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Search Results: 1 - 10 of 178170 matches for " E. Garcia Caurel "
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Workshop on advanced polarimetric instrumentation: API’09
Garcia-Caurel E.
EPJ Web of Conferences , 2010, DOI: 10.1051/epjconf/20100500001
Abstract: The First NanoCharM Workshop on Advanced Polarimetric Instrumentation was focused on the instrumentation developed to work with polarised light, which is the cause of a great deal of research and study in a variety of fields, such as astronomy, telecommunications, defence, medicine, electronics, material science, metrology and many more. The workshop was therefore organised around six themes: imaging, astronomy and satellites, measurement of optical activity, Mueller matrix algebra and polarimetric data analysis, diffractometry and metrology of nanostructures, as well as new developments in polarimetric instrumentation. The workshop was founded by the European project NanoCharM the aim of which is, firstly, to coordinate research activities focusing on the characterisation of materials using polarised light (polarimetry) and, secondly, to develop communication initiatives to make scientists, decision-makers in the broadest sense of the term, industrialists and students aware of the various applications of polarised light.
Characterization of photonic structures using visible and infrared polarimetry
Ferré-Borrull J.,Garcia-Caurel E.,Olaizola S.M.,Kral Z.
EPJ Web of Conferences , 2010, DOI: 10.1051/epjconf/20100502002
Abstract: Photonic Crystals are materials with a spatial periodic variation of the refractive index on the wavelength scale. This confers these materials interesting photonic properties such as the existence of photonic bands and forbidden photon frequency ranges, the photonic band gaps. Among their applications it is worth mentioning the achievement of low-threshold lasers and high-Q resonant cavities. A particular case of the Photonic Crystals is well-known and widely studied since a long time: the periodic thin film coatings. The characterization of thin film coatings is a classical field of study with a very well established knowledge. However, characterization of 2D and 3D photonic crystals needs to be studied in detail as it poses new problems that have to be solved. In this sense, Polarimetry is a specially suited tool given their inherent anisotropy: photonic bands depend strongly on the propagation direction and on polarization. In this work we show how photonic crystal structures can be characterized using polarimetry equipment. We compare the numerical modeling of the interaction of the light polarization with the photonic crystal with the polarimetry measurements. With the S-Matrix formalism, the Mueller matrix of a Photonic Crystal for a given wavelength, angle of incidence and propagation direction can be obtained. We will show that useful information from polarimetry (and also from spectrometry) can be obtained when multivariate spectra are considered. We will also compare the simulation results with Polarimetry measurements on different kinds of samples: macroporous silicon photonic crystals in the near-IR range and Laser-Interference-Lithography nanostructured photoresist.
Absorbing photonic crystals for thin film photovoltaics
O. El Daif,E. Drouard,G. Gomard,X. Meng,A. Kaminski,A. Fave,M. Lemiti,E. Garcia Caurel,P. Roca i Cabarrocas,S. Ahn,H. Jeon,C. Seassal
Physics , 2010, DOI: 10.1117/12.854035
Abstract: The absorption of thin hydrogenated amorphous silicon layers can be efficiently enhanced through a controlled periodic patterning. Light is trapped through coupling with photonic Bloch modes of the periodic structures, which act as an absorbing planar photonic crystal. We theoretically demonstrate this absorption enhancement through one or two dimensional patterning, and show the experimental feasibility through large area holographic patterning. Numerical simulations show over 50% absorption enhancement over the part of the solar spectrum comprised between 380 and 750nm. It is experimentally confirmed by optical measurements performed on planar photonic crystals fabricated by laser holography and reactive ion etching.
A mid-infrared Mueller ellipsometer with pseudo-achromatic optical elements
E. Garcia-Caurel,A. Lizana,G. Ndong,B. Al-Bugami,C. Bernon,E. Al-Qahtani,F. Rengnez,A. De Martino
Physics , 2015, DOI: 10.1364/AO.54.002776
Abstract: The purpose of this article is to present a new broadband Mueller ellipsometer designed to work in the mid-infrared range, from 3 to 14 microns. The Mueller ellipsometer, which can be mounted in reflection or in transmission configuration, consists of a polarization state generator (PSG), a sample holder, and a polarization state analyzer (PSA). The PSG consists in one linear polarizer and a retarder sequentially rotated to generate a set of four optimal polarization states. The retarder consists in a bi-prism made of two identical Fresnel rhombs disposed symmetrically and joined by optical contact, giving the ensemble a "V" shape. Retardation is induced by the four total internal reflections that the beam undergoes when it propagates through the bi-prism. Total internal reflection allows to generate a quasi-achromatic retardation. The PSA is identical to the PSG, but with its optical elements mounted in reverse order. After a measurement run, the instrument yields a set of sixteen independent values, which is the minimum amount of data required to calculate the Mueller matrix of the sample. The design of the Mueller ellipsometer is based on the optimization of an objective criterion that allows minimizing the propagation of errors from raw data to the Mueller matrix of the sample. The pseudo-achromatic optical elements ensure a homogeneous quality of the measurements for all wavelengths. The performance of the Mueller ellipsometer in terms of precision, and accuracy, is discussed and illustrated with a few examples.
