arXiv subjects

David Grosso

Publications and source records attributed to David Grosso.

5 recordsLinked to original sources

arXiv2026

Sequential Multi-Step Nanoimprint Lithography Fabrication of Zero-Mode Waveguide Nanoaperture Arrays to Enhance Single Molecule Fluorescence Detection

Zero-mode waveguides (ZMWs) enable single-molecule fluorescence detection at micromolar concentrations by confining light to nanoscale volumes, overcoming the diffraction limit of confocal microscopy. However, their widespread adoption is hindered by high fabrication costs and limited throughput of traditional methods like focused ion beam or electron-beam lithography. Here, we introduce a scalable cost-effective approach using sequential nanoimprint lithography (NIL) combined with hydrofluoric acid etching to fabricate ZMW arrays with tunable diameters from a single initial master. In our sequential nanoimprint approach, each stamped NIL output serves as a master for the next nanoimprint generation. By leveraging the shrinkage of sol-gel nanopatterns during annealing, we achieve a cumulative diameter reduction from 230 nm to 115 nm over four successive imprints, all based on the same initial master. The resulting ZMWs exhibit detection volumes reduced by up to 1000-fold and fluorescence enhancement exceeding 16x, achieving performance comparable to state-of-the-art focused ion beam-fabricated devices. Eliminating the need for multiple master structures significantly expands the scalability of nanoimprint lithography approaches. By lowering the nanofabrication barriers and making ZMW arrays more accessible, the sequential NIL method paves the way towards broader adoption of nanophotonic devices in single-molecule biophysics, biosensing, and surface patterning applications.

physics.optics↗

arXiv2024

Investigation of the anatase-to-rutile transition for TiO$_2$ sol-gel coatings with refractive index up to 2.7

This work describes the elaboration of rutile titanium dioxide films with high refractive indices and low scattering by sol-gel process and controlled crystallization. The evolutions of the optical properties and crystalline structure of sol-gel processed titania coatings on fused silica were investigated for different thermal budgets of the annealing post-treatment using ellipsometry, spectrophotometry, X-ray diffraction and electronic microscopy. It reveals that anatase and rutile coatings with refractive indices of 2.5 and 2.7 can be prepared with associated optical loss of 0.5% and 1%, respectively, which are excellent compromise for applications in integrated photonics. These evolutions are associated to the thermally induced mass transfer and phase transitions occurring during thermal annealing that involves first the nucleation growth and sintering of anatase polyoriented nanocrystals, followed by the transformation into rutile polyoriented nanocrystals. Concomitantly, rutile crystals with (110) faces parallel to the surface consume surrounding anatase and rutile nanocrystals by diffusive sintering to yield micron-size rutile monocrystalline and monooriented platelets patchwork, exhibiting refractive index of 2.73 and 1.2% optical loss. The formation of these platelets is governed by surface energies and is responsible for the increase in optical loss.

physics.optics↗

arXiv2023

Back-Propagation Optimization and Multi-Valued Artificial Neural Networks for Highly Vivid Structural Color Filter Metasurfaces

We introduce a novel technique for designing color filter metasurfaces using a data-driven approach based on deep learning. Our innovative approach employs inverse design principles to identify highly efficient designs that outperform all the configurations in the dataset, which consists of 585 distinct geometries solely. By combining Multi-Valued Artificial Neural Networks and back-propagation optimization, we overcome the limitations of previous approaches, such as poor performance due to extrapolation and undesired local minima. Consequently, we successfully create reliable and highly efficient configurations for metasurface color filters capable of producing exceptionally vivid colors that go beyond the sRGB gamut. Furthermore, our deep learning technique can be extended to design various pixellated metasurface configurations with different functionalities.

physics.optics↗

arXiv2021

Titania-Based Spherical Mie Resonators Elaborated by High-Throughput Aerosol Spray: Single Object Investigation

In the framework of photonics with all-dielectric nanoantennas, sub-micro-metric spheres can be exploited for a plethora of applications including vanishing back-scattering, enhanced directivity of a light emitter, beam steering, and large Purcell factors. Here, the potential of a high-throughput fabrication method based on aerosol-spray is shown to form quasi-perfect sub-micrometric spheres of polycrystalline TiO 2 . Spectroscopic investigation of light scattering from individual particles reveals sharp resonances in agreement with Mie theory, neat structural colors, and a high directivity. Owing to the high permittivity and lossless material in use, this method opens the way toward the implementation of isotropic meta-materials and forward-directional sources with magnetic responses at visible and near-UV frequencies, not accessible with conventional Si- and Ge-based Mie resonators.

physics.optics↗

arXiv2017

Converting water adsorption and capillary condensation in useable forces with simple porous inorganic thin films

This work reports an innovative humidity driven actuation concept based on Bangham effect using simple nanoporous sol-gel silica thin films as humidity responsive materials. Bilayer shaped actuators, consisting on a humidity-sensitive active nanostructured silica film deposited on a polymeric substrate (Kapton) were demonstrated as an original mean to convert water molecule adsorption and capillary condensation in useable mechanical work. Reversible silica surface energy modifications by water adsorption and the energy produced by the rigid silica film contraction, induced by water capillary condensation in mesopores, were finely controlled and used as the energy sources. The influence of the film nanostructure (microporosity, mesoporosity) and thickness, and of the polymeric support thickness, on the actuation force, on the movement speed, and on the amplitude of displacement are clearly evidenced and discussed. We show that the global mechanical response of such silica-based actuators can be easily adjusted to fabricate a humidity variation triggered tailor-made actuation systems. This first insight in hard ceramic stimulus responsive materials may open the door toward new generation of surface chemistry driven actuation systems.

cond-mat.soft↗