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© 2009 IOP Publishing Ltd. The financial support of the Spanish Ministry of Science and Innovation under Grant TEC2008-04125 and CAM-CG-300 is acknowledged. One of us (JPR) acknowledges the Consejo Superior de Investigaciones Científicas (CSIC) for the grant accorded (JAE-pre Fellowship). We are indebted to V. Lakshminarayanan for helpful suggestions and discussions., We present a formalism based upon dynamic programming (DP), to characterize light propagation in particular GRIN (gradient index) media by analyzing ray trajectories associated with skew-type rays. We study the conditions for the formation of periodic trajectories and stability of the system. We perform a comparative study with the classical formalism based on the Hamilton-Jacobi equation. The DP formalism allows representation in phase (momentum) space., Ministerio de Ciencia e Innovación (MICINN), España, Consejo Superior de Investigaciones Científicas (CSIC), España, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2009 Optical Society of America. The financial support of the Spanish Ministry of Science and Innovation under projects TEC2005-02180, TEC2008-04105 and Santander-Complutense project PR-34/07-15914 are acknowledged. The authors thank Dr. Óscar Martínez-Matos for valuable discussions., A flexible optical system able to perform the fractional Fourier transform (FRFT) almost in real time is presented. In contrast to other FRFT setups the resulting transformation has no additional scaling and phase factors depending on the fractional orders. The feasibility of the proposed setup is demonstrated experimentally for a wide range of fractional orders. The fast modification of the fractional orders, offered by this optical system, allows to implement various proposed algorithms for beam characterization, phase retrieval, information processing, etc., Ministerio de Ciencia e Innovación (España), Banco Santander Central Hispano (BSCH), Universidad Complutense de Madrid (UCM), Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2011 Optical Society of America. The financial support of the Spanish Ministry of Science and Innovation under project TEC2008-04105 is acknowledged. José A. Rodrigo gratefully thanks a “Juan de la Cierva” grant and A. Cámara acknowledges the financial support of the “Comunidad de Madrid” and the European Social Fund., In this work, we propose a robust and versatile approach for the characterization of the complex field amplitude of holographically generated coherent-scalar paraxial beams. For this purpose we apply an iterative algorithm that allows recovering the phase of the generated beam from the measurement of its Wigner distribution projections. Its performance is analyzed for beams of different symmetry: Laguerre-Gaussian, Hermite-Gaussian and spiral ones, which are obtained experimentally by a computer generated hologram (CGH) implemented on a programmable spatial light modulator (SLM). Using the same method we also study the quality of their holographic recording on a highly efficient photopolymerizable glass. The proposed approach is useful for the creation of adaptive CGH that takes into account the peculiarities of the SLM, as well as for the quality control of the holographic data storage., Ministerio de Ciencia e Innovación, España, Ministerio de Economía y Competitividad, España, Comunidad de Madrid, European Social Fund, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© Optical Society of America. The financial support of the Spanish Ministry of Health, the Institute of Health “Carlos III”, and the Health Research Foundation under project 95/1518 is acknowledged. Also a grant (A. Manzanares) from the Complutense University (4829) is acknowledged., A revised formulation of the image Light distribution of an incoherent line source proposed by Steel [Rev. Opt. 31, 334-340 (1952)] is presented. Analytical and numerical results based on this new representation are given. We explicitly show that a major error in Steel's final expression generates singularities, thereby preventing convenient numerical computation., Ministerio de Sanidad y Consumo, España, Instituto de Salud Carlos III, España, Health Research Foundation, Universidad Complutense de Madrid (UCM), Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2013 Optical Society of America. Financial support from the National Research Council of Canada and Spanish Ministry of Economy (TEC2008-04105 and TEC2011-23629) is acknowledged., 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., National Research Council, Canada, Ministerio de Economía, España, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 1984 The Institute of Physics We are grateful to M. Chevalier and to Drs. V. Alcober and O. Schaerpf for useful discussions. The partial financial support given by Comisión Asesora de Investigación Científica y Técnica, Spain, is also acknowledged., The 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., Comisión Asesora de Investigación Científica y Técnica (CAICYT), España, Ministerio de Educación y Ciencia (MEC), España, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

