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.

Integrated optical switches using liquid crystal cells

Abstract: The design procedure is described of integrated optical switches to be fabricated by inserting a liquid-ciystal cell into a glass planar waveguide. Two configurations are analysed, corresponding to ON-OFF and OFF-ON operation, respectively. Preliminary experimental data on the waveguide characteristics and device fabrication process are also presented.

Reflective grating interferometer: a versatile and simple system for education in optics

Abstract: Recently has been developed a two component interferometer that has several advantages when used for eduction and training in optics. It is a wavefront division interferometer based on the use of a reflective grating that is used for recombination of two portion of one plane wavefront, obtained using a low cost parabolic mirror of commercial telescopes. The alignment operation is performed setting the mirror and the reflective grating at 90 degree each other. Interference fringe pattern are presented in all the volume in front the reflective grating interferometer and a screen or a CCD camera without lens can be used to visualize fringes. The interferometer being made of only two components is also very stable. Fringe pattern spacing and orientation can be simply changed rotating the mirror on a vertical axis or tilting it respectively. The fact that mirror and the grating are adjacent has some advantages on the pedagogical side because students can understand better how relative movements of the two components affect the changes in the fringe pattern. This interferometer is used not only to study interferometry but can be used also to study geometrical optics using the fringe pattern as a grid to perform Ronchi test. In such a way it is possible to conduct investigation on aberrations of optical components (Spherical, astigmatism and coma) or determine focal lengths lenses by using Moire effect. In conclusion the RGI is a system that comprises, at same time, in its operation different areas of the optics: interferometry, diffraction, wavefront picture of light, geometrical optics, testing. Examples of application for education purposes are described.

Seismic And Volcanic Risk Evaluation ByLarge Area Geo-monitoring Optical FibreSensor Networks: The SIMONA Project

Abstract: 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.

Integrated optical switches using liquid crystal cells

Abstract: The design procedure is described of integrated optical switches to be fabricated by inserting a liquid-crystal cell into a glass planar waveguide. Two configurations are analysed, corresponding to ON-OFF and OFF-ON operation, respectively. Preliminary experimental data on the waveguide characteristics and device fabrication process are also presented.

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.