Mechanism of surface plasmon polarition propagation for nano-optics applications

In recent times a new emerging research field has become more and more popular in the optics community, which is plasmonics. This discipline studies the surprising optical properties of metals at the nano-scale, which are substantially different from those at the macro-scale. This thesis presents several theoretical/numerical studies in the field of plasmonics, both with fundamental research and with applicative purposes in the fields of photovoltaics and sensing. One basic problem in plasmonics is the study of optical Bloch modes of planar arrays of metallic nanostructures, namely periodic in one or two dimensions but not in the third, what are called plasmonic crystal slabs. We present here a finite-elements-based numerical method for the modal analysis of such structures, which allows to retrieve complex Bloch modes dispersions both of truly bound optical modes and of leaky modes. We present then a thorough investigation of the optical properties of a well-known plasmonic crystal, which is the 1-D lamellar grating. Our main interest here is the possible use of this structure as a light trapping device for photovoltaics applications. We consider its integration on top of a silicon solar cell and within a thin film organic solar cell. In both cases the mechanisms at the basis of the observed enhancement are analyzed in detail. In the former case, experimental evidence of the enhancement predicted by simulations is provided as well. For what concerns sensing applications, we carried out three fundamental studies. The first concerns metal-coated dielectric wedges for plasmonic nanofocusing. These structures allow at a time an efficient coupling of impinging light to surface plasmon polaritons and their nanofocusing at the ridge. Finite elements method (FEM) was used to design the structure, which has been fabricated by means of FIB milling combined with silicon anisotropic etching and replica molding. Near field, and Raman optical characterizations were used to verify the nanofocusing effect. The second study concerned the individuation and optimization of a plasmonic nanostructure suitable for the implementation in an optoelectronic biosensor based on a high electron mobility phototransistor (HEMT). Three different nanostructures were studied, maximizing their optical response to a surface refractive index variation. The best structure turned out to be an array of triangular grooves on a gold thick film, which has been finally fabricated and characterized in collaboration with the IOM-TASC Laboratory in Trieste. Finally we carried out a study of a class of nanostructures termed as plasmonic vortex lenses, constituted by spiral and circular grooves on a gold surface. The great interest in these structures stems from their ability to couple and focalize impinging circularly polarized light in the form of plasmonic vortices, impressing them an arbitrary orbital angular momentum. We focused in particular on the transmission of such a plasmonic vortices through a hole placed a the lens center, analyzing in detail the angular momentum properties of the transmitted field

Magnetic Control of Transmission and Helicity of Nano-Structured Optical Beams in Magnetoplasmonic Vortex Lenses

We theoretically investigate the generation of far-field propagating optical beams with a desired orbital angular momentum by using an archetypical magnetoplasmonic tip surrounded by a gold spiral slit. The use of a magnetic material can lead to important implications once magneto-optical activity is activated through the application of an external magnetic field. The physical model and the numerical study presented here introduce the concept of magnetically tunable plasmonic vortex lens, namely a magnetoplasmonic vortex lens, which ensures a tunable selectivity in the polarization state of the generated nanostructured beam. The presented system provides a promising platform for a localized excitation of plasmonic vortices followed by their beaming in the far-field with an active modulation of both light's transmittance and helicity

3d plasmonic nanoantennas integrated with mea biosensors

Plasmonic 3D nanoantennas are integrated on multielectrode arrays. These biosensors can record extracellular activity and enhance Raman signals from living neurons

Spatially, Temporally, and Quantitatively Controlled Delivery of Broad Range of Molecules into Selected Cells through Plasmonic Nanotubes

A Universal plasmonic/microfluidic platform for spatial and temporal controlled intracellular delivery is described. The system can inject/transfect the desired amount of molecules with an efficacy close to 100%. Moreover, it is highly scalable from single cells to large ensembles without administering the molecules to an extracellular bath. The latter enables quantitative control over the amount of injected molecules