©2011 Optical Society of America. We thank J. A. Rodrigo and R. Weigand for helpful discussions. The financial support of the Spanish Ministry of Innovation and Science, under grant TEC2008-1045 is acknowledged. One of us (M.P. Hernandez-Garay) acknowledges the MAEC-AECID (Spain) and CONACyT (Mexico) grants, P. Vaveliuk is grateful to CNPq (Brazilian federal grant agency) for financial support. We thank to Chemical Reaction Dynamics and Femtochemistry Group: J. G. Izquierdo and L. Bañares (Spanish Ministry of Science and Innovation (MICINN) through Grant CTQ2008-02578/BQU, and Consolider SAUUL CSD2007-00013). Finally, the authors gratefully the reviewers’s suggestions., The majority of the applications of ultrashort laser pulses require a control of its spectral bandwidth. In this paper we show the capability of volume phase holographic gratings recorded in photopolymerizable glasses for spectral pulse reshaping of ultrashort laser pulses originated in an Amplified Ti: Sapphire laser system and its second harmonic. Gratings with high laser induce damage threshold (LIDT) allowing wide spectral bandwidth operability satisfy these demands. We have performed LIDT testing in the photopolymerizable glass showing that the sample remains unaltered after more than 10 million pulses with 0,75 TW/cm^2 at 1 KHz repetition rate. Furthermore, it has been developed a theoretical model, as an extension of the Kogelnik's theory, providing key gratings design for bandwidth operability. The main features of the diffracted beams are in agreement with the model, showing that non-linear effects are negligible in this material up to the fluence threshold for laser induced damage. The high versatility of the grating design along with the excellent LIDT indicates that this material is a promising candidate for ultrashort laser pulses manipulations., Ministerio de Ciencia e Innovación-MICINN, España, Ministerio de Asuntos Exteriores y de Cooperación, España, Consejo Nacional de Ciencia y Tecnología CONACyT, México, CNPq (Brazilian federal grant agency), Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© Pleiades Publishing, Ltd., 2007. Partial financial support from the Spanish Ministry of Education and Science, under grant TEC2005–2180 is acknowledged., The advances in the sol-gel holographic recording materials, namely in the photopolymerizable compositions and photorefractive glasses, are reviewed. A new sol-gel holographic material is also discussed that exploits diffusion of a high-refractive-index MA:Zr complex, with the refractive index modulation of n ∼ 10^2 and negligible scattering., Ministerio de Educación y Ciencia, España, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 1996 Optical Society of America. The support of this study by the National Aerospace Institute Ministry of Defense) and the partial financial support from the Comisión Interministerial de Ciencia y Tecnología (Ministry of Education and Science) are acknowledged., The theoretical model for an off-Bragg on-axis conversion between a Gaussian beam with cylindrical phase function and a plane wave by a volume aperiodic nonplanar inhomogeneous holographic grating is presented. A two-wave first-order coupled-wave theoretical framework is adopted. Analytical solutions for the amplitudes of two space harmonics of the field inside the grating zone are derived. Both the chromatic and the geometric deviations from the exact Bragg condition are studied. Numerical evaluations show that some anomalous phenomena (Pendellösung fringes, angle amplification effect, achromatism) can arise. High diffraction efficiency (≈1) is predicted even for relatively large off-Bragg deviations. The deterioration of the reconstruction fidelity due to the Pendellösung effect is discussed., Instituto Nacional de Técnica Aeroespacial (INTA), España, Ministerio de Defensa, España, Comisión Interministerial de Ciencia y Tecnología, España, Ministerio de Educación y Ciencia (MEC), España, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

©2012 Optical Society of America., We experimentally demonstrate a new type of waveguide multiplexer device designed for silicon photonics, with a crosstalk level as low as -35 dB and an operational wavelength range of 300 nm. A compact device footprint of only 100 x 160 µm2 offers an excellent potential for integration with other silicon nanophotonic circuits., Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2007 American Institute of Physics. The financial support from the Spanish Ministry of Education and Science under Project No. TEC2005-02180 is gratefully acknowledged., We report results on the temporal evolution of the diffraction efficiency of volume holographic gratings recorded in a photopolymer glass incorporating Zr-based high refractive index species (HRIS) at molecular level. We record high spatial frequency gratings in this material with diffraction efficiencies near 100%. A two-component diffusion model is introduced for the evolution of refractive index modulation in darkness. Diffusion parameters for the Zr-based HRIS and monomer components have been determined. Codirectional diffusion of both components is demonstrated. The results show the feasibility for tailoring in this photomaterial holographic gratings with high diffraction efficiency over a wide range of spatial frequencies. (C) 2007 American Institute of Physics., Ministerio de Educación y Ciencia, España, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2011 Optical Society of America. The project TEC2008-04105 from the Spanish Ministry of Science and Innovation is acknowledged. A. Cámara and J. A. Rodrigo thank the financial support from the Consejería de Educación de la Comunidad de Madrid together with the European Social Fund and Juan de la Cierva grant., We show the adaptation of a multifunctional optical system consisting of two spatial light modulators for the optimal measurement of the Radon-Wigner transform of one-dimensional signals. The proposed Radon-Wigner display allows reconstructing the Wigner distribution and the phase or the mutual intensity of fully or partially coherent fields, respectively. It is also suitable for the analysis of two-dimensional rotationally symmetric or separable in Cartesian coordinates optical fields. The feasibility of the proposed scheme is experimentally demonstrated in several examples., Ministerio de Ciencia e Innovación (MICINN), España, Consejería de Educación de la Comunidad de Madrid, European Social Fund, Subprograma Juan de la Cierva, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2011 American Institute of Physics. Financial support from the Spanish Ministry of Science and Innovation (MICINN) under grant TEC2008-04105 is acknowledged. A.V.V. acknowledges a fellowship from MICINN and M.P.H.G. acknowledges a fellowship from the Spanish Ministry of External Affairs and CONACyT (Mexico). We thank O. Martı´nez-Matos for helpful suggestions and discussions., 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., Ministerio de Ciencia e Innovación (MICINN), España, Ministerio de Asuntos Exteriores, España, Consejo Nacional de Ciencia y Tecnología (CONACYT), México, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2010 Optical Society of America. We thank Fransisco del Monte for valuable advice and CAI-UCM facilities. The financial support from the Spanish Ministry of Science and Innovation under projects TEC 2008-04105, CTQ2008-02578/BQU and Consolider SAUUL CSD2007-00013 is acknowledged. M. P. H.