Search results for "campi elettromagnetici"
showing 10 items of 155 documents
The EuroSTARRS airborne campaign in support of the SMOS mission: first results over land surfaces
2004
A number of experiments using ground-based and airborne sensors have shown the high potential of L-band passive microwave radiometry for estimating and monitoring surface soil moisture. This has led to the Soil Moisture and Ocean Salinity (SMOS) mission, a European Space Agency (ESA) Earth Explorer Opportunity mission. SMOS has the objective to observe soil moisture over land and sea surface salinity over sea, both key parameters for atmospheric, oceanographic and hydrological predictive models. In preparation of SMOS, the EuroSTARRS airborne campaign was carried out in November 2001. Multi-angular measurements of the surface brightness temperature at L-band (1.4 GHz) at vertical polarizati…
Tailoring Third-Harmonic Diffraction Efficiency by Hybrid Modes in High-Q Metasurfaces
2021
Metasurfaces are versatile tools for manipulating light; however, they have received little attention as devices for the efficient control of nonlinearly diffracted light. Here, we demonstrate nonlinear wavefront control through third-harmonic generation (THG) beaming into diffraction orders with efficiency tuned by excitation of hybrid Mie-quasi-bound states in the continuum (BIC) modes in a silicon metasurface. Simultaneous excitation of the high-Q collective Mie-type modes and quasi-BIC modes leads to their hybridization and results in a local electric field redistribution. We probe the hybrid mode by measuring far-field patterns of THG and observe the strong switching between (0,-1) and…
Design and development of a fNIRS system prototype based on SiPM detectors
2014
Functional Near Infrared Spectroscopy (fNIRS) uses near infrared sources and detectors to measure changes in absorption due to neurovascular dynamics in response to brain activation. The use of Silicon Photomultipliers (SiPMs) in a fNIRS system has been estimated potentially able to increase the spatial resolution. Dedicated SiPM sensors have been designed and fabricated by using an optimized process. Electrical and optical characterizations are presented. The design and implementation of a portable fNIRS embedded system, hosting up to 64 IR-LED sources and 128 SiPM sensors, has been carried out. The system has been based on a scalable architecture whose elementary leaf is a flexible board …
Scalable Electro-Optic Control of Localized Bistable Switching in Broad-Area VCSELs Using Reconfigurable Funnel Waveguides
2017
We demonstrate a steplike optical modulation based on the activation and deactivation of a bistable localized structure using a photoinduced and reconfigurable miniaturized 30 × 30 μm electroactivated funnel waveguide. Control of a single 10-μm-diameter spot in a 200-μm-diameter vertical-cavity surfaceemitting laser at 980 nm is achieved modulating the phase of an exciting beam in the specific position of the spot in the cavity. This localized on-off response can be scaled into arrays and offer a possible route to fast integrated optical logical functions and memory at low intensities at near-infrared wavelengths.
Reconfigurable nonlinear response of dielectric and semiconductor metasurfaces
2021
Abstract Optically resonant dielectric and semiconductor metasurfaces are an emerging and promising area of nanophotonics and light–matter interaction at the nanoscale. Recently, active tuning of the linear response and nonlinear effects of these components has received an increasing amount of interest. However, so far these research directions have remained separated with only few sporadic works that study their combination beginning to appear in the literature. The evolution of nonlinear metasurfaces based on dielectric and semiconductor materials toward reconfigurable and dynamic components could potentially answer the demand of integrated on-chip components that realize essential functi…
LA SENTINELLA GLOBALE. I campi elettromagnetici del MUOS di Niscemi e i loro effetti.
2017
Il MUOS (Mobile User Objective System), un radar installato in Sicilia proprio all’interno della riserva “sughereta di Niscemi”, è una delle quattro sentinelle del sistema globale che la Us Navy ha realizzato nei vari angoli del mondo per tenere sott’occhio tutto il pianeta. La storia di questo impianto è fatta di promesse non mantenute, di interventi politici pro MUOS poi sconfessati dalla magistratura, di proteste organizzate nel tentativo di interloquire con quei poteri, che pure erano sembrati disponibili. Al fondo delle azioni del movimento NO MUOS, che qui vengono ricordate insieme all’analogo caso di Radio Vaticana che all’inizio degli anni Duemila scosse il mondo politico italiano, …
Design and development of a continuous wave functional near infrared spectroscopy system
2014
Functional Near InfraRed Spectroscopy uses light sources and optical detectors for human brain monitoring. In this paper, a portable, low cost, battery-operated, multi-channel, continuous wave fNIRS embedded system, hosting up to 64 LED sources and 128 Silicon PhotoMultiplier optical detectors, is reported on. The designed system is based on a scalable architecture, in which each probe consists of 8 modular and flexible stands, able to host 4 bi-color LEDs as light sources, 16 silicon photomultipliers as photodetectors and a temperature sensor. The hardware structure allows to easily set up several relevant parameters: the timing of the LEDs, the optical power emitted by the LEDs; the acqui…