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Thin silica and silica-titania films doped with sulfide nanocrystals of controlled size were fabricated by a method based on the preparation of colloidal particles and their introduction into a glassy matrix through the sol-gel method. Colloidal sols of composition HgxCd1-xS and PbxCd1-xS (with x ranging from 0 to 1) were prepared and used to dope alkoxide solutions for the deposition of thin silica and silica-titania films. Optical absorption spectra were taken on both precursor colloidal sols and derived doped films. X-ray diffraction characterization gave structural information on the nature and size of particles in powders obtained by precipitation from colloidal sols and in doped films. The advantages and limits of the investigated systems are discussed in light of possible applications. The nonlinear properties of the most interesting PbS-doped planar waveguides have been investigated in the near-infrared, at 1.064 μm. A reversible nonlinear effect was measured, with n2 values ranging from -5 to -20×10-9 cm2/kW. [ABSTRACT FROM AUTHOR]

In this study, we report the use of Al₂O₃ nanoparticles in combination with fluorine doped tin oxide (F:SnO₂, aka FTO) thin films to form hazy Al₂O₃-FTO nanocomposites. In comparison to previously reported FTO-based nanocomposites integrating ZnO and sulfur doped TiO₂ (S:TiO₂) nanoparticles (i.e., ZnO-FTO and S:TiO₂-FTO nanocomposites), the newly developed Al₂O₃-FTO nanocomposites show medium haze factor H T of about 30%, while they exhibit the least loss in total transmittance T tot. In addition, Al₂O₃-FTO nanocomposites present a low fraction of large-sized nanoparticle agglomerates with equivalent radius r eq > 1 &mu;m; effectively 90% of the nanoparticle agglomerates show r eq < 750 nm. The smaller feature size in Al₂O₃-FTO nanocomposites, as compared to ZnO-FTO and S:TiO₂-FTO nanocomposites, makes them more suitable for applications that are sensitive to roughness and large-sized features. With the help of a simple optical model developed in this work, we have simulated the optical scattering by a single nanoparticle agglomerate characterized by bottom radius r₀, top radius r₁, and height h. It is found that r₀ is the main factor affecting the H T (&lambda;), which indicates that the haze factor of Al₂O₃-FTO and related FTO nanocomposites is mainly determined by the total surface coverage of all the nanoparticle agglomerates present.

It has been shown in literature that cross-shaped holes arrays can be made insensitive to polarization at normal incidence, and can even feature good stability for off-normal incidence. In this work we look for the optimal design rules to obtain high spectral stability conditions in the visible for those structures, through a complete review of all geometrical parameters using CMOS-compatible materials. Rigorous Coupled Wave Analysis (RCWA) simulations have been used to identify the most-impacting parameters and to determine typical ranges allowing for the realization of low-color errors image sensors whatever the light incidence. It appears that the two main parameters are the ratio of the arm width to the arm length of the crosses and the distance between crosses, which both have to be low to ensure stable responses of the filters. We demonstrate the results with CIE chromaticity diagrams reporting the responses of a RGB filter designed with the established rules under various illumination conditions.

Miniature optical components at the wavelength scale remain today a theoretically opened challenging problem of great technological interest. Appart from refractive micro-optics, plasmonics have been proposed to realize micro lenses with properly designed planar metallic nano-patterns. We show in this paper that efficient light focusing at the diffraction limit with higher transmission can be obtained with micro-structures much easier to fabricate than nano ones, such as a simple micro-slit studied here as an example. Optical properties are attributed to diffraction and a quantitative excellent agreement between experiment and theory is obtained.

We theoretically and experimentally demonstrate that the diffraction of microstructures based on silver nanowires leads to very efficient microfocusing effects. Pairs of parallel nanowires act as ultrasmall cylindrical microlenses with diffraction-limited resolution in the Fresnel region. This is a new diffraction scheme to make micron-sized optical lenses with higher transmittance than plasmonic microlens based on nano-aperture arrays. Calculations based on the scalar Rayleigh-Sommerfeld integral highlights the pure scalar diffractive contribution. Thus, the plasmon contribution is negligible in such micron-sized metallic geometry. We demonstrate that two-dimensional grids of nanowires can be used to fabricate dense arrays of microlenses, i.e. 10000x10000 DPI (dots per inch).

Archimedes micro-screws have been fabricated by three-dimensional two-photon polymerization using a Nd:YAG Q-switched microchip laser at 532nm. Due to their small sizes they can be easily manipulated, and made to rotate using low power optical tweezers. Rotation rates up to 40 Hz are obtained with a laser power of 200 mW, i.e. 0.2 Hz/mW. A photo-driven micropump action in a microfluidic channel is demonstrated with a non-optimized flow rate of 6 pL/min. The optofluidic properties of such type of Archimedes micro-screws are quantitatively described by the conservation of momentum that occurs when the laser photons are reflected on the helical micro-screw surface.