Light-trapping in photon enhanced thermionic emitters

A series of photonic crystal structures are optimized for a photon enhanced thermionic emitter. With realistic parameter values to describe a p-type GaAs device we find an efficiency above 10%. The light-trapping structures increases the performance by 2% over an optimal bilayer anti-reflective coating. We find a device efficiency very close to the case of a Lambertian absorber, but below its maximum performance. To prevent an efficiency below 10% the vacuum gap must be dimensioned according to the concentration factor of the solar irradiance

Impact of renin-angiotensin system inhibitors on mortality during the COVID Pandemic among STEMI patients undergoing mechanical reperfusion : Insight from an international STEMI registry

Background: Concerns have been raised on a potential interaction between renin-angiotensin system inhibitors (RASI) and the susceptibility to coronavirus disease 2019 (COVID-19). No data have been so far reported on the prognostic impact of RASI in patients suffering from ST-elevation myocardial infarction (STEMI) during COVID-19 pandemic, which was the aim of the present study. Methods: STEMI patients treated with primary percutaneous coronary intervention (PPCI) and enrolled in the ISACS-STEMI COVID-19 registry were included in the present sub-analysis and divided according to RASI therapy at admission. Results: Our population is represented by 6095 patients, of whom 3654 admitted in 2019 and 2441 in 2020. No difference in the prevalence of SARSCoV2 infection was observed according to RASI therapy at admission (2.5% vs 2.1%, p = 0.5), which was associated with a significantly lower mortality (adjusted OR [95% CI]=0.68 [0.51 & ndash;0.90], P = 0.006), confirmed in the analysis restricted to 2020 (adjusted OR [95% CI]=0.5[0.33 & ndash;0.74], P = 0.001). Among the 5388 patients in whom data on in-hospital medication were available, in-hospital RASI therapy was associated with a significantly lower mortality (2.1% vs 16.7%, OR [95% CI]=0.11 [0.084 & ndash;0.14], p < 0.0001), confirmed after adjustment in both periods. Among the 62 SARSCoV-2 positive patients, RASI therapy, both at admission or in-hospital, showed no prognostic effect. Conclusions: This is the first study to investigate the impact of RASI therapy on the prognosis and SARSCoV2 infection of STEMI patients undergoing PPCI during the COVID-19 pandemic. Both pre-admission and in-hospital RASI were associated with lower mortality. Among SARSCoV2-positive patients, both chronic and in-hospital RASI therapy showed no impact on survival.Peer reviewe

