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.

Compensation of aberrations in holographic microscopes: main strategies and applications

Abstract: Abstract Digital holography is a technique that provides a non-invasive, label-free, quantitative, and high-resolution imaging employable in biological and science of matter fields, but not only. In the last decade, digital holography (DH) has undergone very significant signs of progress that made it one of the most powerful metrology tools. However, one of the most important issues to be afforded and solved for obtaining quantitative phase information about the analyzed specimen is related to phase aberrations. Sources of aberrations can be diverse, and several strategies have been developed and tested to make DH a reliable optical system with submicron resolution. This paper reviews the most effective and robust methods to remove or compensate phase aberrations in retrieved quantitative phase imaging by DH. Different strategies are presented and discussed in detail on how to remove or compensate for such disturbing aberrations. Among the various methods improvements in the optical setups are considered the numerical algorithms, the hybrid methods, and the very recent Artificial Intelligence (AI) approaches to compensate for all aberrations which affect the setups to improve the imaging quality and the accuracy of the reconstruction images’ procedures.

Double-face and submicron two-dimensional domain patterning in congruent lithium niobate

Abstract: We report on the simultaneous fabrication of two-dimensional submicron engineered domain patterns on both crystal faces, in congruent lithium niobate. The fabrication technique is based on interference photolithography, which allows short pitch over large areas, followed by electric field poling performed in overpoling regime. Experimental results for different domain pattern geometries, on the two crystal faces, are reported. These structures could be useful for short-wavelength frequency conversion and Bragg gratings applications. The moireacute effect is used in the lithographic process to fabricate more complex structures which could find application in photonic bandgap devices

Plasmon resonance of gold nanorods for all-optical drawing of liquid droplets

Abstract: We present a laser-assisted system for dispensing liquid micro-droplets by near infrared illumination of a pyroelectric crystal functionalized with gold nanorods embedded into polyvinyl alcohol. The non-invasive near infrared source resonates with the plasmon oscillations of the gold nanorods, providing a controlled thermal stimulus able to generate the pyroelectric effect. The resulting electric field interacts electro-hydrodynamically with a liquid reservoir leading to precise drawing of micro-litre droplets. This laser-assisted electro-hydrodynamic technique may open the way to the development of more compact and non-invasive nano-dispensing devices.

Nanomechanics of a fibroblast suspended using point-like anchors reveal cytoskeleton formation

Abstract: In an attempt to better elucidate the material–cytoskeleton crosstalk during the initial stage of cell adhesion, here we report how suspended cells anchored to point-like bonds are able to assemble their cytoskeleton when subjected to mechanical stress. The combination of holographic optical tweezers and digital holography gives the cell footholds for adhesion and mechanical stimulation, and at the same time, acts as a label-free, force-revealing system over time, detecting the cell nanomechanical response in the pN range. To confirm the formation of the cytoskeleton structures after the stimulation, a fluorescence imaging system was added as a control. The strategy here proposed portends broad applicability to investigate the correlation between the forces applied to cells and their cytoskeleton assembly process in this or other complex configurations with multiple anchor points.

Adaptive and automatic diffraction order filtering by singular value decomposition in off-axis digital holographic microscopy.

Abstract: Digital holography is widely used in many fields for imaging, display, and metrology by exploiting its capability to furnish quantitative phase contrast maps. The entire processing pipeline that permits achievement of phase contrast images can be obtained by a cascade of numerical processing, such as zero-order and twin-image suppression, automatic refocusing, phase extraction by aberration compensation, and, if necessary, phase unwrapping. In this paper, we propose a new method, to the best of our knowledge, based on singular value decomposition filtering, to suppress zero-order and twin images in off-axis configuration, thus, automatically selecting the desired real diffraction order. We demonstrate the proposed approach in the case of lack of knowledge about the reference beam's frequency and curvature, which typically occurs in portable off-axis holographic microscope systems for lab-on-a-chip applications. We validate the proposed strategy by a comparison with common Fourier spatial filtering in the case of different experimental conditions and for several biological samples.

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.