1,720,966 research outputs found
Design of nanodevices for sensing applications
Full text linkPlasmonically active SERS substrates, such as metallic gratings or MetaMaterials like Split Ring Resonators, have sub-wavelength features that enable direct coupling of normally incident electromagnetic radiation to surface plasmons. The high detection sensitivity of these methods exploits the EM field enhancements which arise in the proximity of the metallic nanostructures.
The object of the PhD research is the design, fabrication and characterization of plasmonic nanostructures to be used as biosensors.
In order to fabricate SERS-active substrates suitable for sensing applications, a well-tested nanofabrication process for the realization of easily manufacturable and reproducible devices has been developed, exploring the different mechanisms of light transmission through 1D digital metallic gratings in order to optimize the optical response and efficiency of the devices.
1D digital gold grating devices, able to concentrate the electromagnetic radiation inside the slits, have been fabricated. The SERS Enhancement Factor of the realized nanostructures and its dependence on a generic hybrid polarization have been measured and compared with the theoretical estimations.
A good agreement between the experimental and numerical estimations, added up to a well-tested nanofabrication process able to guarantee a good uniformity and reproducibility of the device, has confirmed the potentiality of the nanofabrication technique in substrate engineering to provide local fields of the desired intensity and location.
Finally, novel types of sensing nanodevices, coupling biosensing to MetaMaterials properties have been realized, to explore the peculiar properties of such kind of structures in combination with plasmonic nano-optics.
These type of sensors would likelihood represent a promising step toward future reproducible single-molecule detection using engineered plasmonic substratesSubstrati SERS plasmonicamente attivi, come grating metallici o MetaMateriali quali Split Ring Resonators, hanno caratteristiche sub-wavelength che consentono l'accoppiamento diretto tra radiazione elettromagnetica normalmente incidente e plasmoni di superficie. L'elevata sensibilità di rivelazione di questi metodi sfrutta l’incremento del campo EM che si origina in prossimità di nanostrutture metalliche.
L'oggetto della ricerca di dottorato è la progettazione, fabbricazione e caratterizzazione di nanostrutture plasmoniche per applicazioni biosensoristiche.
Allo scopo di fabbricare substrati SERS-attivi adatti per applicazioni di tipo sensoristico, è stato sviluppato un collaudato processo di nanofabbricazione in grado di consentire la realizzazione di dispositivi facilmente fabbricabili e riproducibili. Ciò ha richiesto lo studio e la comprensione dei diversi meccanismi di trasmissione della luce attraverso reticoli metallici digitali unidimensionali al fine di ottimizzare la risposta ottica e l'efficienza dei dispositivi.
Sono stati fabbricati dispositivi costituiti da grating d'oro unidimensionali in grado di concentrare la radiazione elettromagnetica all’interno delle fenditure ed è stato misurato e confrontato con stime teoriche il fattore di enhancement SERS delle nanostrutture realizzate e la sua dipendenza da una polarizzazione ibrida generica.
Un buon accordo tra le stime numeriche e sperimentali, assieme ad una tecnica di nanofabbricazione collaudata in grado di garantire una buona uniformità e riproducibilità del processo, conferma le potenzialità della tecnica nell’ingegnerizzazione di substrati per la generazione di campi locali dell’intensità e della distribuzione desiderata.
Sono stati infine realizzati nuovi tipi di nanosensori allo scopo di accoppiare le proprietà biosensoristiche con quelle dei MetaMateriali, in modo da studiare le proprietà peculiari di questo tipo di strutture se combinate con nano-ottiche plasmoniche.
Questo tipo di sensori rappresentano un passo promettente verso una possibile futura rivelazione di singole molecole tramite ingegnerizzazione di substrati plasmonici
Compact sorting of optical vortices by means of diffractive transformation optics
No full textThe orbital angular momentum (OAM) of light has recently attracted a growing interest as a new degree of freedom in order to increase the information capacity of today's optical networks, both for free-space and optical fiber transmission. Here we present our work of design, fabrication, and optical characterization of diffractive optical elements for compact OAM mode division demultiplexing based on optical transformations. Samples have been fabricated with 3D high-resolution electron beam lithography on a polymethylmethacrylate resist layer spun over a glass substrate. Their high compactness and efficiency make these optical devices promising for integration into next-generation platforms for OAM modes processing in telecom applications
Generation of high-order Laguerre-Gaussian modes by means of spiral phase plates
Full text linkSpiral phase plates for the generation of Laguerre-Gaussian (LG) beam with non-null radial index were designed and fabricated by electron beam lithography on polymethylmethacrylate over glass substrates. The optical response of these phase optical elements was theoretically considered and experimentally measured, and the purity of the experimental beams was investigated in terms of LG modes contributions. The far-field intensity pattern was compared with theoretical models and numerical simulations, whereas interferometric analyses confirmed the expected phase features of the generated beams. The high quality of the output beams confirms the applicability of these phase plates for the generation of high-order LG beams
Diffractive optics for combined spatial- and mode- division demultiplexing of optical vortices: design, fabrication and optical characterization
Full text linkDuring the last decade, the orbital angular momentum (OAM) of light has attracted growing interest as a new degree of freedom for signal channel multiplexing in order to increase the information transmission capacity in today's optical networks. Here we present the design, fabrication and characterization of phase-only diffractive optical elements (DOE) performing mode-division (de)multiplexing (MDM) and spatial-division (de)multiplexing (SDM) at the same time. Samples have been fabricated with high-resolution electron-beam lithography patterning a polymethylmethacrylate (PMMA) resist layer spun over a glass substrate. Different DOE designs are presented for the sorting of optical vortices differing in either OAM content or beam size in the optical regime, with different steering geometries in far-field. These novel DOE designs appear promising for telecom applications both in free-space and in multi-core fibers propagation
Fabrication and characterization of high-quality spiral phase plates for optical applications
No full textSpiral phase plates with radial discontinuities for the generation of multiring orbital angular momentum beams: Fabrication, characterization, and application
No full textDiffractive optics for OAM-mode division multiplexing of optical vortices Design, fabrication and optical characterization
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Test of mode-division multiplexing and demultiplexing in free-space with diffractive transformation optics
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