-G. and P. V. acknowledge the Spanish Ministry of Foreign Affairs and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) (Brazil) for financial support, respectively., We present an approach to generate paraxial laser beams with arbitrary spatial distribution in the femtosecond time regime. The proposed technique is based upon a pair of volume phase holographic gratings working in parallel arrangement. It exploits the spatial coherence properties of the incoming laser beam in a compact and robust setup that mitigates angular and spatial chirp. The gratings were recorded in a photopolymerizable glass with a high optical damage threshold and a large optical throughput. Setup performance is studied and experimentally demonstrated by generating Laguerre-Gaussian femtosecond pulses., Ministerio de Ciencia e Innovación (MICINN), España, Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) (Brazil), Ministerio de Asuntos Exteriores y de Cooperación, España, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2004 Elsevier Ltd. World Congress on Neutron Capture Therapy (11º. 2004. Boston, EE.UU.). Both authors acknowledge the financial support of Ministerio de Ciencia y Tecnología, Spain: R.F. A.-E. through Proyecto FPA2000-0956, while M.L.C. through Proyecto TIC2002-1846. We are grateful to Dr. J.F. Crawford for interesting correspondence, Mrs. Reiko Matsuoka for providing kindly information about the activities of the NCT community and to the referees for comments and criticism. R.F. A.-E. is Associate Member of Instituto de Biocomp. y Física de Sist. Compl., Universidad de Zaragoza, Zaragoza, Spain., We summarize previous researches regarding neutron guides of small transverse cross-section (neutron fibres), smaller than those of the standard hollow guides and collimators employed currently. Those studies may not be widely known in the neutron capture therapy (NCT) community, but they may be interesting for it. Such neutron fibres could allow to deliver and concentrate neutron beams selectively in regions of size smaller than 1 mm. We present new estimates and point out and discuss some new possible specific applications of those neutron fibres, which would not replace standard NCT but could supplement it. Thus, we entertain the possibility that neutron fibres could be useful for additional therapies (in typical NCT durations) of: (i) rather small tumours, (ii) thin borders of tumours. The use of these neutron fibres could reduce the undesirable delivery of radiation to healthy tissue around regions with malignant tissue., Ministerio de Ciencia y Tecnología, España, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2003 MAIK “Nauka/Interperiodica”. This work was supported by grant no. TIC2000–2791E from the Spanish Ministry of Science and Technology., 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., Ministerio de Ciencia y Tecnología, España, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 1995 Optical Society of America., The spatial impulse response of a single variable-cross-section photoreceptor has been characterized assuming the incoming radiation to be an initial field propagating under confinement conditions inside the receptor. By application of Fourier analysis the total transfer function is determined. Both the outer and the inner segments are characterized as low-pass filters. The dependence of the transfer function on the modal parameter is analyzed., Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2004 Optical Society of America. This research was partially supported by project TIC2002-1846, Ministerio de Ciencia y Tecnologia, Spain., We report the first experimental results, to our knowledge, with fractal zone plates implemented in a liquid-crystal 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., Ministerio de Ciencia y Tecnología, España, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

@ 1989 IOP Publishing Ltd. MLC wants to thank the US-Spanish Joint Committee for Scientific and Technological Cooperation for financial support. This work was supported in part by a National Eye Institute granEtY 03674 from the National Institutes of Health, Bethesda, MD. We also acknowledge the interest and support of J M Enoch. Thanks also to Christina Vigil for working on the manuscript., The authors present a mathematically exact formulation of the initial field striking the aperture of an absorbing optical waveguide, via an integral equation description. An analysis of the residual scattering by the waveguide is presented. Because of the presence of the non-negligible absorption coefficient, the solution for the fraction of the confined power is obtained by performing non-trivial integrations of Bessel and Hankel functions with complex arguments. In order to carry out a numerical analysis a specific computational method is applied by using an approximated polynomial expansion whose validity is also discussed., The Joint Committee for Scientific and Technological Cooperation, EE.UU.