Showing papers by "José A. Ferrari published in 2003"
TL;DR: It is demonstrated that spiral fields generate nondiffracting dark beams using a collimated laser beam incident on a compact disc as a mask for the generation of spiral fields.
Abstract: In this paper we demonstrate that spiral fields generate nondiffracting dark beams. A collimated laser beam incident on a compact disc, i.e., a commercial CD, was used as mask for the generation of spiral fields. We study theoretically and experimentally the intensity distribution near the axis of the optical system.
9 citations
TL;DR: In this article, the same effect could be obtained without the use of a photorefractive crystal by simple rotation of the analyzer, without the need to use a single crystal.
Abstract: In a recent paper (Opt. Laser Technol. 34 (2002) 605) Anand and Narayanamurthy described a method for measurement of Faraday rotations using a photorefractive Bi 12 TiO 20 . The effects they observed have nothing to do with the source intensity nor with the photorefractive nature of the crystal. The same effect could be obtained without the use of a photorefractive crystal by simple rotation of the analyzer.
3 citations
TL;DR: A novel interferometric setup in which the reference and test waves are circularly polarized orthogonally to each other, creating a polarization grating that is distorted by the phase of the test object.
Abstract: Interferometry is a technique for reconstructing the profiles of phase objects. We present a novel interferometric setup for generating interferograms with doubled phase profile and enhanced contrast compared with the standard interferogram. The proposed system consists of a two-beam interferometer in which the reference and test waves are circularly polarized orthogonally to each other. They are superposed upon a bacteriorhodopsin film, creating a polarization grating that is distorted by the phase of the test object. This polarization pattern is read by a polarized He-Ne beam. We show analytically and experimentally that, when the zero diffraction order is removed, an interferogram with doubled phase profile and enhanced contrast is obtained.
3 citations
TL;DR: This method for the compensation of gain unbalance in optical sensors with separate light path that involve two separate detection and conditioning electronic devices can be applied electric power and current sensors that use Faraday and Pockels cells to measure current and voltage, respectively.
Abstract: We describe a method for the compensation of gain unbalance in optical sensors with separate light paths that involve two separate detection and conditioning electronic devices. The method is based on the digital measurement of harmonics of the output intensities from each path by means of the fast Fourier transform algorithm. The quotient of the amplitude of harmonics allows us to calculate the unbalance between paths and to compensate for it. In particular, this method can be applied in electric power and current sensors that use Faraday and Pockels cells to measure current and voltage, respectively.
3 citations