Mechanism of surface plasmon polarition propagation for nano-optics applications

In recent times a new emerging research field has become more and more popular in the optics community, which is plasmonics. This discipline studies the surprising optical properties of metals at the nano-scale, which are substantially different from those at the macro-scale. This thesis presents several theoretical/numerical studies in the field of plasmonics, both with fundamental research and with applicative purposes in the fields of photovoltaics and sensing. One basic problem in plasmonics is the study of optical Bloch modes of planar arrays of metallic nanostructures, namely periodic in one or two dimensions but not in the third, what are called plasmonic crystal slabs. We present here a finite-elements-based numerical method for the modal analysis of such structures, which allows to retrieve complex Bloch modes dispersions both of truly bound optical modes and of leaky modes. We present then a thorough investigation of the optical properties of a well-known plasmonic crystal, which is the 1-D lamellar grating. Our main interest here is the possible use of this structure as a light trapping device for photovoltaics applications. We consider its integration on top of a silicon solar cell and within a thin film organic solar cell. In both cases the mechanisms at the basis of the observed enhancement are analyzed in detail. In the former case, experimental evidence of the enhancement predicted by simulations is provided as well. For what concerns sensing applications, we carried out three fundamental studies. The first concerns metal-coated dielectric wedges for plasmonic nanofocusing. These structures allow at a time an efficient coupling of impinging light to surface plasmon polaritons and their nanofocusing at the ridge. Finite elements method (FEM) was used to design the structure, which has been fabricated by means of FIB milling combined with silicon anisotropic etching and replica molding. Near field, and Raman optical characterizations were used to verify the nanofocusing effect. The second study concerned the individuation and optimization of a plasmonic nanostructure suitable for the implementation in an optoelectronic biosensor based on a high electron mobility phototransistor (HEMT). Three different nanostructures were studied, maximizing their optical response to a surface refractive index variation. The best structure turned out to be an array of triangular grooves on a gold thick film, which has been finally fabricated and characterized in collaboration with the IOM-TASC Laboratory in Trieste. Finally we carried out a study of a class of nanostructures termed as plasmonic vortex lenses, constituted by spiral and circular grooves on a gold surface. The great interest in these structures stems from their ability to couple and focalize impinging circularly polarized light in the form of plasmonic vortices, impressing them an arbitrary orbital angular momentum. We focused in particular on the transmission of such a plasmonic vortices through a hole placed a the lens center, analyzing in detail the angular momentum properties of the transmitted field.Recentemente un nuova emergente linea di ricerca è diventata sempre più di rilevo in ottica: la plasmonica. Questa disciplina studia le sorprendenti proprietà ottiche dei metalli alla nanoscala, che sono sostanzialmente differenti da quelle a scale macroscopiche, alle quali siamo abituati. Questa tesi presenta diversi studi teorico-numerici nel campo della plasmonica, con fini sia di ricerca di base, sia applicativi negli ambiti del fotovoltaico e della sensoristica. Un problema di fondamentale importanza in plasmonica è lo studio dei modi ottici di Bloch di array planari di nanostrutture metalliche, anche detti plasmonic crystal slabs. Presentiamo qui un metodo numerico, basato sulla tecnica degli elementi finiti, per l’analisi modale di tali strutture, tramite il quale è possibile calcolare le dispersioni complesse sia dei modi di Bloch puramente confinati, sia di quelli radiativi. Presentiamo poi un’estesa analisi delle proprietà ottiche di un ben noto cristallo plasmonico, ovvero il reticolo unidimensionale di nano-strisce metalliche. Ci focalizziamo in particolare sulla possibilità di usare tale nanostruttura come sistema di trapping della luce, per applicazioni al fotovoltaico. A tale scopo consideriamo l’integrazione in una cella solare a silicio cristallino e in una organica a film sottile. In entrambi i casi sono analizzati in dettaglio i meccanismi alla base dell’aumento di assorbimento della luce calcolato. Nel primo caso, inoltre, è fornita evidenza sperimentale dell’enhancement predetto teoricamente. Per quanto riguarda le applicazioni alla sensoristica, sono stati condotti tre studi di base. Il primo concerne nanocunei dielettrici ricoperti da un sottile strato metallico, atti ad ottenere l’effetto del nanofocusing plasmonico. Queste strutture permettono di accoppiare efficientemente la luce a plasmoni polaritoni di superficie che sono quindi focalizzati a dimensioni nanometriche sul bordo dei cunei stessi. Simulazioni agli elementi finiti hanno permesso di progettare la struttura, che è stata poi fabbricata attraverso un processo che combina litografia FIB, etching anisotropo del silicio e replica di stampi dielettrici. Tecniche di caratterizzazione in near field e Raman hanno evidenziato la presenza dell’effetto di nanofocusing desiderato. Il secondo studio ha riguardato l’individuazione e ottimizzazione di opportune nanostrutture plasmoniche adatte per l’implementazione in un biosensore basato su un fototransistor ad alta mobilità elettronica (HEMT). Sono state studiate tre diverse nanostrutture, massimizzando la loro risposta ottica a una variazione di indice di rifrazione superficiale. La migliore struttura si è rivelata un reticolo di solchi triangolari su uno strato d’oro. Tale struttura è stata fabbricata e caratterizzata in collaborazione con l’istituto IOM-TASC di Trieste. Per finire, si è studiata una classe di nanostrutture denominate lenti per vortici plasmonici, costituite da solchi a spirale o circolari praticati su una superficie metallica. Il forte interesse per queste strutture scaturisce dal fatto che sono in grado di accoppiare la luce incidente a plasmoni polaritoni di superficie, imprimendo al campo un momento angolare orbitale. Ci siamo concentrati in particolare sulla trasmissione dei vortici plasmonici attraverso lenti plasmoniche con un buco al centro, analizzando in dettaglio le proprietà di momento angolare del campo trasmesso