-España, National Eye Institute (NEI), EE.UU., National Institutes of Health (NIH), EE.UU., Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 1989 Optical Society of America. International Symposium on the Technologies for Optoelectronics (1987. Cannes, Francia). Conference Laser Technologies in Industry (1988. Oporto, Portugal). HOSPIA Meeting (1988. Madrás, India). Part of this work was financially supported by the CAICYT (Spanish Advisory Commission for Scientific and Technological Developments). Partial results were presented at the International Symposium on the Technologies for Optoelectronics, 16-19 Nov. 1987, Cannes, France, at the Conference Laser Technologies in Industry, 6-8 June 1988, Porto, Portugal, and at the HOSPIA Meeting, 12-18 Dec. 1988, Madras, India. We are indebted to 0. D. D. Soares from Porto University for helpful suggestions and discussions and to P. K. Mondal for his advice., A mathematical model for describing a holographic coupler–optical fiber system is considered. The object wave to be recorded in the hologram is assumed to be a polarized wave which is scattered by the optical fiber. In the reconstruction the optimal condition for the diffracted wavefront to be coupled to a second fiber is obtained and numerically analyzed., Comisión Asesora de Investigación Científica y Técnica (CAICYT), España, Ministerio de la Presidencia, España, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2013 American Institute of Physics. We are indebted to F. Del Monte (Institute for Materials Science, Spanish Research Council) for helpful discussions. Financial support from the Spanish Ministry of Science and Innovation (MICINN) under Grant Nos. TEC2008-04105 and TEC2011-23629 is acknowledged., A novel formulation and synthesis method to overcome the thickness limitations in samples of photopolymerizable glasses with high refractive index species is presented. The reported method allows the recording of volume holographic diffraction gratings in samples of similar to 500 mu m thickness with a high optical quality and low scattering. Holographic grating recording is performed in a single coherent light exposure step, resulting in volume gratings of high optical quality. A holographic notch filter implemented in a 500 mu m thick photopolymerizable glass with a spectral bandwidth below 0.3 nm and an excellent filter extinction ratio of <-27 dB is also demonstrated., Ministerio de Ciencia e Innovación (MICINN), España, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 1997 Optical Society of America. The Optical Society (OSA) Annual Meeting (1995. Portland, Oregón, EE.UU.). Congress of the International Comission for Optics (ICO) (17º. 1996. Taejon, Corea del Sur). This work was supported in part by the School of Optometry of the University of Missouri–St. Louis (UMSL). A UMSL research grant is also gratefully acknowledged. We also thank Jerry Christensen, Dean, School of Optometry, USML, for support during the initial stages of this research program. Additional financial assistance from the Spanish Ministry of Education and Science (DGICYT) under project PR94-362 to M. L. Calvo is also acknowledged. Partial results were presented at the OSA Annual Meeting (Portland, Oregon, October 1995) and at the ICO-XVII Congress (Taejon, Korea, August 1996). The authors also thank an anonymous referee for a careful review and R. F. Álvarez-Estrada and G. F. Calvo for helpful suggestions and discussions., We apply techniques of optimal-control theory, namely, the methods of dynamic programming, to the problem of light propagation in optical waveguides. This formulation is equivalent to the resolution of an eikonal equation. We illustrate this optimization technique for the case of an ideal parabolic refractive-index-profile distribution. We discuss the possibility of extending this procedure to other types of optical waveguides and optical media., School of Optometry of the University of Missouri–St. Louis (UMSL), EE. UU., Subdirección General de Proyectos (DGICYT), España, Ministerio de Educación y Ciencia (MEC), España, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 1978 The Institute of Physics This work is based upon a PhD Thesis presented by M. L. Calvo at the University of Madrid. We thank Professor A. Durán for his direction and encouragement and Professor J. Solana for a critical reading of the manuscript., The interaction and diffraction of a classical electromagnetic wave by a thin slab characterised by a periodic dielectric permeability is studied rigorously, thereby completing previously existing studies. New integral equations for the induction vector in terms of a suitable Green function, are presented, and a condition which ensures the convergence of their iterations is obtained. A bound for the error of the usual Debye-Born-Rayleigh-Gans approximation to the diffraction amplitudes is given., Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2005 Taylor & Francis. Research supported by projects TIC2002-1846 and TIC2002-11581-E Ministerio de Educación y Ciencia, Spain. T. Alieva acknowledges receipt of a ‘‘Ramón y Cajal’’ grant from Ministerio de Educación y Ciencia, Spain. The authors acknowledge the technical support of Hamamatsu (R. Díaz) in providing the CCD camera for these experiments., The paper reports studies, both experimental and using numerical simulation, of the Fresnel diffraction by recently introduced fractal zone plates associated with triadic and quintic Cantor sets. The evolution of the intensity patterns at planes transversal to the propagation direction is presented. A series of conventional and doughnut-like foci are observed around the principal focus. The position, depth and size of the foci depend on similarity dimensions and the fractal level of the encoded fractal structures, both directly related to the number of the corresponding Fresnel zones., Ministerio de Educación y Ciencia (MEC), España, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 