Application of Spectroscopic Ellipsometry and Mueller Ellipsometry to Optical Characterization
Enric Garcia-Caurel,Antonello De Martino,Jean-Paul Gaston,Li Yan
Physics , 2012, DOI: 10.1366/12-06883
Abstract: This article aims to provide a brief overview of both established and novel ellipsometry techniques, as well as their applications. Ellipsometry is an indirect optical technique in that information about the physical properties of a sample is obtained through modeling analysis. Standard ellipsometry is typically used to characterize optically isotropic bulk and/or layered materials. More advanced techniques like Mueller ellipsometry, also known as polarimetry in literature, are necessary for the complete and accurate characterization of anisotropic and/or depolarizing samples which occur in many instances, both in research and "real life" activities. In this article we cover three main areas of subject: basic theory of polarization, standard ellipsometry and Mueller ellipsometry. Section I is devoted to a short and pedagogical introduction of the formalisms used to describe light polarization. The following section is devoted to standard ellipsometry. The focus is on the experimental aspects, including both pros and cons of commercially available instruments. Section III is devoted to recent advances in Mueller ellipsometry. Applications examples are provided in sections II and III to illustrate how each technique works.
Effect of the anodization voltage on the porewidening rate of nanoporous anodic alumina
Mohammad Mahbubur Rahman,Enric Garcia-Caurel,Abel Santos,Lluis F. Marsal,Josep Pallares,Josep Ferre-Borrull
Physics , 2012, DOI: 10.1186/1556-276X-7-474
Abstract: A detailed study of the pore-widening rate of nanoporous anodic alumina layers as a function of the anodization voltage was carried out. The study focuses on samples produced under the same electrolyte and concentration but different anodization voltages within the self-ordering regime. By means of ellipsometry-based optical characterization, it is shown that in the porewidening process, the porosity increases at a faster rate for lower anodization voltages. This opens the possibility of obtaining three-dimensional nanostructured nanoporous anodic alumina with controlled thickness and refractive index of each layer, and with a refractive index difference of up to 0.24 between layers, for samples produced with oxalic acid electrolytes.
Asymptotic H?lder absolute values
E. Mu oz Garcia
International Journal of Mathematics and Mathematical Sciences , 2002, DOI: 10.1155/s0161171202110398
Abstract: We prove that asymptotic Hölder absolute values are Hölder equivalent to classical absolute values. As a corollary we obtain a generalization of Ostrowski's theorem and a classical theorem by E. Artin. The theorem presented implies a new, more flexible, definition of classical absolute value.
Educa??o brasileira: da realidade à fantasia
Garcia, Walter E;
Cadernos de Pesquisa , 1999, DOI: 10.1590/S0100-15741999000200010
Abstract: the text presented here: at the request of the educational policy group of the anped, perhaps adds nothing new to what everyone already knows about the state of education in our country. with the exception of some nuances that have arisen in the political management of educational issues during recent years, the better part of the analysis restates concepts and information already existing in the public domain. however, the emergence of marketing as a fundamental means of producing facts and creating a metareality very different from what is really happening in the country's daytoday school life has inevitable repercussions on the course of events.
Stochastic modelling of intermittent scrape-off layer plasma fluctuations
O. E. Garcia
Physics , 2012, DOI: 10.1103/PhysRevLett.108.265001
Abstract: Single-point measurements of fluctuations in the scrape-off layer of magnetized plasmas are generally found to be dominated by large-amplitude bursts which are associated with radial motion of blob-like structures. A stochastic model for these fluctuations is presented, with the plasma density given by a random sequence of bursts with a fixed wave form. Under very general conditions, this model predicts a parabolic relation between the skewness and kurtosis moments of the plasma fluctuations. In the case of exponentially distributed burst amplitudes and waiting times, the probability density function for the fluctuation amplitudes is shown to be a Gamma distribution with the scale parameter given by the average burst amplitude and the shape parameter given by the ratio of the burst duration and waiting times.
Rigidity of AMN vector spaces
E. Munoz-Garcia
Mathematics , 2000,
Abstract: A metric vector space is asymptotically metrically normable (AMN) if there exists a norm asymptotically isometric to the distance. We prove that AMN vector spaces are rigid in the class of metric vector spaces under asymptotically isometric perturbations. This result follows from a general metric normability criterium. If the distance is translation invariant and satisfies an approximate multiplicative condition then there exists a lipschitz equivalent norm. Furthermore, we give necessary and sufficient conditions for the distance to be asymptotically isometric to the norm.
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