Pietro Ferraro

Bio: Pietro Ferraro is an academic researcher from National Research Council. The author has contributed to research in topics: Digital holography & Holography. The author has an hindex of 61, co-authored 653 publications receiving 12666 citations. Previous affiliations of Pietro Ferraro include Aeritalia & Centre national de la recherche scientifique.

Non-Invasive Optical Detection of Submicron Domains in Lithium Niobate Crystals

Abstract: A non-invasive detection of shallow submicron-scale ferroelectric domains has been demonstrated by optical diffraction technique. Periodic sub-micron domains are of great interest to the field of optics and optoeletronics and non-destructive techniques for their accurate inspection are always desirable. Submicron-scale domains have been fabricated by electric field overpoling in lithium niobate substrates and successively inspected by visualizing the diffraction grating just after poling and destructive etching process. The results demonstrate the usefulness of the technique for a non-invasive and rapid inspection of submicron-scale domains otherwise not visible by the conventional non-destructive methods available nowadays.

Interferometric measurement of thermal expansion coefficients and thermo-optic coefficients in ferroelectric crystals

Abstract: We demonstrate a dual interferometric technique for simultaneous and independent measurements of the temperature dependence of the thermo-optic and thermal expansion coefficients in ferroelectric crystals. The crystal temperature can be changed from room temperature up to about 200°C by an actively stabilized heater (stability < 0.1°C). The thermal expansion coefficient is determined using a moire interferometer and monitoring the period of a grating written on the z-face of the crystal sample as a function of the temperature of the crystal. The thermo-optic coefficients of both ordinary and extraordinary axes are estimated by measuring the optical path variation measured by a Mach-Zehnder interferometer with one arm passing through the crystal perpendicularly to the crystal z-axis. This method can be applied to a wide variety of optical materials, when an accurate knowledge of the temperature dependence of the refractive index and thermal expansion is needed.

Peripheral blood mononuclear cells analysis in microfluidic flow by coherent imaging tools

Abstract: Cell of human blood stream are divided into two groups: Red Blood Cells (RBC) and White Blood Cells (WBC). RBC have a peculiar biconcave disk shape and they are responsible for the delivering of O 2 and CO 2 through the body. WBC are a more widespread class of cell ensuring immunity against pathogens. They can be divided in two main classes: granulocyte cells and A-granulocyte cells. Neutrophils, basophils and eosinophils belong to the granulocyte cell class, while lymphocytes and monocytes belong to A-granulocyte. Both in RBC and WBC, the intrinsic physical properties of a cell are indicators of cell condition and, furthermore, of the overall human body state. Thus, the accurate comprehension of the physiological structure of WBCs is fundamental to recognize diseases. Here we show the possibility to simple and straightforwardly characterize the physical properties of individual RBC and mononuclear WBC in a microfluidic context, using a wide angle light scattering apparatus and a corresponding theoretical simulation of Optical Signature (OS). A non-Newtonian polymer alignment solution for cell is used to ensure an individual cell alignment in the microfluidic flow, thus permitting a precise investigation. Additionally, Quantitative Phase Imaging (QPI) holographic measurements are performed to estimate cell morphometric features, such as their refractive index. We analyzed more than 200 WBCs and 100 RBCs of three different probands. Results showed distinct cell populations according to their measured dimensions and shape, which can be associated to the presence of RBC, lymphocytes and monocytes.

Optical-frequency-comb stabilised lasers for interrogation of fibre-resonator strain sensors

Abstract: Quasi-static and dynamic strain sensing is performed by means of a fibre Bragg-grating resonator based on an optical-frequency-comb stabilised laser. The comb synthesizer, centred around 1560 nm, is a fs-pulsed fibre laser, which is phase-locked to an ultra-stable quartz oscillator, serving as an optical reference to minimise laser-frequency and phase noise both in the long and short-term operation. Detection limits in the order of a few peRMS/√Hz, in the Hz and sub-Hz range, are demonstrated, while a sub- pe sensitivity is expected at higher frequencies in the acoustic range.

Looking beyond Smoke and Flames by Lensless Infrared Digital Holography

Abstract: To reveal what’s behind the flames is a key and challenging aim both in the industrial and, above all, in security field.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

Abstract: A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fiber grating sensors

Abstract: We review the recent developments in the area of optical fiber grating sensors, including quasi-distributed strain sensing using Bragg gratings, systems based on chirped gratings, intragrating sensing concepts, long period-based grating sensors, fiber grating laser-based systems, and interferometric sensor systems based on grating reflectors.