Search results for "Polarization"

2021

Abstract Reliable patient-specific ventricular repolarization times (RTs) can identify regions of functional block or afterdepolarizations, indicating arrhythmogenic cardiac tissue and the risk of sudden cardiac death. Unipolar electrograms (UEs) record electric potentials, and the Wyatt method has been shown to be accurate for estimating RT from a UE. High-pass filtering is an important step in processing UEs, however, it is known to distort the T-wave phase of the UE, which may compromise the accuracy of the Wyatt method. The aim of this study was to examine the effects of high-pass filtering, and improve RT estimates derived from filtered UEs. We first generated a comprehensive set of UE…

Dielectric and dynamic-mechanical behaviour of ethylene-vinyl alcohol copolymers

1983

Abstract Dynamic-mechanical and dielectric measurements on ethylene-vinyl alcohol copolymers with two different vinyl alcohol contents and, for comparison on polyvinylalcohol and low density polyethylene, have been carried out in order to clarify the nature of the relaxation peak. The relaxation peak observable in the dielectric loss curves of the copolymers has been assigned to the interfacial polarization, MWS type, occurring between hydrogen bonded hydroxyl groups and the apolar polyethylene segments. The shoulder also present in the e″-T curves of the copolymers seems to correspond to the glass transition peak which is hidden since the dielectric loss curve increases quickly because of …

Electromechanical coupling in anodic niobium oxide: Electric field-induced strain, internal stress, and dielectric response

2012

Seemingly, contradictory results have been reported so far for electrostriction in anodic oxides. Furthermore, no definitive agreement could be obtained with theory. In this paper, in situ techniques are combined to elucidate electrostriction in anodic niobium oxide. The dependence of strain, internal stress, and dielectric constant on the electric field is measured by, respectively, spectroscopic ellipsometry, curvature, and impedance measurements. The through-thickness strain is tensile and proportional to the square of the electric field. The in-plane internal stress is compressive and proportional to the square of the electric field at low field values. The internal stress is predicted …

Controlling ground-state rotational dynamics of molecules by shaped femtosecond laser pulses

2004

We report controlled excitation of ground-state rotational wave packet by pulse-shaping technique. The experiment is conducted in nitrogen $({\mathrm{N}}_{2})$ at room temperature and atmospheric pressure. A femtosecond laser pulse produces rotational coherences in the vibronic ground state of ${\mathrm{N}}_{2}$ through an impulsive Raman process. The laser pulse is tailored using a spatial light modulator producing spectral phase modulation. Periodic phase steps are applied in order to control the excitation of specific rotational Raman transitions. The outcome is the modification of the relative excitation between odd and even rotational states which allows the control of the symmetry and…

Integrated plasmonic waveguides: A mode solver based on density of states formulation

2009

International audience; We express the density of states (DOS) near guided resonances of plasmonic waveguides by using multiple-scattering theory. In direct analogy with the case of localized electronic defect states in condensed matter, we demonstrate that optical DOS variations follow a lorentzian profile near guided modes resonances. The lorentzian shape gives quantitative information on the guided modes (effective index, propagation length, and polarization state). We numerically investigate both leaky and bound (lossy) modes supported by dielectric-loaded surface-plasmon-polariton waveguides.

Characterizing weld pool surfaces from polarization state of thermal emissions

2013

International audience; In this Letter, a vision-based remote sensing methodology is proposed to measure the topography of weld pool surfaces from one single view. Thermal radiations emitted by the hot liquid metal at a wavelength within the arc plasma blind spectral window are acquired by a wavefront division polarimetric system. The refractive index of the liquid metal and the topography of the weld pool surface are inferred from the polarimetric state of the thermal radiations.

Ultrathin high-index metasurfaces for shaping focused beams

2015

The volume size of a converging wave, which plays a relevant role in image resolution, is governed by the wavelength of the radiation and the numerical aperture (NA) of the wavefront. We designed an ultrathin (λ/8 width) curved metasurface that is able to transform a focused field into a high-NA optical architecture, thus boosting the transverse and (mainly) on-axis resolution. The elements of the metasurface are metal-insulator subwavelength gratings exhibiting extreme anisotropy with ultrahigh index of refraction for TM polarization. Our results can be applied to nanolithography and optical microscopy. Spanish Ministry of Economy and Competitiveness (MEC) (TEC2013-50416-EXP).

Properties of silicon integrated photonic lenses: bandwidth, chromatic aberration, and polarization dependence

2013

We analyze the properties of silicon integrated photonic lenses based on scattering optical elements. The devices have been inverse- designed by combining genetic algorithms and the multiple scattering theory. These lenses are able to focus an infrared plane wave front on a position freely determined during the design stage. The nanofabricated silicon integrated lenses have proved effective over a large range of wave- lengths, measured to be of the order of 100 nm. The lenses show chromatic aberration, with a displacement of the position of the focus mea- sured to be higher than 1.5 μm when the wavelength varies from 1500 to 1600 nm. Moreover, we analyze the polarization of the focused beam…

Transmission-line model to analyze a multistage polarizer rotator

1991

A simple transmission-line model to design a broadband system consisting of a multilayered polarization rotator that rotates the polarization plane of a linearly polarized electromagnetic wave is presented. A simulation program that permits the design of the rotator parameters was implemented, and a prototype was designed, manufactured, and tested. Comparisons between the theoretical results and measurements are given, and a good correspondence is found.

Molecular polarizability of Scn, Cn and endohedral Scn@Cm clusters

2002

The interacting induced dipoles polarization model implemented in the program POLAR is used for the calculation of the molecular dipole-dipole polarizability . The method is tested with Sc1-Sc7, Sc12, Sc17, Sc74, C, C12, C60, C70, C82-fullerene, Sc@C60, Sc@C82, Sc2@C82, Sc3@C82, C1-C6, C10, C13, C16, C19, C22, C24, C42, C54, C84 and C96-graphite clusters. The polarizability is an important quantity for the identification of clusters with different numbers of atoms and even for the separation of isomers. The results for the polarizability are of the same order of magnitude as reference calculations performed with another program based on the same formulation. The bulk limit for the polarizab…