Vera Brudny

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James Elkins

School of the Art Institute of Chicago

Estela Blaisten-Barojas

George Mason University

David Seamon

Kansas State University

Armando Marques-Guedes

UNL - New University of Lisbon

Khaled Dine

University of Dr moulay taher

Tomás Machado

Unisinos

Jose Navarro Torres

Universidad Autonoma de Baja California

Surendra Singh

University of Arkansas

Franz Giessibl

University of Regensburg

Dirk K F Meijer

University of Groningen

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Papers by Vera Brudny

Exact calculations of surface impedance for periodic rough surfaces

Surface Roughness and Scattering

The concept of surface impedance has been widely used in electromagnetic theory of scattering. Fo... more The concept of surface impedance has been widely used in electromagnetic theory of scattering. For a 2D scattering problem the impedance Z(x) on a surface ∑ can be defined as (1) where E║ and H║ represent the components of the electric and magnetic fields tangential to surface ∑, x is a coordinate on the surface and n^ the unit vector normal to it. If Z(x) is known, eq. (1) can be used as a boundary condition exactly equivalent to Maxwell’s, but since it is defined in terms of the fields this knowledge requires the complete solution of the scattering problem.

$Research paper thumbnail of Diffuse light bands for p and s polarization in microrough diffraction gratings$

Diffuse light bands for p and s polarization in microrough diffraction gratings

Optik, 1994

We present here experimental evidence of the existence of a distinct band pattern in the diffuse ... more We present here experimental evidence of the existence of a distinct band pattern in the diffuse background generated by the scattering of light on a microrough diffraction grating for both polarizations of the incident light. This sort of pattern («diffuse light bands») has been previously observed and studied for p-polarized incidence, but not for s-polarized. The band structure possesses similar features for both polarizations. The pattern for p-polarized incident light can be explained in terms of surface plasmon interaction with the random roughness existing on the grating; however, the mechanisms that generate the band structure for s-polarized incidence cannot be as easily identified

Disipacion en cuerdas vibrantes y tubos de Kundt

Anales AFA, 2010

Se presenta aquí un análisis del amortiguamiento en dos casos canónicos que se suelen plantear en... more Se presenta aquí un análisis del amortiguamiento en dos casos canónicos que se suelen plantear en los primeros laboratorios: modos normales longitudinales en columnas de gas (tubos de Kundt) y modos transversales en cuerdas. En el primer caso se muestra que es posible modificar algunos parámetros relacionados con los materiales de los tubos para obtener diferentes amortiguamientos. Para esto se utilizan tubos de Kundt cubriendo sus paredes con materiales de distinto rozamiento. Se muestra que el resultado es consistente en el sentido que se obtiene un mayor amortiguamiento cuanto mayor es el rozamiento. En el caso de las cuerdas, se realiza un análisis dimensional que permite establecer la dependencia del amortiguamiento con algunos parámetros del problema. Para esto se utilizan distintas tanzas de nylon multifilamento. En todos los casos el amortiguamiento es medido a través del ancho de las campanas de resonancia. Palabras clave: sistemas resonantes -disipación -cuerdas vibrantes -tubos de Kundt. We analyze the damping effects for normal modes in Kundt tubes and in vibrating strings, two systems that are usually studied in undergraduate laboratory courses. We show that in the case of Kundt tube it is possible to modify the damping effects by changing the inner lining of the tube. For the vibrating string system we develope a dymensional analysis that allows us to establish the dependence of the damping coefficient on different variables involved in the system. We present an experimental confirmation of these predictions for multifilament nylon strings. In both cases the damping coefficient is measured through the study of resonance curves.

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$Research paper thumbnail of Anomalous Behavior Reflecting Diffraction Gratings for TE and TM Polarizations$

Anomalous Behavior Reflecting Diffraction Gratings for TE and TM Polarizations

Proceedings of SPIE - The International Society for Optical Engineering

Second harmonic generation from small particle aggregates

ABSTRACT Novel nanofabrication techniques are capable of producing nanoparticles with controled s... more ABSTRACT Novel nanofabrication techniques are capable of producing nanoparticles with controled structures which include small clusters, self-assembled particles, quantum dots, vesicles, etc. The non-linear optical scattering of these structures are important for applications, and can be used for their physical characterization. The second harmonic (SH) field radiated by a single small spherical particle has surface and bulk, dipolar and quadrupolar contributions of similar intensities and is strongly dependent of the local environment of the particle [1], in contrast to the linear case. In this work we calculate the nonlinear scattering by particle aggregates and we investigate the effects on the SH generation of the disorder induced field fluctuations and of the localization of light. We acknowledge the partial support from DGAPA-UNAM (grant IN110999), Conacyt (31120-E and 26651-E), CIP and UBACyT. [1] Vera L. Brudny, Bernardo S. Mendoza, and W. Luis Mochán, Phys. Rev. B 62, 11152 (2000).

