Alessandra Rocco - Academia.edu (original) (raw)

Papers by Alessandra Rocco

Procedia Engineering, 2014

2014 IEEE Metrology for Aerospace (MetroAeroSpace), 2014

ABSTRACT In this work, the application of Electronic Speckle Pattern Interferometry (ESPI) is emp... more ABSTRACT In this work, the application of Electronic Speckle Pattern Interferometry (ESPI) is employed for inspecting composite materials subject to thermal load. The composite samples are of interest in the aerospace industry. Through real-time surface illumination by visible laser (i.e. 532 nm), the ESPI technique allows the non-contact, non-destructive, full frame and real time detection of micro-deformations, micro-cracks, residual stress and delamination. The evaluation of the effective delaminated area of damaged polymer/Carbon Nanotubes fiber reinforced composites after flexural tests is presented.

Optics Express, 2012

We present a widely-tunable, singly-resonant optical parametric oscillator, emitting more than 1 ... more We present a widely-tunable, singly-resonant optical parametric oscillator, emitting more than 1 W between 2.7 and 4.2 μm, which is phase locked to a self-referenced frequency comb. Both pump and signal frequencies are directly phase-locked to the frequency comb of a NIR-emitting fs mode-locked fibre laser, linked, in turn, to the caesium primary standard. We estimate for the idler frequency a fractional Allan deviation of ∼ 3 × 10 −12 τ −1/2 between 1 and 200 s. To test the spectroscopic performance of the OPO, we carried out saturation spectroscopy of several transitions belonging to the ν 1 rovibrational band of CH 3 I, resolving their electronic quadrupole hyperfine structure, estimating a linewidth better than 200 kHz FWHM for the idler, and determining the absolute frequency of the hyperfine components with a 50-kHz-uncertainty.

NDT & E International, 1988

Dott. Alessandra Rocco Negative dispersion without absorption in atomic ensembles In this work th... more Dott. Alessandra Rocco Negative dispersion without absorption in atomic ensembles In this work the optical properties of a calcium atomic beam, strongly driven on the transition, are investigated, in order to obtain a coherently prepared medium with the right amount of negative dispersion at a point of zero absorption. From the theory it is well known that a strongly driven Two-Level system exhibits such properties. Such a medium could in particular be used to fill an optical resonator in order to obtain a broadband high finesse cavity (White Light Cavity). For the investigations a spectroscopic method had been used, consisting of a Mach-Zehnder interferometer with a phase modulated arm. In this way it is possible to perform a high sensitive simultaneous measurement of both phase shift and absorption profiles in a calcium atomic beam, for an increasing driving field, which frequency is stabilized on the transition 4s2 S0 4s4p P1 at 423nm. For the first time both absorption and phase...

WIT Transactions on the Built Environment, 2005

As demonstrated by many lectures, seismic and volcanic phenomena are strongly related to ground d... more As demonstrated by many lectures, seismic and volcanic phenomena are strongly related to ground deformation and gaseous emissions. Thus to mitigate environmental risks, a continuous monitoring of ground strain and of the changes in the composition of gaseous emissions can be a very useful tool. The SIMONA (Environmental Integrated Monitoring System) Project aims at fixing, realizing and experimenting an innovative regional monitoring system, based on innovative optoelectronic devices, which is able to exceed the existing limits in order to increase sensibly the interpretation of geo-physical phenomena and the long term mitigation of seismic and volcanic hazards.

Measurement Science and Technology, 2015

ABSTRACT The aim of this paper is to investigate the ability of different NDT techniques to detec... more ABSTRACT The aim of this paper is to investigate the ability of different NDT techniques to detect and evaluate barely visible and non-visible impact damage on composite laminates. Firstly, a conventional ultrasound technique was adopted to investigate the delamination in carbon fibre laminates after low velocity impact s. Then the results were compared with a thermographic and holographic analysis, as well as a theoretical simulation of the expected delamination. The results were compared and discussed. Overall a good agreement was found between the data obtained by the different techniques. Furthermore, the true values of the damage parameters were confirmed by DT performed on the samples.