1986 The Institute of Physics We are grateful to Dr. J. W. Fowler, from Gray Laboratory, Mount Vernon Hospital, for an interesting correspondance containing useful comments., For pt.I see ibid., vol.17, p.475 (1984). The possible confined propagation of slow (thermal) neutrons along cladded waveguides of small cross section (fibres) is studied, in order to improve a previously published analysis. Quite suitable possibilities for the core of the waveguide could be either Al or Si (or vacuum), so as to allow for confined propagation of neutrons along reasonable lengths, without large scattering and absorption losses. Tentative possibilities for the cladding could be either Ni or Fe. The bending losses are analysed for a curved neutron fibre in two spatial dimensions. Such bending losses turn out to be completely negligible, except in the case of a small radius of curvature Rc. To quote some typical values, for any fibre diameter between 0.1 and 1 mu m and reasonable lengths for it (between 5 and 10 cm), bending losses can be neglected other than for Rc

© 2003 MAIK “Nauka/Interperiodica”. Grant no.TIC 2000-2791E from the Spanish Ministry of Science and Technology is acknowledged. T.A. would like to thank the Spanish Ministry of Education, Culture, and Sport for financial support (grant no.SB2000-0166)., Experimental results are presented for light diffraction under the Fresnel regime by two types of fractal gratings: triadic Cantor bars and Vicsek fractals. It is shown that the evolution of the diffraction patterns in the Fresnel regions reveals the hierarchical structure of deterministic fractal gratings., Ministerio de Ciencia y Tecnología, España, Ministerio de Educación, Cultura y Deporte (MECD), España, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2005 Tatiana Alieva et al. This work has been financially supported partially by the project TIC 2002-01846 from the Spanish Ministry of Education and Science and by the project IST-2001-34168 “Two dimensional optical storage for high density and high data rate” from the European Commission. T. Alieva thanks the Spanish Ministry of Science and Technology (“Ramon y Cajal”grant)., We review the progress achieved in optical information processing during the last decade by applying fractional linear integral transforms. The fractional Fourier transform and its applications for phase retrieval, beam characterization, space-variant pattern recognition, adaptive filter design, encryption, watermarking, and so forth is discussed in detail. A general algorithm for the fractionalization of linear cyclic integral transforms is introduced and it is shown that they can be fractionalized in an infinite number of ways. Basic properties of fractional cyclic transforms are considered. The implementation of some fractional transforms in optics, such as fractional Hankel, sine, cosine, Hartley, and Hilbert transforms, is discussed. New horizons of the application of fractional transforms for optical information processing are underlined., Ministerio de Educación y Ciencia (MEC), España, Comisión Europea, Ministerio de Ciencia y Tecnología, España, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2003 IOP Publishing Ltd Congress of the International Commission for Optics (19º. 2002. Florencia, Italia). This work was supported partially by the Spanish Ministry of Science and Technology under the project TIC2002-01846. Part of the results of this work were presented at the 19th Congress of the International Commission for Optics, Firenze, Italy, 25–31 August 2002 [13]., We consider Fresnel and Fraunhofer diffraction on regular structures generated by multiplicative iterative procedures. We prove that the iterative procedure of field construction is preserved during Fresnel diffraction, while the initiator of the structure in the Fresnel region is the Fresnel transform of the original structure. The diffractive field in the Fraunhofer region is quasi-periodic. The theoretical results are proved experimentally., Ministerio de Ciencia y Tecnología, España, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© Pleiades Publishing, Ltd., 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., Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© The Authors. All rights reserved. The financial support of the Spanish Ministry of Science and Innovation (MICINN), grant TEC2008-04105 is acknowledged. We are indebted to Maria Paz Hern´andez-Garay, Ana Manzanares and Oscar Martínez-Matos for their very valuable support and suggestions., We present a revisited study of the Thompson-Wolf experiment earlier developed in 1957 with the aim to characterize the degree of spatial coherent of a luminous source. We develop further experiments by using laser sources under various modal regimes. We analyze the experimental results., Ministerio de Ciencia e Innovación (MICINN), España, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2012 Optical Society of America. Financial support from the Spanish Ministry of Science and Innovation (MICINN) is acknowledged under grants TEC2008-04105 and TEC2009-10152., 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 mu m. 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., Ministerio de Ciencia e Innovación (MICINN), España, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 1987 Optical Society of America. This work was supported in part by grant EY03674 from the National Eye Institute, National Institutes of Health, Bethesda, Md. M. L. Calvo was supported by a grant from the U.S.- Spain Joint Committee for Scientific and Technological Cooperation Program. We thank J. M. Enoch for support and encouragement., An exact formulation of the electromagnetic field striking an optical waveguide is presented and compared with the decomposition relationship used in the literature. The expression for the critical angle is derived as a natural consequence of this formulation. Equations for the total fraction of power confined within a waveguide are derived and analyzed for the special case of absorbing waveguides. An explicit expression is derived for the fraction of energy confined within a waveguide supporting two sets of modes., National Eye Institute (NEI), EE.UU., National Institutes of Health (NIH), EE.UU., U.S.