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.

Deep Learning-Based, Misalignment Resilient, Real-Time Fourier Ptychographic Microscopy Reconstruction of Biological Tissue Slides

Abstract: Fourier ptychographic microscopy probes label-free samples from multiple angles and achieves super resolution phase-contrast imaging according to a synthetic aperture principle. Thus, it is particularly suitable for high-resolution imaging of tissue slides over a wide field of view. Recently, in order to make the optical setup robust against misalignments-induced artefacts, numerical multi-look has been added to the conventional phase retrieval process, thus allowing the elimination of related phase errors but at the cost of a long computational time. Here we train a generative adversarial network to emulate the process of complex amplitude estimation. Once trained, the network can accurately reconstruct in real-time Fourier ptychographic images acquired using a severely misaligned setup. We benchmarked the network by reconstructing images of animal neural tissue slides. Above all, we show that important morphometric information, relevant for diagnosis on neural tissues, are retrieved using the network output. These are in very good agreement with the parameters calculated from the ground-truth, thus speeding up significantly the quantitative phase-contrast analysis of tissue samples.

Direct quantitative imaging of the writing stage in a photosensitive azopolymer by digital holography

Abstract: In this paper, we demonstrated that the gradual formation of a surface relief grating (SRG) in azopolymer thin films under continuous light exposure could be directly observed in situ and in real-time, allowing full-field characterization with high spatial resolution. We reported here for the first time, to the best of our knowledge, that digital holography (DH) can be adopted for investigating and monitoring an inscribed holographic surface relief grating (SRG) of azopolymers by two-beam laser interference lithography over a wide area. The writing process could be assessed through quantitative phase imaging (QPI). The reported results show that the proposed method is a truly valuable diagnostic tool that can be useful for investigating the spatial distribution of the writing process, which can eventually contribute to shedding light on the still unclear origin and related mechanism of SRG formation in azopolymers.

On the Complex and Reversible Pathways of CdSe Quantum Dots Driven by Pyroelectric-Dielectrophoresis

Abstract: Electrophoresis (EP) and dielectrophoresis (DEP) are the two well-established methodologies to manipulate nanoparticles (NPs). Recently, DEP by a virtual electrode platform was demonstrated on ferroelectric substrates, where the driving force is due to the strong electric field generated by the pyroelectric effect, thus opening new scenarios for manipulating the matter. Such an innovative approach named pyroelectric-DEP has several advantages over traditional EP and DEP. However, a detailed study on this novel approach is required for understanding the complex pathways traced by NPs under the action of the pyroelectric-driven forces and thus for explaining the final patterns. Here, we investigate experimentally the dynamic behavior of CdSe NPs through time-lapse fluorescence microscopy imaging. Complete visualization and measurement of the directed-assembling process of NPs immersed in polydimethylsiloxane fluid is reported, which shows some unpredicted results with respect to the previous works, thus opening the route for designing in principle a reversible and switchable device allowing two different and reversible final NP-patterned states. The observed phenomena are fully analyzed by experimental and simulated analysis, and the movements of NPs is performed to elucidate in depth the involved processes. The investigation furnishes an interesting result that the complex behavior of the NPs can be fully comprehended and explained by considering the superposition of both EP and DEP forces.

Plastic lab-on-chip for the optical manipulation of single cells

Abstract: Lab-on-chips (LoCs) are microsystems capable of manipulating small amounts of fluids in microfluidic channels. They have a huge application potential, from basic science to chemical synthesis and point-of-care medical analysis. Polymers are rapidly emerging as the substrate of choice for LoC production, thanks to a low material cost and ease of processing. Two breakthroughs that could promote LoC diffusion are a microfabrication technology with cost-effective and rapid prototyping capabilities and also an integrated on-chip optical detection system. This chapter proposes the use of femtosecond laser micromachining combined with microinjection moulding as a novel highly-flexible microfabrication platform for polymeric LoCs with integrated optical detection, for the realization of low-cost and truly portable biophotonic microsystems. We demonstrate a LoC for the relevant application of non-invasive and contactless mechanical phenotyping of single cancer cells.

Fabrication of 2D sub-micron structures in lithium niobate for photonic crystal applications

Abstract: We report on the fabrication and characterization of the first periodic sub-micron scale one- and two-dimensional surface structures in congruent 500 μm thick lithium niobate crystal samples. Structures with periods from 2 μm down to 500 nm, lateral feature sizes down to 200 nm and depths around 10 μm, largely compatible with conventional waveguide fabrication, have been obtained. Such structures are fabricated by selective wet etching of ferroelectric domain engineered samples obtained by electric field poling performed at an overpoling regime. Holographic lithography is here used to obtain sub-micron periodic insulating gratings to be used for selective ferroelectric domain reversal. The short-pitch fabricated structures are attractive in a wide range of applications, such as nonlinear short-wavelength conversion processes, backward second-harmonic generation, fabrication of novel tunable photonic crystal (PC) devices, electro-optically modulated Bragg gratings. Moreover moire beating effect is used in the photolithographic process to fabricate even more complex structures which could find applications in complicated photonic bandgap devices involving for example micro-ring resonators. In order to investigate the possibility to utilize these structures for PC applications, accurate and complete topographic characterization has been performed by using different techniques. Atomic force microscope provides high-resolution information about the lateral and depth feature size of the structures. Interferometric techniques, based on digital holography, have been used for wide field information about the homogeneity and periodicity of the structures.

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.