Person: Calvo Padilla, María Luisa
Universidad Complutense de Madrid
Faculty / Institute
Now showing 1 - 10 of 135
PublicationMultiple scattering of classical electromagnetic waves by volume gratings: completion of Fujiwara's solution(Taylor and Francis Ltd., 1999-02-15) Calvo Padilla, María Luisa; Cheben, PavelWe present a general formulation for multiple scattering of classical electromagnetic waves by volume gratings. Fujiwara's electron multiple scattering theory is modified and extended to the case of both, the transmission and the reflection geometries. The analytical solution for the amplitude Φ_n corresponding to the nth scattering order is given. The convergence of the solution is proved for the transmission by a sinusoidal symmetric phase grating. By employing a structural Green's function and a vectorial formulation for diffraction of a classical electromagnetic wave by a thin periodical slab, as previously given by Alvarez-Estrada and Calvo, the solution for the back scattered field amplitude is derived and shown to coincide with that obtained within the framework of the multiple scattering theory. PublicationIntroduction to gyrator transform(American Institute of Physics (AIP), 2007) Alieva, Tatiana Krasheninnikova; Rodrigo Martín-Romo, José Augusto; Calvo Padilla, María LuisaWe 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. PublicationDiffraction on the structures generated by the multiplicative iterative procedures(SPIE--The International Society for Optical Engineering, 2003) Alieva, Tatiana Krasheninnikova; Calvo Padilla, María LuisaThe Fresnel and Fraunhofer diffraction on the regular structures generated by the multiplicative iterative procedures is considered. It is proved that the iterative procedure of field construction is preserved during Fresnel diffraction, meanwhile the initiator of the structure in the Fresnel region is the Fresnel transform of the original one. The theoretical results are proved experimentally. PublicationEdge 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, VasudevanWe 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. PublicationPhotopolymerizable sol-gel nanocomposites for holographic recording(IOP Publishing Ltd., 2009-02) Calvo Padilla, María Luisa; Cheben, PavelThe 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. PublicationEdge And Line Detection - Interpretation Using The Conrady Criterium(The International Society of Optical Engineering (SPIE), 1993) Calvo Padilla, María Luisa; Chevalier del Río, Margarita; Lakshminarayanan, Vasudevan PublicationWave-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 LuisaWe 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. Publicationm-Learning and holography: compatible techniques?(Society of Photo-optical Instrumentation Engineers, 2014) Calvo Padilla, María LuisaSince 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. PublicationFresnel 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, AndréWe 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. PublicationStress sensor based on light scattering by an array of birefringent optical waveguides(SPIE--The International Society for Optical Engineering, 2003) Limeres, J.; Calvo Padilla, María Luisa; Lakshminarayanan, Vasudevan; Enoch, Jay M.We propose a new stress-sensing technique based upon measurement of light scattering produced by an array of birefringent waveguides. When external; stress is applied to the array of waveguides, their optical properties are modified via the photo-elastic effect. By monitorizing the scattered light amplitude this change can be detected and analysed in order to assess the strength and direction of the external force.