-Spain Joint Committee for Scientific and Technological Cooperation Program, (España - EE.UU.), Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2001 American Institute of Physics. One of the authors (P.C.) would like to thank D. J. Carlsson, J. D. Worsfold, and F. del Monte for stimulating discussions. They also thank the Rectorate of the Complutense University for facilitating this work., 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 x 10(-3), making this photopolymerizable material suitable for use in holographic data storage., Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2000 Optical Society of America. International Conference on Optical Science and Applications for Sustainable Development (2000. Dakar, Senegal). This research was financially supported by the Rectorate of the Complutense University of Madrid (UCM), under Multidisciplinary Project PR486/97-7477/97. T. Alieva is grateful for a grant from UCM. Partial results of this study were presented at the International Conference on Optical Science and Applications for Sustainable Development, Dakar (Senegal), April 10–14, 2000., In this study the general algorithm for the fractionalization of the linear cyclic integral transforms is established. It is shown that there are an infinite number of continuous fractional transforms related to a given cyclic integral transform. The main properties of the fractional transforms used in optics are considered. As an example, two different types of fractional Hartley transform are introduced, and the experimental setups for their optical implementation are proposed., Universidad Complutense de Madrid (UCM), Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2014 AIP Publishing LLC. We thank J. A. Rodrigo and T. Alieva for valuable discussions and advice. We thank the financial support from the Spanish Ministerio de Economía y Competividad under Projects TEC 2011-23629, CTQ2008-02578/BQU, and CTQ2012-37404-C02-01 and Consolider program SAUUL CSD2007-00013 and from Conselho Nacional de Desenvolvimento. The facilities provided by the Center of Ultrashort Lasers at Madrid Complutense University are gratefully acknowledged., A procedure to characterize the induced damage and the incubation effects in volume transmission gratings under femtosecond laser pulse train illumination is presented. It was also developed a formalism that explains the damage processes. Our proposal was employed on glass gratings to show the effectiveness of the method and its potential to design transmission gratings with enhanced laser induced damage threshold. This procedure is able to be extended to any transmission grating composed by chemically non-uniform material, opening up new perspectives to femtosecond laser pulse shaping., Spanish Ministerio de Economía y Competividad, Consolider program SAUUL, Conselho Nacional de Desenvolvimento, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2003 Optical Society of America. Congress of the International Commission for Optics (19º. 2002. Florencia, Italia). The authors gratefully acknowledge financial support from the New Del Amo Foundation under the New Del Amo Joint Academic Project (University of California–Universidad de Madrid) and from the Universidad Complutense de Madrid under Multidisciplinary Project PR486/97-7477/97. Partial results were presented at the 19th Congress, ‘‘Optics for the quality of life,’’ International Commission for Optics, Florence, Italy, August 25–30, 2002., We develop a computational method for calculating the spatial profile of the electromagnetic field after scattering by an array of waveguides. Our formalism is very general and includes chromatic dependence, the influence of the array arrangement, and other effects such as the effect of stress. Our calculations of the amplitude and phase of scattered light provide valuable information about the features of the waveguides. These results can be applied to different areas of study, such as biological waveguides and fiber sensing., New Del Amo Foundation, Universidad Complutense de Madrid (UCM), University of California, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2006 IEEE. Iberoamerican Meeting on Optics (RIAO)/ Latin American Meeting on Optics, Lasers, and Their Applications (OPTILAS) (5ª / 8ª. 2004. Porlamar, Venezuela). This work was supported by the Spanish Ministry of Science and Technology under project TIC2002-1846 and the National Research Council of Canada. Preliminary partial results were presented at the V Ibero-American Optics Meeting (RIAO) and VIII OPTILAS, October 2–8, 2004, Porlamar, Venezuela., The authors propose a new wavelength-dispersive principle based on waveguide group-index modification and apply this principle in a new type of arrayed waveguide dispersive element based on modified group index. The element is composed by an array of waveguides consisting of two sections with different group indexes. We deduce the applicable dispersion formula and demonstrate that the group-index modification can be used for controlling or enhancing device wavelength dispersion. Two device examples are provided. First, dispersive properties of a waveguide array with silicon on insulator (SOI) straight waveguides with group index modified by waveguide widening are calculated. Then, the authors show that by placing the element with modified group index in a phased array of a conventional arrayed waveguide grating (AWG) device, the dispersive properties of the AWG are markedly enhanced. Dispersion-enhancement factor of up to 60 is calculated