Exciton Control in a Room-Temperature Bulk Semiconductor with Coherent Strain Pulses

The coherent manipulation of excitons in bulk semiconductors via the lattice degrees of freedom is key to the development of acousto-optic and acousto-excitonic devices. Wide-bandgap transition metal oxides exhibit strongly bound excitons that are interesting for applications in the deep-ultraviolet, but their properties have remained elusive due to the lack of efficient generation and detection schemes in this spectral range. Here, we perform ultrafast broadband deep-ultraviolet spectroscopy on anatase TiO$_2$ single crystals at room temperature, and reveal a dramatic modulation of the exciton peak amplitude due to coherent acoustic phonons. This modulation is comparable to those of nanostructures where exciton-phonon coupling is enhanced by quantum confinement, and is accompanied by a giant exciton shift of 30-50 meV. We model these results by many-body perturbation theory and show that the deformation potential coupling within the nonlinear regime is the main mechanism for the generation and detection of the coherent acoustic phonons. Our findings pave the way to the design of exciton control schemes in the deep-ultraviolet with propagating strain pulses

Ultrafast Acousto-Plasmonics in Gold Nanoparticles Superlattice

We report the investigation of the generation and detection of GHz coherent acoustic phonons in plasmonic gold nanoparticles superlattices (NPS). The experiments have been performed from an optical femtosecond pump-probe scheme across the optical plasmon resonance of the superlattice. Our experiments allow to estimate the collective elastic response (sound velocity) of the NPS as well as an estimate of the nano-contact elastic stiffness. It appears that the light-induced coherent acoustic phonon pulse has a typical in-depth spatial extension of about 45 nm which is roughly 4 times the optical skin depth in gold. The modeling of the transient optical reflectivity indicates that the mechanism of phonon generation is achieved through ultrafast heating of the NPS assisted by light excitation of the volume plasmon. These results demonstrate how it is possible to map the photon-electron-phonon interaction in subwavelength nanostructures

Railways' stability observed in Campania (Italy) by InSAR data

Campania region is characterized by intense urbanization, active volcanoes, subsidence, and landslides; therefore, the stability of public transportation structures is highly concerned. We have app..

Railways’ Stability Observation by Satellite Radar Images

Remote sensing has many vital civilian applications. Space-borne Interferometric Synthetic Aperture Radar has been used to measure the Earth’s surface deformation widely. In particular, Persistent Scatterer Interferometry (PSI) is designed to estimate the temporal characteristics of the Earth’s deformation rates from multiple InSAR images acquired over time. This chapter reviews the space-borne Differential Interferometric Synthetic Aperture Radar techniques that have shown their capabilities in monitoring of railways displacements. After description of the current state of the art and potentials of the available radar remote sensing techniques, one case study is examined, pertaining to a railway bridge in the Campania region, Italy

river morphology monitoring using multitemporal sar data preliminary results

AbstractIn this paper, we test the capability of satellite synthetic aperture radar (SAR) images to enhance the monitoring of river geomorphological processes. The proposed approach exploits the recently introduced Level-α products. These products are bi-temporal RGB composites in which the association color-object, being physical-based, is stable whatever the scene is considered. This favors the detection of temporary rivers' characteristics for classification purposes in a change-detection environment. The case study was implemented on the Orco river (northwest Italy), where a set of 39 COSMO-SkyMed SAR stripmap images acquired from October 2008 to November 2014 was used to monitor channel planform changes. This preliminary study is devoted to assess the suitability of Level-α images for geomorphologist, with particular reference to the detection of phenomena of interest in river monitoring. This is prior for semi-automatic or automatic classification activities

Prediction of Persistent Organic Pollutants Biodegradation in Contaminated Marine Sediments Using Passive Sampling Probes

The aim of this study is to evaluate a new configuration (new materials) of the commercial passive sampler Chemcatcher as probe for predicting the bioavailability of persistent organic pollutants in marine sediments. To predict the availability of pollutants to biota, it is important to understand both solution- and solid-phase processes in the sediment, including the kinetics of pollutants release from its binding agent (ligand and/or particle). The present study examined the kinetic of desorption and biodegradation of Polycyclic Aromatic Hydrocarbons (PAHs) in two different marine sediments sampled in the Adriatic Sea. The sediments were spiked with a standard mix of 16 PAHs in the range of 11-12 mg/Kg (dry sediment). Formaldehyde was added into the sediments to prevent biodegradation. After equilibration, the passive probes were placed in the specimens with prevented biodegradation, recovered and analyzed at prefixed time slots (in the range of 50 days) for the assessment of the accumulated PAHs; in parallel a little amount of sediments was collected and the residual concentration of PAHs was measured. Free PAHs in the sediment pore waters were also determined. The results suggest that the kinetically labile solid-phase pool of PAHs, which is included in the DGT measurement, played an important role in biodegradation processes along with the free PAHs in sediment pore water