Maria L. Calvo - Academia.edu (original) (raw)

Papers by Maria L. Calvo

$Research paper thumbnail of Introducing m-learning in the classroom: a proposal for diffraction and image processing training$

Asian Journal of Physics

Dedicated to Prof Maria J Yzuel We present results obtained with teaching and learning technique,... more Dedicated to Prof Maria J Yzuel We present results obtained with teaching and learning technique, the so called m-Learning (or mobile-Learning). This is a proposal with the aim to introduce an easy procedure to teach how to treat acquired images digitally, and to be detected and analyzed by undergraduate students, of the branch of physics and optics. The results indicated that m-learning could be compatible with diffraction phenomena training in the classroom.

$Research paper thumbnail of Image reconstruction from amplitude-only and phase-only data in the fractional Fourier domain$

Optics and Spectroscopy, 2003

Image reconstruction from amplitude-only and phase-only data in the fractional Fourier domain app... more Image reconstruction from amplitude-only and phase-only data in the fractional Fourier domain applying the inverse fractional Fourier transform is analyzed on the examples of perfect edges of different contrasts and real-world image.

Transatlántica de …, 2007

LA óPTICA ES LA DISCIPLINA CIENTíFICA DEDICADA A la generación, transmisión, detección, control y... more LA óPTICA ES LA DISCIPLINA CIENTíFICA DEDICADA A la generación, transmisión, detección, control y manipulación de luz. Como es bien conocido, de acuerdo con la formulación de la Física Cuántica a principios del siglo XX, en su nivel más elemental la ...

Mathematical Optics, 2012

Phosphorus, Sulfur, and Silicon and the Related Elements, 2018

GRAPHICAL ABSTRACT ABSTRACT We outline some general properties of slow neutrons and their interac... more GRAPHICAL ABSTRACT ABSTRACT We outline some general properties of slow neutrons and their interactions in material media, their use in Boron Neutron Capture Therapy (BNCT) and their waveguiding properties. We review two important experiments on slow neutron confined propagation: in thin films and in polycapillary glass fibres. Based upon the first experiment and on previous proposals, we formulate two new proposals regarding possibilities for improved focalization (at and a bit below one micron) and propagation along longer lengths (up to about 1 m) with relatively small attenuation, and discuss possible implications for BNCT of small tumours. We emphasize the general interest and possible applications of exploring short scales by means of slow neutrons, through suitable combinations of the devices involved in those two experiments.

Journal of Physics D: Applied Physics, 1989

$Research paper thumbnail of A photopolymerizable glass with diffraction efficiency near 100% for holographic storage$

Applied Physics Letters, 2001

Permanent holographic storage has been demonstrated in a photopolymerizable organically modified ... more Permanent holographic storage has been demonstrated in a photopolymerizable organically modified silica glass. The glass was prepared by dispersing a titanocene photoinitiator and a high refractive index acrylic monomer in a porous silica matrix. This glass exhibits unprecedented sensitivity and refractive index change upon a moderate exposure to green light and can be fabricated in thickness up to several millimeters. A photopolymerizable storage medium of such a thickness with good holographic properties is needed for practical holographic storage devices. Lack of such medium has been considered the main obstacle in development of write-once holographic memories. In our glass, we have stored permanent volume holograms of diffraction efficiency approaching 100% and refractive index modulation up to 4.5×10−3, making this photopolymerizable material suitable for use in holographic data storage.

$Research paper thumbnail of Photopolymerizable glasses incorporating high refractive index species and ionic liquid: A comparative study$

Journal of Applied Physics, 2011

Three different holographic photomaterials belonging to the class of photopolymerizable glasses h... more Three different holographic photomaterials belonging to the class of photopolymerizable glasses have been synthesized using sol-gel techniques, and characterized with the purpose of a comparative study. Their behavior is analyzed in terms of achieved refractive index modulation, dark diffusion mechanism, diffraction efficiency and optical quality; in order to determine their suitability for different holographic applications.