Frustrated total internal reflection and the illusion of superluminal propagation

FTIR and the illusion of superluminality

Frontiers in Optics 2004/Laser Science XXII/Diffractive Optics and Micro-Optics/Optical Fabrication and Testing, 2004

ABSTRACT The propagation of evanescent pulses under the conditions of frustrated internal reflect... more ABSTRACT The propagation of evanescent pulses under the conditions of frustrated internal reflection (FTIR) may appear as superluminal and non-causal, but only if it is treated as a 1D tunneling phenomenon. When its 3D nature is fully accounted for, it may be simply explained through a subluminal causal theory.

Second harmonic generation from arrays of spherical particles

We calculate the optical second harmonic (SH) radiation generated by small spheres made up of a h... more We calculate the optical second harmonic (SH) radiation generated by small spheres made up of a homogeneous centrosymmetric material illuminated by inhomogeneous electromagnetic fields with arbitrary transverse and longitudinal spatial variations. We obtain expressions for the hyperpolarizabilities of the particles in terms of the multipolar bulk susceptibilities and dipolar surface susceptibilities of their constitutive material. We employ the resulting response

Update on women in physics in Argentina

AIP Conference Proceedings, 2013

Data collected 10 years ago in Argentina concluded that women in physics were underrepresented in... more Data collected 10 years ago in Argentina concluded that women in physics were underrepresented in many instances and that a "crystal ceiling" was firmly in place. We have collected updated data for several indicators and compared them with those obtained 10 years ago. Although there is not a clear conclusion to be drawn from this comparison, we try to explain the results within the framework of the changes in scientific policies in Argentina.

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Spectral impurity in gratings due to surface plasmon scattering

Optics Communications, 1991

... 5,6 OPTICS COMMUNICATIONS 1 May 1991 Spectral impurity in gratings due to surface plasmon sca... more

Second-harmonic generation from spherical particles

Physical Review B, 2000

We calculate the nonlinear dipole and quadrupole moments induced at the second-harmonic ͑SH͒ freq... more We calculate the nonlinear dipole and quadrupole moments induced at the second-harmonic ͑SH͒ frequency 2 in a small dielectric sphere by an inhomogeneous monochromatic electric field of frequency. We neglect finite-size effects and assume that the selvedge region of the sphere is thin enough so that the surface may be considered locally flat. The second-order dipole displays resonances corresponding to the excitation of dipolar and quadrupolar plasmons at and a dipolar plasmon at 2, besides the resonances in the nonlinear surface response parameters a, b, and f. The second-order quadrupole, on the other hand, has resonances corresponding to those of a, b, and f, and to the excitation of dipolar surface plasmons at only. Depending on the relation between the size of the sphere and the spatial scale of variation of the field, the SH radiation may be dominated by either dipolar or quadrupolar scattering, with a crossover region. As an application, we calculate the SH scattering of a Si sphere lying at various distances above a dielectric substrate.

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Depth resolved nonlinear optical nanoscopy

physica status solidi (b), 2003

An electromagnetic field forced to vary along a plane with a spatial scale d much smaller than it... more An electromagnetic field forced to vary along a plane with a spatial scale d much smaller than its free space wavelength λ decays exponentially along its normal with a decay length ∼d. This decay, similar to that of the wavefunction of tunneling electrons, has allowed the development of scanning near‐field optical microscopes (SNOMs), reminiscent of scanning tunneling and atomic force microscopes, which have been able to resolve structures in the nanometer scale. However, existing SNOMs are unable to determine the depth below the surface from which the optical signals arise due to the monotonic decay of the optical evanescent probe fields. In this paper we study the optical second harmonic generation (SHG) produced by mixing of the evanescent fields produced by a SNOM tip. We show that employing an appropriately spatially‐patterned tip, a non‐monotonic non‐linear probing field may be produced which has a maximum at a given distance beyond the tip, yielding a novel microscopy which m...

