Franco Gori - Academia.edu (original) (raw)

Papers by Franco Gori

Fourth International Conference on Applications of Optics and Photonics, 2019

In this work, the paraxial evolution of fields generated by pseudo-Schell vortex sources is analy... more In this work, the paraxial evolution of fields generated by pseudo-Schell vortex sources is analyzed through some global parameters. In particular, it is shown that the kurtosis parameter of these fields presents a minimum at the beam waist and a maximum which value and position depends on the coherence characteristics of the source

Optica Acta: International Journal of Optics, 1975

ABSTRACT A recently proposed iterative method for super-resolution is studied with the aid of pro... more ABSTRACT A recently proposed iterative method for super-resolution is studied with the aid of prolate spheroidal wave functions. Perfect imagery is shown to be achieved in the limit of an infinite number of iterations. The case of a finite number of iterations is examined and possible extensions of the method are mentioned.

The coherence and polarization features of partially coherent fields radiated from transversely p... more The coherence and polarization features of partially coherent fields radiated from transversely periodic electromagnetic sources are investigated in the most general case. Sources of this type are produced, for instance, when a partially polarized plane wave impinges onto an optical element, such as a polarization grating or an anisotropic wedge, which modifies the polarization of the incident field in a periodic way. Experimental results are reported, pertinent to the use of a double-wedge pseudo-depolarizer.

$Research paper thumbnail of Number of Degrees of Freedom in Inverse Diffraction$

Optica Acta: International Journal of Optics, 1983

Optics Communications, 1984

When a polychromatic field propagates the transverse distribution of the power spectrum generally... more When a polychromatic field propagates the transverse distribution of the power spectrum generally changes from one plane to another. Conditions are found under which the spectrum distribution maintains the same shape in any cross-section. Examples of fields satisfying these conditions are given.

Fusion Engineering and Design, 1995

Springer texts in electrical engineering, 1993

Illuminate an object with laser light and look at it through a diffraction grating. You will see ... more Illuminate an object with laser light and look at it through a diffraction grating. You will see a set of mutually displaced copies of the object. If the lateral extent of the object is small enough, the various copies do not overlap. You can easily devise a method for selecting a single copy of the object. For example, you can replace your own optical system, i.e., your eye, by a converging lens and let the multiple images that were impressing your retina be produced on a screen. Then, a hole on the screen will suffice to isolate a single image. You can even dispense with the laser light and repeat the observation in a more domestic environment by looking at a distant street lamp through a piece of fine fabric. In this case, all of the object copies except the central one will appear iridescent, but the basic phenomena will be the same.

Journal of the Optical Society of America, Nov 24, 2015

Applied optics, 1991

A recently proposed method for determining the optical constants of absorbing materials starting ... more A recently proposed method for determining the optical constants of absorbing materials starting from reflectance measurements is analytically treated. The conditions for a nonambiguous determination of the optical constants are established. The values of the parameters satisfying these conditions are explicitly evaluated.

Journal of the Optical Society of America, Apr 18, 2012

Journal of the Optical Society of America, Jul 27, 2015

Journal of Modern Optics, 1998

Photonics

A new class of stationary electromagnetic sources radiating outward from the surface of an infini... more A new class of stationary electromagnetic sources radiating outward from the surface of an infinitely long cylinder is introduced via vectorial coherent mode representation. First, two particular types of such sources are discussed: with either an electric or magnetic field aligned with the cylinder’s axis. The former case represents a scalar scenario, while the latter leads to the two-component electric field. The combination of these two types of sources is then considered by forming the three-component electric field vector. An extension to the stationary case is then made in which the electric field correlations are shown to be described by the intrinsically 3×3 cross-spectral density matrix. Several known theories of electromagnetic coherence and polarization are then invoked for the analysis of radiation, on and off the source surface. The results for the spectral density, degree of coherence, and degree of polarization are then discussed in detail. The effects of mutual corre...

Optics Letters, Jun 28, 2022

Optics Letters

The on-axis cross-spectral density (CSD) of a beam radiated by a stationary source with a circula... more The on-axis cross-spectral density (CSD) of a beam radiated by a stationary source with a circular coherence state and a Gaussian spectral density is obtained in the closed form. It is revealed that the on-axis CSD is expressed via the Laplace transform of the source’s degree of coherence or the Hilbert transform of the corresponding pseudo-mode weighting function. Such relations enable efficient tailoring of the on-axis spectral density, as we show with a slew of numerical examples.

Optics Letters, 2012

We show that the cross-spectral density in the far zone of a homogeneous spherical source can be ... more We show that the cross-spectral density in the far zone of a homogeneous spherical source can be described as a low-pass filtered version of that existing across the source surface. We prove that, to an excellent approximation, the corresponding filter with respect to a (normalized) spatial frequency ξ has a functional structure of the form √(1-ξ2), for 0≤ξ≤1. The cases of spatially incoherent and Lambertian sources are treated as significant examples.

Optics Letters, 2021

A new, to the best of our knowledge, class of partially coherent sources is introduced on the bas... more A new, to the best of our knowledge, class of partially coherent sources is introduced on the basis of the Christoffel–Darboux (CD) formula read as the expression of a possible cross-spectral density. It will be seen that such an interpretation is possible because the CD formula gives the reproducing kernel of a suitable Hilbert space. After discussing general properties of CD kernels, a specific example is worked out using Hermite polynomials. A connection with the density matrix will be highlighted.

Journal of the Optical Society of America A, 2021

An introduction to the Hilbert spaces that are endowed with a reproducing kernel is presented on ... more An introduction to the Hilbert spaces that are endowed with a reproducing kernel is presented on using the mathematical tools of Fourier optics and coherence theory. After giving the basic definition of such spaces, some examples are worked out to show how the inner product can take different forms depending on the particular function space one works with. The basic rule to build a reproducing kernel Hilbert space (RKHS) is then presented together with the basic properties of those spaces. Eigenfunctions and eigenvalues of the reproducing kernel are then illustrated and lead to the important integral representation of the reproducing kernel. The latter is used to present pseudomodal expansions and generalized forms of sampling. The concluding section offers some thoughts on the applications of RKHSs in wave optics. An appendix presents an introduction to treatments using more advanced concepts of functional analysis.

En este trabajo se propone el uso de diversos tipos de haces no-uniformemente y total-mente polar... more En este trabajo se propone el uso de diversos tipos de haces no-uniformemente y total-mente polarizados en medidas polarimétricas de muestras homogéneas y transparentes. Como ejemplos concretos de este tipo de haces se proponen los haces espiralmente pola-rizados y haces a la salida de medios uniáxicos anisótropos con el eje óptico en la direc-ción de propagación. Dichos haces se representan mediante modelos analíticos sencillos, teniendo en cuenta el carácter vectorial de los mismos, los cuales permiten conocer el campo en cualquier plano en propagación libre y a través de medios o sistemas que pue-den ser descritos mediante matrices de Müller. Mediante el uso de haces no-uniformemente y totalmente polarizados se simplifica notablemente el proceso de medi-da, siendo suficientes una o dos medidas según el haz utilizado, para la obtención de to-dos los elementos de la matriz de Müller de la muestra. Palabras clave: Polarización, polarimetría, haces no-uniformemente polarizados y cara...