembled multilayers (ISAMs) deposited on optical fiber long period gratings (LPGs) yield dramatic resonant-wavelength shifts, even with nanometer-thick films. Precise control of the refractive index and the thickness of these films was achieved by altering the relative fraction of the anionic and cationic materials combined with layer-by-layer deposition. We demonstrate the feasibility of this highly controllable deposition-technique for fine-tuning grating properties for grating applications. In addition, we confirm theoretically that the resonant wavelength shift can result from either the variation of the thickness of the film and/or the variation of its refractive index. Finally, we demonstrate that ISAMs adsorbed on LPGs function effectively as biosensors. These simulations and experimental results confirm that ISAM-coated-LPGs provide a thermally-stable, reusable, robust, and attractive platform for building efficient fiber optic sensors and devices.

We report on the physical modelling of the photoconductive response of nanostructured sol-gel films in function of the silver nitrate concentration (ions and colloids). This model considers several factors as the silver nitrate concentration and the transport parameters obtained. The model is compared with others commonly used. 2d-hexagonal nanostructured sol-gel thin films were prepared by dip-coating method using a non-ionic diblock copolymer Brij58 (surfactant) to produce channels into the film. Silver colloids (metallic Ag⁰ nanoparticles ) were obtained by spontaneous reduction process of Ag⁺ ions to Ag⁰. These nanoparticles were deposited into the channels formed by the surfactant. The structure was identified by X-ray diffraction and TEM. An absorption band located at 430 nm was detected by optical absorption; it corresponds to the plasmon surface. Fit to this band with modified Gans theory is presented. Photoconductivity studies were performed on films with silver ions and films with silver colloids to characterized their mechanisms of charge transport in the darkness and under illumination at 420, 633 nm wavelengths. Transport parameters were calculated. The films with silver colloids exhibit a photovoltaic effect stronger than the films with silver ions. While, the last ones possesses a photoconductivity behaviour.

The paper deals with 2D numerical modeling of Si-SiO₂ MOSFET for considering the field dependent mobility of the carriers in the surface channel. The fundamental device equations have been numerically solved to obtain various characteristics and parameters. The surface potential and electric field profile in the channel have been numerically estimated to have indepth analysis. The model enables one to estimate various parameters which determine the potential use of this device for various applications. The noise analysis of the device has been carried out to study the performance of the device. The exact solution of the 2D Poisson's equation for the S_i-S_iO₂ MOSFET's is derived by using Liebmann's iteration method. Based on the derived 2D potential distribution, the surface potential distribution in the S_i film is numerically obtained and their accuracy is verified by 2D analytical analysis. The calculated minimum surface potential and its location are used to analyze the drain-induced barrier-lowering effect and further to develop numerical threshold - voltage model. It is shown that excellent agreements are obtained for wide ranges of device structure parameters and applied biases.

The incorporation of photochromic dyes in mesostructured silica particles and the subsequent incorporation of the particles in latex to create solid films with relatively large, yet controllable, thickness, was recently reported [N. Andersson, P. C. A. Alberius, J. Skov Pedersen, L. Bergstroem, Microporous and Mesoporous Materials, 2004, 72, 175-183; N. Andersson, P. Alberius, J. Oertegren, M. Lindgren, L. Bergstroem, J. Mater. Chem., 2005, in press.] As photochromic dyes, spirooxazine (SO) and spiropyran (SP) were used. The films are transparent in day-light at room temperature and become coloured upon UV exposure. The films have a potential for usage as display systems, optical switches and optical memory devices. The synthesis of the SO/SP doped silica particles and the making of solid films is briefly described, and the spectral properties of SO/SP in various environments - in the film, in solution, as pristine dye powder and as silica particle powder - were studied by absorbance and fluorescence measurements, including time-resolved fluorescence decay measurements. It was found that the spectral properties of the photo-chromic dyes in the films are similar to those observed in solution, indicating that they are well-dispersed in the organic phase of the silica particles, which, in turn, are well-dispersed in the latex film.