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
28 results
Search Results
Now showing 1 - 10 of 28
Item Nonlinear Effects in the Holographic Register: an Improved Alternative to Kozma Model(Optik, 1986) Pedraza Velasco, María Lourdes de; Calvo Padilla, María LuisaItem Coupled wave analysis for a reflection dephased mixed hologram grating(Optical and Quantum Electronics, 1986) Guibelalde del Castillo, Eduardo; Calvo Padilla, María LuisaA coupled-wave analysis is given for a mixed hologram grating. The effect of spatial dephasing between the absorption and phase grating which was previously presented in transmission gratings is now developed for reflection ones. The effect is presented analytically and evaluated numerically for several cases. The analysis is motivated by the photorefractive effect in electro-optic crystals.Item Optical image processing to determine the optical properties of cellular membranes(Applied Optics, 1984) Carreras Béjar, Carmen; Chevalier del Río, Margarita; Calvo Padilla, María LuisaIn 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.Item Corrections to Raman-Nath Diffraction by Volume Holograms(Optica Acta: International Journal of Optics, 1982) Juncos del Egido, Purificación; Calvo Padilla, María LuisaIn this work we present a general formulation of the corrections to the Raman-Nath approximation for the diffracted field by a volume hologram, based on integral equations. An approximate analytic expression is given for the first correction. Numerical evaluations of this correction are also presented.Item Electromagnetic scattering by an infinite inhomogeneous dielectric cylinder: New Green’s function and integral equations(Journal of Mathematical Physics, 1980) Fernández Álvarez-Estrada, Ramón; Calvo Padilla, María LuisaThe scattering of electromagnetic waves by an infinite dielectric cylinder with variable dielectric permeability presents, in general, certain mathematical difficulties regarding the construction of rigorous solutions. We give a new divergenceless tensorGreen’s function, specially appropriate for cylindrical symmetry, and, in terms of it, present new scattering integral equations. We prove that the series for med by all successive iterations of those scattering integral equations converge under certain conditions. Suitable transformations lead to new integral equations with Hilbert–Schmidt kernels, which imply further rigorous results.Item Initial field and energy flux in absorbing optical waveguides. II. Implications(Journal of the Optical Society of America A-Optics Image Science And Vision, 1987) Lakshminarayanan, Vasudevan; Calvo Padilla, María LuisaWe present here numerical estimates of the density and flux of energy based on physical parameters associated with the absorption properties of certain types of absorbing optical waveguides. These results are based on a theoretical formalism established previously for the initial field incident upon the entrance pupil of an absorbing optical waveguide. Based on these results, the mechanisms of confined energy transmission and possible cross talk between neighboring waveguides are discussed. Some comments on the behavior of Bessel functions with complex arguments are also included in the discussion.Item Three-dimensional analysis of bending losses in dielectric optical waveguides with arbitrary refractive-index profile(Journal of the Optical Society of America A-Optics Image Science And Vision, 1987) Fernández Álvarez-Estrada, Ramón; Calvo Padilla, María LuisaA three-dimensional analysis of bending losses in dielectric optical waveguides is presented. It constitutes a nontrivial generalization of previous two- and three-dimensional studies by other authors. Our analysis is based on homogeneous integral equations for the total radiation field and suitable asymptotic approximations for Green’s functions. A key role is played by a new three-dimensional approximation for a relevant Bessel function with large order and argument (the former being larger than the latter). A nontrivial check of the consistency of all those approximations is given. General formulas are presented for the radiated field and the energy flow and for a bending-loss coefficient in three dimensions. Numerical results are also given, in order to assess the difference between the results of other authors and ours. Such a difference is rather small for monomode behavior near cutoff, increases as the behavior of the waveguide changes from monomode to multimode, and decreases as the parameter V increases for a given core radius and propagation mode.Item Applications of hybrid image-processing for the determination of the optical-properties of cellular membranes(Proceedings of the Society of Photo-Optical Instrumentation Engineers, 1983) Chevalier del Río, Margarita; Calvo Padilla, María LuisaItem Neutron fibres: a possible application of neutron optics(Journal of Physics D: Applied Physics, 1984) Fernández Álvarez-Estrada, Ramón; Calvo Padilla, María LuisaThe authors study confined propagation of slow (thermal) neutrons along (non-hollow) solid fibres made of certain elements (Ti, Mn, ...) such that amplitude for the low-energy nuclear scattering of neutrons on them be negative. Geometrical optics and quasiclassical descriptions, procedures for confining the neutrons, and some applications to radiotherapy are outlined. The confined propagation modes for slow neutrons along infinite homogeneous circular fibres without and with nuclear absorption are analysed. Some estimates of the spectral density in the neutron flux and its attenuation are outlined. In order to assess lattice periodicity effects, the potential seen by a neutron inside an infinite periodic solid fibre and its confined propagation are discussed in detail. Here the authors find wide allowed and small forbidden bands for the neutron energy along the periodic fibre: well inside the allowed bands the neutron propagation modes reduce, as a first approximation, to those for the homogeneous fibre. Lattice vibration effects and the penetration, confinement and eventual scattering of neutrons by a homogeneous fibre are also analysed.Item Holographic Coupler / Grin Medium : Characterization Of The Coupling Optimization(Holographic Optics II: Principles and Applications, 1989) Pedraza Velasco, María Lourdes de; Calvo Padilla, María LuisaThe interconnection problems in the use of optical fibers for signal transmission is a very active area of research involving several fields such as optical communication techniques and holography. Various authors have studied the efficiency of the transfer of energy from the first fiber to the second one by using a holocoupler as connecting medium. In an earlier workwe developed a mathematical model based upon the scattering by a dielectric optical waveguide, the scattered field acting as the object wave in the recording process of the holocoupler. In the present work we propose a new system where a GRIN medium is acting as the signal transmitter. We have studied the optimal conditions for the holocoupler/Grin medium system. For that we have considered two different taper shapes generating the GRIN medium and, we have made comparative studies for the results obtained in both cases. Some conclussions are withdrawn in relation to the parameters of the GRIN medium for the coupling optimization.
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