Giovanni Pierattini

Bio: Giovanni Pierattini is an academic researcher from ARCO. The author has contributed to research in topics: Digital holography & Holography. The author has an hindex of 25, co-authored 128 publications receiving 3222 citations. Previous affiliations of Giovanni Pierattini include Olivetti.

Self-Transparency Effect in a Two-Component Heterogeneous Polymeric Blend

Abstract: A general approach to the light-induced anisotropy (LIA) effects in initially isotropic media subjected to a biharmonic laser field (pump-probe), that is based on a tensor operator formalism, is presented. Using such a theoretical treatment, we propose novel nonlinear spectroscopic techniques. We show new results dealing with advantageous measurement of the 3rd-order nondegenerate nonlinear susceptibility (3NNS), including the 3NNS phase (3NNSP) and the real and imaginary parts of the effective 3NNS. Figure 1 is the schematic illustration of a method for measuring 3NNSP in the framework of optically heterodyned polarization spectroscopy (OHPS) when the components of 3NNS are connected by the Kleinman relationships. In the standard OHPS arrangement with the slightly tilted analyzer and the linearly polarized probe beam at 45 to the major axis of the pump polarization ellipse, under tuning of the pump intensity W) or ellipticity (tans) we can find the minimum OHPS signal (AI which is determined by 3NNSP. Another possibility for measuring 3NNSP occurs when the linearly polarized pump and circularly polarized probe beams are used. In this case, the tangent of double azimuth of the output probe polarization is exactly equal to 3NNSP. The validity of the theoretical treatment presented is supported by the experimental data. Furthermore, we point out that some previous theoretical studies devoted to the similar problems are not quite correct and should be revised. In Fig. 2 the nonlinear polarization spectroscopy signal normalized to the maximum value is plotted as a function of c. The line 1 is fitted with experimental data for malachite green in water.1 The experimental results for crystal violet, methylene-blue and rhodamine-B in aqueous solutions are shown by circles, triangles and squares, respectively. They are in rather good agreement with our experimental curve 2.

Nonlinearity at an Interface

Abstract: Nonlinearity interfaces, i.e. those between an ordinary dielectric and a dielectric material with an intensity-dependent index of refraction, have recently played an important role as an element in optical bistable devices 1,3. The efforts of researchers are aimed at finding non linear materials with particular optical properties in order to fit very stringent requirements. A very interesting nonlinear optical material is “latex” which consists of an aqueous polystyrene microspheres suspension4.

Investigation of silion MEMS structures subjected to thermal loading by digital holography

Abstract: In this paper we study silicon MEMS (Microelectromechanical systems) structures subjected to thermal loading. Digital holography has been investigated as inspection tool to evaluate the deformation induced by the thermal loading. Application of DH on structures with several different geometries and shapes, like cantilever beams, bridges and membranes is reported and result will be discussed. Dimensions of the inspected microstructures, varies in the range 1÷50μm. The experimental results shown that a "bimorph-effect" induces a deformation in MEMS structures. The difficulties encountered in performing the deformation analysis by digital holography in real-time will be afforded and discussed. A method with automatic focus tracking in Digital Holography is proposed allowing inspection of MEMS, under thermal loading, in real-time.

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.

Femtosecond laser micromachining in transparent materials

Abstract: Femtosecond laser micromachining can be used either to remove materials or to change a material's properties, and can be applied to both absorptive and transparent substances. Over the past decade, this technique has been used in a broad range of applications, from waveguide fabrication to cell ablation. This review describes the physical mechanisms and the main experimental parameters involved in the femtosecond laser micromachining of transparent materials, and important emerging applications of the technology. Interactions between laser and matter are fascinating and have found a wide range of applications. This article gives an overview of the fundamental physical mechanisms in the processing of transparent materials using ultrafast lasers, as well as important emerging applications of the technology.

Digital recording and numerical reconstruction of holograms

Abstract: This article describes the principles and major applications of digital recording and numerical reconstruction of holograms (digital holography). Digital holography became feasible since charged coupled devices (CCDs) with suitable numbers and sizes of pixels and computers with sufficient speed became available. The Fresnel or Fourier holograms are recorded directly by the CCD and stored digitally. No film material involving wet-chemical or other processing is necessary. The reconstruction of the wavefield, which is done optically by illumination of a hologram, is performed by numerical methods. The numerical reconstruction process is based on the Fresnel–Kirchhoff integral, which describes the diffraction of the reconstructing wave at the micro-structure of the hologram. In the numerical reconstruction process not only the intensity, but also the phase distribution of the stored wavefield can be computed from the digital hologram. This offers new possibilities for a variety of applications. Digital holography is applied to measure shape and surface deformation of opaque bodies and refractive index fields within transparent media. Further applications are imaging and microscopy, where it is advantageous to refocus the area under investigation by numerical methods.

Principles and techniques of digital holographic microscopy

Abstract: Digital holography is an emerging field of new paradigm in general imaging applications. We present a review of a subset of the research and development activities in digital holography, with emphasis on microscopy techniques and applications. First, the basic results from the general theory of holography, based on the scalar diffraction theory, are summarized, and a general description of the digital holographic microscopy process is given, including quantitative phase microscopy. Several numerical diffraction methods are described and compared, and a number of representative configurations used in digital holography are described, including off-axis Fresnel, Fourier, image plane, in-line, Gabor, and phase-shifting digital holographies. Then we survey numerical techniques that give rise to unique capabilities of digital holography, including suppression of dc and twin image terms, pixel resolution control, optical phase unwrapping, aberration compensation, and others. A survey is also given of representative application areas, including biomedical microscopy, particle field holography, micrometrology, and holographic tomography, as well as some of the special techniques, such as holography of total internal reflection, optical scanning holography, digital interference holography, and heterodyne holography. The review is intended for students and new researchers interested in developing new techniques and exploring new applications of digital holography.