Journal of the European Optical Society: Rapid Publications, 2007

Making use of an interferometric diagnostic system, we analyze the thermo-mechanical distortions ... more Making use of an interferometric diagnostic system, we analyze the thermo-mechanical distortions taking place in the slab shaped ceramic Nd:YAG active medium of a 100 W class laser. These distortions are collected in different pumping regimes, both in static situations and during transient warm-up, and compared to the results of computer simulations. This procedure enables us to determine the relevance of different stress causes and thus to increase the specific power extraction of the active slab module.

Optical Sensing, 2004

Recent progress in telecom-based optoelectronic devices and low power laser sources has provided ... more Recent progress in telecom-based optoelectronic devices and low power laser sources has provided new powerful tools for in-situ monitoring of volcanic areas in real-time and for long periods, with unprecedented accuracy and resolution. Such techniques represent a great improvement if compared to the traditionally used &amp;amp;amp;amp;amp;amp;amp;quot;in-situ&amp;amp;amp;amp;amp;amp;amp;quot; sampling techniques such as gas chromatography and mass spectrometry which result often impractical or

The concentration of CO2 and H2O have been monitored during a four-days campaign in Vulcano (Eoli... more The concentration of CO2 and H2O have been monitored during a four-days campaign in Vulcano (Eolian Archipelago, Sicily), by means of a portable spectrometer based on a semiconductor diode laser operating at a wavelength of 2 ?Ym. The spectrometer was able to work both in open-path configuration and as an accumulation chamber. In-situ measurements were made at different heights from

From November 29th to December 1st 2006, a gas monitoring experiment was carried out at the Solfa... more From November 29th to December 1st 2006, a gas monitoring experiment was carried out at the Solfatara volcano (Pozzuoli, Italy). The primary objectives were to prove that monitoring is possible with the experimental set-up described below, and to compare the new data obtained with those from earlier continuos gas monitoring carried out in November 2001. Temperature measurements and gas extraction

While continuous geophysical monitoring have become widely accepted as major tools for volcanolog... more While continuous geophysical monitoring have become widely accepted as major tools for volcanological forecasting, geochemical surveillance of volcanic activity is still less frequently applied. Investigations on the chemistry and mineralogy of fumaroles gas and sublimates as well as isotopic investigations of volcanic gas sampled at Solfatara volcano (Campi Flegrei southern Italy) were performed using various methodologies prevailing on monthly/weekly basis

... GAS SENSORS FOR ENVIRONMENTAL MONITORING Maurizio De Rosa*, Gianluca Gagliardi, Pasquale Madd... more ... GAS SENSORS FOR ENVIRONMENTAL MONITORING Maurizio De Rosa*, Gianluca Gagliardi, Pasquale Maddaloni, Pietro Malara, Alessandra Rocco and Paolo ... of Gases Direct laser absorption spectroscopy used for quantitative measurements is based on Lambert-Beer law. ...

SPIE Proceedings, 2012

ABSTRACT We present a widely-tunable, singly-resonant optical parametric oscillator, emitting mor... more ABSTRACT We present a widely-tunable, singly-resonant optical parametric oscillator, emitting more than 1 W in the region between 2.7 and 4.2 μm. Two configurations have been studied in order to improve the frequency stability and the linewidth of the OPO emission. First, we stabilized the signal frequency to a high-finesse Fabry-Perot cavity. Then, we locked both pump and signal frequency to the frequency comb generated by a NIR fs mode-locked fibre laser, linked to the caesium primary standard. With this last configuration we carried out saturation spectroscopy of several transitions belonging to the ν1 rovibrational band of CH3I, resolving their electronic quadrupole hyperfine structure, and determining the absolute frequency of the hyperfine components with a 50-kHz-uncertainty. An upper limit for the idler linewidth has been estimated as 200 kHz FWHM.

$Research paper thumbnail of Experimental Comparison between the Index of Refraction in Strongly Driven and Degenerate Two-Level Systems$

Slow and Fast Light, 2008

Optoelectronic Integration on Silicon II, 2005

Fiber Bragg Gratings (FBG) sensors are a very promising solution for strain and/or temperature mo... more Fiber Bragg Gratings (FBG) sensors are a very promising solution for strain and/or temperature monitoring in hostile or hazardous environments. In particular, their typical immunity to EMI and the absence of electrical signals and cables, encourage the use of FBG sensors in aerospace structure. Moreover, FBG sensors can be embedded in composite materials, allowing the fabrication of the so-called smart-materials.