Optics Letters, 2012

The design and fabrication of an ultracompact silicon-on-insulator polarization converter is repo... more The design and fabrication of an ultracompact silicon-on-insulator polarization converter is reported. The polarization conversion with an extinction ratio of 16 dB is achieved for a conversion length of only 10 μm. Polarization rotation is achieved by inducing a vertical asymmetry by forming in the waveguide core two subwavelength trenches of different depths. By taking advantage of the calibrated reactive ion etch lag, the two depths are implemented using a single mask and etching process. The measured converter loss is −0.7 dB and the 3 dB bandwidth is 26 nm.

$Research paper thumbnail of Importance of the phase and amplitude in the fractional Fourier domain$

Journal of the Optical Society of America A, 2003

The importance of the amplitude and phase in the fractional Fourier transform (FT) domain is anal... more The importance of the amplitude and phase in the fractional Fourier transform (FT) domain is analyzed on the basis of the rectangular signal and the real-world image. The quality of signal restoration from only the amplitude or from only the phase of its fractional FT by applying the inverse fractional FT is considered. It is shown that the signal reconstructed from the amplitude of the fractional FT usually reveals the main features of the original signal only for relatively low fractional orders. On the basis of phase information in the fractional FT domains, significant details of the signal can be obtained for nearly all fractional orders.

Applied Optics, 1984

In this paper we present a theoretical model for the transmission function of a biological cell. ... more In this paper we present a theoretical model for the transmission function of a biological cell. Three different cases are considered: real transmission function, pure phase object, general case, where both real and complex terms are present in the transmission function. In all cases we studied the response in the Fourier plane. Comparison of the proposed models leads us to conclude that the most correct treatment would come from the general case, where it was found that the membrane contribution predominates in the total diffracted amplitude distribution.

Journal of the Optical Society of America A, 2010

A q-plate is a stratified medium composed of a uniaxial nematic liquid crystal with an inhomogene... more A q-plate is a stratified medium composed of a uniaxial nematic liquid crystal with an inhomogeneous orientation of the optical axis possessing a topological charge q , which looks promising as a switching device. This work reports an approach to diagonalizing the dielectric tensor in q-plates, giving a detailed study of nontrivial tensor coordinate transformations. The relationship between the diagonal dielectric tensor and the topological charge of the plate is established. From that, the dielectric tensor for a given q-plate can be explicitly calculated in a convenient frame, and hence the field propagation equations can be derived. These studies establish a theoretical basis that could further deepen the research on these particular structures for nonconventional manipulation of the light.

AIP Conference Proceedings, 2007

We introduce the gyrator transform which produces a rotation of two-dimensional signal in phase s... more We introduce the gyrator transform which produces a rotation of two-dimensional signal in phase space. Main properties of this transform are considered. The flexible optical set up for gyrator transform experimental implementation is discussed. The applications of the gyrator transform to image processing such as filtering, noise reduction, encryption are demonstrated..

Optics Letters, 2013

We report a spatial heterodyne Fourier-transform spectrometer implemented with an array of optica... more We report a spatial heterodyne Fourier-transform spectrometer implemented with an array of optical fiber interferometers. This configuration generates a wavelength-dependent stationary interferogram from which the input spectrum is retrieved in a single shot without scanning elements. Furthermore, fabrication and experimental deviations from the ideal behavior of the device are corrected by spectral inversion algorithms. The spectral resolution of our system can be readily scaled up by incorporating longer optical fiber delays, providing a pathway toward surpassing current spectroscopy resolution limits.

$Research paper thumbnail of Focusing properties of fractal zone plates: experimental implementation with a liquid-crystal display$

Optics Letters, 2004

We report the first experimental results, to our knowledge, with fractal zone plates implemented ... more We report the first experimental results, to our knowledge, with fractal zone plates implemented in a liquidcrystal display. Our results largely agree with theory for the axial irradiance distribution of these lenses. The dependence of the shape and size of the focus points on critical design parameters is discussed. Additional unpredicted features are also described.

Optics and Spectroscopy, 2008

The effect of the Gaussian beam width on the focusing properties of the chainlike Gaussian beam f... more The effect of the Gaussian beam width on the focusing properties of the chainlike Gaussian beam formed upon diffraction of laser radiation on a binary amplitude mask is studied. It is found that a decrease in the Gaussian beam width increases the sizes of focal spots and the focus depth, decreases the intensity in the focuses, and does not affect the focus position.