Person:
Calvo Padilla, María Luisa

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First Name
María Luisa
Last Name
Calvo Padilla
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Department
Area
Optica
Identifiers
UCM identifierDialnet ID

Search Results

Now showing 1 - 10 of 86
  • Publication
    Introduction to gyrator transform
    (American Institute of Physics (AIP), 2007) Alieva, Tatiana Krasheninnikova; Rodrigo Martín-Romo, José Augusto; Calvo Padilla, María Luisa
    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.
  • Publication
    Edge image quality assessment: a new formulation for degraded edge imaging
    (Elsevier Science BV, 1998-12) Manzanares Ituarte, Ana; Calvo Padilla, María Luisa; Chevalier dl Río, Margarita; Lakshminarayanan, Vasudevan
    We discuss a formalism to characterize degraded edge images formed in a diffraction limited system (with circular pupil of unit radius) under conditions of incoherent illumination. We introduce a novel definition of degraded edges and consider this approach to model a basic optical mechanism involved in the perception of visual depth and edge detection. We introduce a degradation parameter to quantize the degree of edge blur. We present a generalization of such a procedure by assuming the Heaviside function to be a systematic generator of degraded edges. We reproduce experimentally the predictions made by the formalism proposed herein.
  • Publication
    Photopolymerizable sol-gel nanocomposites for holographic recording
    (IOP Publishing Ltd., 2009-02) Calvo Padilla, María Luisa; Cheben, Pavel
    The research into new photosensitive materials with advanced performance for holographic applications is an active branch in material science and photonics, still challenging the field. We proposed a new class of volume hologram recording materials, sol-gel nanocomposites, with important advantages for various holographic applications, including data storage. Here we review several aspects of different types of photosensitive sol-gel glasses that we have developed. Our photopolymerizable glasses exhibit high refractive index modulation, diffraction efficiencies close to the theoretical maxima, along with low scattering and negligible shrinkage. Beside these and other practical advantages discussed in this paper, our recently developed nanocomposite glass incorporating high refractive index species has enabled fundamental studies of new optical phenomena such as the Pendellosung effect, which was observed for the first time in the optical band.
  • Publication
    Wave-front conversion between a Gaussian beam with a cylindrical phase function and a plane wave in a monomode on-axis transmission holographic coupler
    (Optical Society of America, 1993-12) Cheben, Pavel; Calvo Padilla, María Luisa
    We present a coupled-wave-analysis-based treatment for a wave-front conversion problem between a Gaussian beam with a cylindrical phase and a plane wave for a two-dimensional on-axis geometry. A coupled-wave approach to the multiple-scattering process in an inhomogeneous dielectric medium offers a clear physically interpretable description of the diffraction phenomena in volume media as well as the possibility of an intelligible mathematical treatment. An analytical integral solution for the amplitudes of the two modes of diffraction is submitted. High diffraction efficiency (≈1) and the deterioration of reconstruction fidelity are predicted. It is of interest to apply the model to the analysis and design of a monomode holographic fiber-to-fiber coupler, wave-front correctors, and holographic interconnection devices.
  • Publication
    m-Learning and holography: compatible techniques?
    (Society of Photo-optical Instrumentation Engineers, 2014) Calvo Padilla, María Luisa
    Since the last decades, cell phones have become increasingly popular and are nowadays ubiquitous. New generations of cell phones are now equipped with text messaging, internet, and camera features. They are now making their way into the classroom. This is creating a new teaching and learning technique, the so called m-Learning (or mobile-Learning). Because of the many benefits that cell phones offer, teachers could easily use them as a teaching and learning tool. However, an additional work from the teachers for introducing their students into the m-Learning in the classroom needs to be defined and developed. As an example, optical techniques, based upon interference and diffraction phenomena, such as holography, appear to be convenient topics for m-Learning. They can be approached with simple examples and experiments within the cell phones performances and classroom accessibility. We will present some results carried out at the Faculty of Physical Sciences in UCM to obtain very simple holographic recordings via cell phones. The activities were carried out inside the course on Optical Coherence and Laser, offered to students in the fourth course of the Grade in Physical Sciences. Some open conclusions and proposals will be presented.