for a compact demultiplexer designed for SOI platform with group index modified by photonic-bandgap effect., Ministerio de Ciencia y Tecnología, España, National Research Council of Canada, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2013 Optical Society of America. Financial support from the Spanish Ministry of Economy is acknowledged under grants TEC2008-04105 and TEC2011-23629., We report a stationary Fourier-transform spectrometer chip implemented in silicon microphotonic waveguides. The device comprises an array of 32 Mach-Zehnder interferometers (MZIs) with linearly increasing optical path delays between the MZI arms across the array. The optical delays are achieved by using Si-wire waveguides arranged in tightly coiled spirals with a compact device footprint of 12 mm(2). Spectral retrieval is demonstrated in a single measurement of the stationary spatial interferogram formed at the output waveguides of the array, with a wavelength resolution of 40 pm within a free spectral range of 0.75 nm. The phase and amplitude errors arising from fabrication imperfections are compensated using a transformation matrix spectral retrieval algorithm., Ministerio de Economía, España, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2000 IOP Publishing Ltd. The author is grateful to Dr. W. M. Gibson (Center for X-ray Optics, State University of New York at Albany) for an interesting correspondence and comments regarding guided neutron beams, capillary optics and neutron fibres, and to Mr. Gabriel F. Calvo for some computational help when fitting the data. The constructive criticisms of the (anonymous) referees are acknowledged. This work is dedicated to the memory of Dr. Gustavo Torres-Cisneros., The confined propagation of slow neutrons along waveguides of a small cross section (fibres), discussed theoretically some time ago and demonstrated experimentally by other authors later, is analysed further. Motivated by those experiments, a three-dimensional quantum-mechanical treatment of the associated bending losses is presented. An approximate (two-parameter) formula is derived for the transmission coefficient Upsilon of the curved fibre, which displays its explicit dependence on the curvature radius Rcu, for 0

© 1998 Elsevier Science B.V. Reunión Nacional de Óptica de la Sociedad Española de Óptica (SEDO) (1994. 4ª. Granada, España). Congress of the International Commission for Optics (ICO) (17º. 1996. Daejon,Corea del Sur). Optical Society of America (OSA)Annual Meeting (1997. Long Beach, California, EE.UU.). Partial results of this work were presented at the IVth National Meeting of the Spanish Optical Society, SEDO, Granada, Spain, September 1994; the 17th Congress of the International Commission for Optics (ICO), Taejon, Korea, August 1996; and the Annual Meeting of the Optical Society of America, Long Beach, USA, October 1997. The financial support of the Spanish Ministry of Health, the Institute of Health ‘Carlos III’ and the Health Research Foundation, under project 95/1518, and project PR160/93- 4829/93 from the Rectorate of the Complutense University are acknowledged. We are indebted to Ivan Sanz Rodriguez for his collaboration. Also, Carmen Bravo gave us computational assistance at the Computing Center of the Complutense University of Madrid. We thank Professor J.M. Enoch for helpful suggestions., 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., Health Research Foundation, Instituto de Salud Carlos III, España, Universidad Complutense de Madrid (UCM), Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2009 IOP Publishing Ltd. We thank Óscar Martínez-Matos, Francisco del Monte and José A. Rodrigo for invaluable help and many insightful discussions. The financial support of the Spanish Ministry of Education and Science (project no. TEC2005-02180) is acknowledged., 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., Ministerio de Educación y Ciencia, España, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 1987 Optical Society of America. M. L. Calvo acknowledges the partial financial support received from the Spain-USA Joint Committee for Scientific and Technical Cooperation and is grateful to Jay M. Enoch for his kind hospitality at the School of Optometry, University of California at Berkeley. R. F. Alvarez-Estrada acknowledges the partial financial support received from the Council for International Exchange of Scholars through a Fulbright-MEC Fellowship and is grateful to B. Zumino for his kind hospitality at the Theoretical Physics Group, Lawrence Berkeley Laboratory., A 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., Spain-USA Joint Committee for Scientific and Technical Cooperation (España, EE.UU.), Council for International Exchange of Scholars (CIES), EE.UU., Comisión de Intercambio Cultural, Educativo y Científico (Comisión Fulbright), España, EE.UU., Ministerio de Educación y Ciencia (MEC), España, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© Sociedad Mexicana de Física. Este trabajo está basado en la tesis doctoral presentada en la Facultad de Ciencias Físicas de la Universidad Complutense de Madrid por Pavel Chehen. Se agradece la ayuda de la Universidad Complutense de Madrid y el Instiluto Nacional de Técnica Aeroespacial (lNTA) facilitada dentro del vigente acuerdo marco entre las dos Instituciones, y también la ayuda del National Rescarch Council, Canada. durante la finalización del presente trabajo. Agradeccmos al Prof. A. Fimia por la sugerencia d de elaborar esta revisión y al árbitro por sus interesantes comentarios., 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., Universidad Complutense de Madrid (UCM), Instituto de Nacional deTécnica Aerospacial (INTA), España, National Rescarch Council of Canada, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2006 Optical Society of America., 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., Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2003 