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Nonlinear optical nanoscope with depth resolution

SPIE Proceedings, 2004

Nonlinear optical nanoscope with depth resolution. [Proceedings of SPIE 5622, 524 (2004)]. W. Lui... more

Second-harmonic generation in arrays of spherical particles

Physical Review B, 2003

We calculate the optical second harmonic ͑SH͒ radiation generated by small spheres made up of a h... more We calculate the optical second harmonic ͑SH͒ radiation generated by small spheres made up of a homogeneous centrosymmetric material illuminated by inhomogeneous transverse and/or longitudinal electromagnetic fields. We obtain expressions for the hyperpolarizabilities of the particles in terms of the multipolar bulk susceptibilities and dipolar surface susceptibilities of their constitutive material. We employ the resulting response functions to obtain the nonlinear susceptibilities of a composite medium made up of an array of such particles and to calculate the radiation patterns and the efficiency of SH generation from the bulk and the edge of thin composite films illuminated by finite beams. Each sphere has comparable dipolar and quadrupolar contributions to the nonlinear radiation, and the composite has comparable bulk and edge contributions which interfere among themselves yielding nontrivial radiation and polarization patterns. We present numerical results for Si spheres and we compare our results with recent experiments.

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Second harmonic generation from small spherical particles

Since optical second harmonic generation (SHG) is strongly supressed within centrosymmetric syste... more Since optical second harmonic generation (SHG) is strongly supressed within centrosymmetric systems but not close to their surfaces, it has been used as the basis of a powerful spectroscopy for the study of flat surfaces. Not much attention, however, has so far been paid to SHG from non planar surfaces. In this paper we develop a theory for the SHG from small spherical particles made of homogeneous isotropic media, assuming that the selvedge is thin compared to the radius, so that it is locally charcterized by the flat surface nonlinear response. The polarization induced at opposite sides of the surface do not cancel each other when the polarizing local field is inhomogeneous. Thus, a net nonlinear dipole is induced, whose contribution to the radiated field is comparable and might even dominate over the nonlinear quadrupolar radiation. We calculate the spectrum and the radiation pattern from an overlayer of particles grown over a flat surface. We identify structures in the spectrum ...

Energy Conservation and the Manley-Rowe Relations in Surface Nonlinear-Optical Spectroscopy

Physical Review Letters, 1998

We consider the energy conservation problem for nonlinear-optical three-wave mixing processes at ... more We consider the energy conservation problem for nonlinear-optical three-wave mixing processes at the surface and in the bulk of semi-infinite centrosymmetric lossless media. Because of the intrinsic nonlocality of these processes, the corresponding Manley-Rowe relations differ from those of noncentrosymmetric media. The ensuing restrictions link the surface and bulk nonlinear susceptibility components and may be used to test theories of nonlinear response. Our analysis permits a clear separation of the intrinsic surface contribution that contains the information about the surface structure. [S0031-9007(98)06647-2]

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Comment on “Noncausal Time Response in Frustrated Total Internal Reflection?”

Physical Review Letters, 2001

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Second harmonic generation from a collection of nanoparticles

physica status solidi (b), 2003

In this paper we discuss the SH radiation produced by a composite film made up of nanosized spher... more In this paper we discuss the SH radiation produced by a composite film made up of nanosized spherical centrosymmetric homogeneous particles. Although each individual sphere is unable to radiate in the forward direction when illuminated by a plane wave, our results show that for a thin composite film illuminated by a focused gaussian linearly polarized beam the radiation pattern presents two narrow lobes displaced along the polarization direction by a small angle of the order of the diffraction‐induced angular divergence of the linear far field. The SH radiation produced by a non‐homogeneous film, on the other hand presents non‐trivial patterns which depend on the fundamental frequency, the waist of the illuminating beam, the sharpness of the edge, the density profile and both the incoming and outgoing polarizations. We hope that these results can be extended to develop characterization techniques for composite films based on surface SHG or SFG. (© 2003 WILEY‐VCH Verlag GmbH & Co. KG...

A Model for Second Harmonic Generation from Magnetized Surfaces

physica status solidi (a), 1998

ABSTRACT Based on simple magnetic dipolium model, we calculate the surface susceptibility tensor ... more ABSTRACT Based on simple magnetic dipolium model, we calculate the surface susceptibility tensor χS that characterizes the second harmonic response from centrosymmetric magnetic material. The possibility of having enhanced or reduced magnetic moments at the surface is incorporated. Certain magnetization-induced tensor components are found to be sensitive to the surface magnetization while others depend only on its bulk value.

Energy Exchange in Second-Order Nonlinear Optics in Centrosymmetric Media

physica status solidi (a), 1998

ABSTRACT Available from http://www3.interscience.wiley.com/cgi- bin/abstract/40001131/START

Exact calculations of surface impedance for periodic rough surfaces

Surface Roughness and Scattering