  • Publication
    Fresnel diffraction effects in Fourier-transform arrayed waveguide grating spectrometer
    (The Optical Society Of America, 2007-12-10) Rodrigo Martín-Romo, José Augusto; Cheben, Pavel; Alieva, Tatiana Krasheninnikova; Calvo Padilla, María Luisa; Scott, Alan; Solheim, Brian; Xu, Dan-Xia; Delâge, André
    We present an analysis of Fourier-transform arrayed waveguide gratings in the Fresnel diffraction regime. We report a distinct spatial modulation of the interference pattern referred to as the Moire-Talbot effect. The effect and its influence in a FT AWG device is explained by deriving an original analytical expression for the modulated field, and is also confirmed by numerical simulations using the angular spectrum method to solve the Fresnel diffraction integral. We illustrate the retrieval of spectral information in a waveguide Fourier-transform spectrometer in the presence of the Moire-Talbot effect. The simulated device comprises two interleaved waveguide arrays each with 180 waveguides and the interference order of 40. It is designed with a Rayleigh spectral resolution of 0.1 nm and 8 nm bandwidth at wavelength λ~1.5 µm. We also demonstrate by numerical simulations that the spectrometer crosstalk is reduced from -20 dB to -40 dB by Gaussian apodization.
  • Publication
    Fourier series analysis of fractal lenses: theory and experiments with a liquid-crystal display
    (The Optical Society Of America, 2006-02-20) Davis, Jeffrey A.; Sigarlaki, Sean Paul; Craven, Julia M.; Calvo Padilla, María Luisa
    We report on a Fourier series approach that predicts the focal points and intensities produced by fractal zone plate lenses. This approach allows us to separate the effects of the fractal order from those of the lens aperture. We implement these fractal lenses onto a liquid-crystal display and show experimental verification of our theory.
  • Publication
    Teorías de la difracción de ondas electromagnéticas por redes de volumen: Una revisión
    (Sociedad Mexicana de Física, 1998-08) Cheben, Pavel; Calvo Padilla, María Luisa
    Se presenta una revisión de las teorías de la difracción de ondas electromagnéticas por redes de volumen. En el enfoque de este trabajo se encuentran las teorías de los siguiente grupos: teorías de ondas acopladaseorías modales, teorías de dispersión múltiple y teorías electromagnéticas, siempre y cuando sean apropiadas para el análisis de redes de volumen. Se incluye también una revisión de teorías y métodos con menor impacto en el campo estudiado, tales como teorías de medio efectivo, método de difracción por el entorno, método de elementos finitos o algoritmos microgenéticos. Se recogen un tofal de 225 publicaciones seleccionadas que abarcan un período de aproximadamente cien años: 1891-1997.
  • Publication
    A novel wavelength dispersive device with a dispersive element based on staircase-like straight and parallel arrayed waveguides
    (Elsevier Science BV, 2007-02-01) Martínez Matos, Óscar; Calvo Padilla, María Luisa; Cheben, Pavel; Rodrigo Martín-Romo, José Augusto; Janz, Siegfried; Xu, Dan-Xia; Delâge, André
    We propose a new type of arrayed waveguide grating (AWG) multiplexer/demultiplexer based on modified group refractive index. This device is composed by an array of straight and parallel waveguides of equal length and each waveguide consist of two sections with different width. The length of the two sections are changed from a waveguide to the adjacent one following a linear dependence resulting in a wavelength dispersive waveguide array. An example of the device design for silicon-on-insulator (Sol) platform is provided and numerical simulations have been carried out for various arrayed waveguide parameters. We demonstrate that the group index modification can be used for tailoring device dispersion properties, and that it can also result in new dispersion characteristics predicted numerically not observed in conventional AWGs. Additional advantages are that the demultiplexer does not necessarily require bending waveguide sections as in a conventional AWG (de)multiplexers, and thus yields highly compact devices with potentially very low insertion loss. Channel spacing of I nm have been predicted for sub-micron waveguides sizes. In this paper it is also proposed a novel wavefront converter based on waveguide array lens-like element with waveguides broadened sections. Numerical results for different input/output geometries are analized.
  • Publication
    Structure of the dielectric tensor in nematic liquid crystals with topological charge
    (Optical Society of America, 2010-06) Martínez Matos, Óscar; Vaveliuk, Pablo; Moraes, Fernando Jorge Sampaio; Fumeron, Sebastien; Calvo Padilla, María Luisa
    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.