American Academy of Optometry. This work has been supported in part by the “Fundación Antonio del Amo” between the Complutense University of Madrid and the University of California. The authors thank responsible individuals in the Archivo General de Indias in Seville for making available the necessary facilities. Julian Bescós of the Ramón Areces Institution in Spain facilitated much of our work. We thank Dr. Charles Letocha, York, PA, for his kind assistance and for providing communications sent to him by Dr. Carmen Tato and Prof. Vincent Ilardi for sharing his copy of Devesa. We also thank Fathers Eliseo Abejón and Félix Rodríguez of the Colegiata de San Luis at Villagarcia de Campos in Castilla. Frank Barraclough of the Ophthalmic Antiquities International Collectors Club, UK, kindly obtained valuable references and materials for us, and we appreciate important comments by Prof. Kurt Bernardo Wolf of the Universidad Nacional Autonoma de Mexico, Cuernavaca, Mexico, and his friend/ associate Arq. Rafael Fierro Gossman of Mexico City and the valued information provided by Dr. J. William Rosenthal of New Orleans, LA., We discuss many aspects of a reproduction of a formal painting from the XVIth century. It is a portrait of Viceroy of New Spain Luis de Velasco, El Joven or Hijo (son—see text), found at the Museum of the Pecos National Monument (near Pecos and Santa Fe, New Mexico). A formal portrait of each Viceroy of New Spain was created, and this one was painted during de Velasco’s first term as Viceroy (1590 to 1595 AD). In this depiction, he is seen wearing spectacles. To our knowledge, this is the first known reference suggesting the introduction of this form of visual correction in the Spanish Colonies in the Americas and in the future United States. There are three known portraits of Luis de Velasco (son): One painting, which included his father and significant others, hangs in the Colegiata (a small cathedral) de San Luis near Valladolid, Spain. In this portrayal, he was shown as a young man without a spectacle correction. And there are two viceregal portraits (Term 1, 1590 to 1595; Term 2, 1607 to 1611) in which he wears the same spectacle correction (these are located in Mexico City)., Fundación Antonio del Amo, Universidad Complutense de Madrid (UCM), University of California, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2006 Elsevier B.V. The financial supports from the Spanish Ministry of Science and Technology under Project TIC2002-1846 and from the National Research Council of Canada are acknowledged. Partial results were presented at the V Ibero-American Optics Meeting (RIAO) and VIII OPTILAS, October 2–8, 2004, Porlamar (Venezuela)., 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., Ministerio de Ciencia y Tecnología, España, National Research Council of Canada, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2011 Optical Society of America. The financial support of the Spanish Ministry of Science and Innovation under project TEC2008-04105 and TEC2010-20307 are acknowledged. José A. Rodrigo gratefully thanks a “Juan de la Cierva” grant., We present a fast and robust non-interferomentric wavefield retrieval approach suitable for imaging of both amplitude and phase distributions of scalar coherent beams. It is based on the diversity of the intensity measurements obtained under controlled astigmatism and it can be easily implemented in standard imaging systems. Its application for imaging in microscopy is experimentally studied. Relevant examples illustrate the approach capabilities for image super-resolution, numerical refocusing, quantitative imaging and phase mapping., Ministerio de Ciencia e Innovación (MICINN), España, Subprograma Juan de la Cierva, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2010 Optical Society of America. P. V. and F. M. acknowledge financial support from CNPq (Brazilian federal grant agency). The partial financial support of the Spanish Ministry of Innovation and Science, under project TEC2008-04105is acknowledged., 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., CNPq (Brazilian federal grant agency), Ministerio de Ciencia e Innovación (MICINN), España., Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2014 SPIE, OSA, IEEE, ICO. The author would like to express sincere thanks to Aitor V. Velasco, Alejandro Cámara and Elena Alonso-Redondo for very valuable help. Moreover, to all undergraduate students of the 4th Course of the Physics Grade, Faculty of Physical Sciences, Complutense University of Madrid. Partial financial support from the Spanish Ministry of Economy under Grant TEC2011-23629 is also acknowledged., 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., Spanish Ministry of Economy, Ministerio de Ciencia y Competitividad (MINECO), España, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

© 2002 IOP Publishing Ltd. Financial assistance fromthemultidisciplinary project PR486/97-7477/97from Complutense University of Madrid and grant TIC2000-2791-E from the Spanish Ministry of Science and Technology is acknowledged. TA would like to acknowledge the financial support from Secretaría de Estado de Educación y Universidades (SB2000-0166), the Spanish Ministry of Education, Culture and Sport., The main properties of the power filtering operation in the fractional Fourier domain and its relationship to the differentiation operation are considered. The application of linear power filtering for solving the phase retrieval problem from intensity distributions only is proposed. The optical configuration for the experimental realization of the method is discussed., Universidad Complutense de Madrid (UCM), Ministerio de Ciencia y Tecnología, España, Secretaría de Estado de Educación y Universidades, Ministerio de Educación, Cultura y Deporte, España, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub