Critical dimension metrology of a plasmonic photonic crystal based on Mueller matrix ellipsometry and the reduced Rayleigh equation.

A computationally efficient algorithm based on the reduced Rayleigh equation, combined with an optimization scheme, is used to accurately retrieve the morphological parameters of a two-dimensional plasmonic photonic crystal from angle-resolved spectroscopic Mueller matrix ellipsometric measurements. The numerical method is successfully tested against experimental data and gives morphological parameters consistent with SEM and AFM measurements.

Leaky surface electromagnetic waves on a high-index dielectric grating.

We show theoretically that the periodically corrugated surface of a high-index dielectric medium can support a leaky surface electromagnetic wave. This wave is bound to the surface in the vacuum, but radiates into the dielectric. Despite this radiative damping, the surface wave can have a long lifetime.

Numerical solutions of the Rayleigh equations for the scattering of light from a two-dimensional randomly rough perfectly conducting surface.

We present rigorous, nonperturbative, purely numerical solutions of the Rayleigh equations for the scattering of p- and s-polarized light from a two-dimensional randomly rough perfectly conducting surface. The solutions are used to calculate the reflectivity of the surface, the mean differential reflection coefficients, and the full angular distribution of the intensity of the scattered field. These results are compared with previously published rigorous numerical solutions of the Stratton-Chu equations, and very good agreement is found.

Satellite peaks in the scattering of light from the two-dimensional randomly rough surface of a dielectric film on a planar metal surface.

A nonperturbative, purely numerical, solution of the reduced Rayleigh equation for the scattering of p- and s-polarized light from a dielectric film with a two-dimensional randomly rough surface deposited on a planar metallic substrate, has been carried out. It is found that satellite peaks are present in the angular dependence of the elements of the mean differential reflection coefficient in addition to an enhanced backscattering peak. This result resolves a conflict between the results of earlier approximate theoretical studies of scattering from this system.

Characterization of nanostructured GaSb: comparison between large-area optical and local direct microscopic techniques.

Low energy ion-beam sputtering of GaSb results in self-organized nanostructures with the potential of structuring large surface areas. Characterization of such nanostructures by optical methods is studied and compared to direct (local) microscopic methods. The samples consist of densely packed GaSb cones on bulk GaSb, approximately 30, 50, and 300 nm in height, prepared by sputtering at normal incidence. The optical properties are studied by spectroscopic ellipsometry, in the range 0.6-6.5 eV, and with Mueller matrix ellipsometry in the visible range, 1.46-2.88 eV. The optical measurements are compared to direct topography measurements obtained by scanning electron microscopy, high resolution transmission electron microscopy, and atomic force microscopy. Good agreement is achieved between the two classes of methods when the experimental optical response of the short cones (<55 nm) is inverted with respect to topological surface information, via a graded anisotropic effective medium model. The main topological parameter measured was the average cone height. Optical methods are shown to represent a valuable characterization tool of nanostructured surfaces, in particular when a large coverage area is desirable. Because of the fast and nondestructive properties of optical techniques, they may readily be adapted to in situ configurations.

Electromagnetic wave scattering from conducting self-affine surfaces: an analytic and numerical study.

We derive an analytical expression for the scattering of an s-polarized plane wave from a perfectly conducting self-affine one-dimensional surface in the framework of the Kirchhoff approximation. We show that most of the results can be recovered by means of a scaling analysis. We identify the typical slope taken over one wavelength as the relevant parameter controlling the scattering process. We compare our predictions with direct numerical simulations performed on surfaces of varying roughness parameters and confirm the broad range of applicability of our description up to very large roughness. Finally we verify that a nonzero electrical resistivity, provided that it is small, does not invalidate our results.

Wave scattering from self-affine surfaces

Electromagnetic wave scattering from a perfectly reflecting self-affine surface is considered. Within the framework of the Kirchhoff approximation, we show that the scattering cross section can be exactly written as a function of the scattering angle via a centered symmetric Levy distribution for the general roughness amplitude, Hurst exponent and wavelength of the incident wave. Our prediction is supported by direct numerical simulations.

Random surfaces that suppress single scattering.

We present a method for numerically generating a one-dimensional random surface, defined by the equation x(3)=zeta(x(1)), that suppresses single-scattering processes in the scattering of light from the surface within a specified range of scattering angles. Rigorous numerical calculations of the scattering of light from surfaces generated by this approach show that the single-scattering contribution to the mean scattered intensity is indeed suppressed within that range of angles.

Dofetilide reduces the incidence of ventricular fibrillation during acute myocardial ischaemia. A randomised study in pigs.

OBJECTIVE: The aim was to investigate whether dofetilide, a new selective cardiac potassium channel blocker, would reduce the incidence of ischaemia induced ventricular fibrillation in closed chest pigs. METHODS: A randomised, blinded, and placebo controlled study was performed in 32 closed chest pigs with a body weight of 70-90 kg. The animals were given a dofetilide/placebo bolus of 25 micrograms.kg-1 over a 10 min period followed by a maintenance dose of 12.5 micrograms.kg-1.h-1 for the next 130 min. Electrocardiograms were recorded during sinus rhythm and during atrial pacing, before (t0) and 20 min (t20) after the beginning of drug treatment. Twenty minutes after the start of drug treatment, acute myocardial ischaemia was induced by inflation of a percutaneous transluminal coronary angioplasty (PTCA) balloon placed in the left anterior descending coronary artery proximal to the first diagonal branch. If ventricular fibrillation occurred during the 2 h ischaemia period the balloon was deflated and defibrillation attempted by dc shocks (360 joules) up to a maximum of 10 shocks. RESULTS: Basal characteristics for the dofetilide group (n = 16) and the placebo group (n = 16) were similar: body weight 76.1(SD 5.4) kg v 75.4(4.4) kg; heart weight 296(29) g v 302(43) g; and heart rate (RR interval) 854(261) ms v 800(307) ms. During atrial pacing 100 beats.min-1 the paced QT interval (QTp) measured at t0 in the dofetilide group and the placebo group were similar, at 335(36) ms v 330(31) ms, respectively. During drug treatment (t20) the QTp interval increased to 412(38) ms in the dofetilide group (p < 0.001) whereas a much smaller increase to 341(32) ms was observed in the placebo group (p < 0.05). The heart rate and ST elevation in the two groups were similar during coronary artery occlusion. During the 2 h ischaemic period, ventricular fibrillation occurred in 6/16 (38%) of the dofetilide treated pigs, and in 13/16 (81%) of the placebo treated pigs (p < 0.01). Defibrillation was successful in 5/6 (83%) and 6/13 (46%) of the animals, respectively (p = 0.3). CONCLUSIONS: Dofetilide significantly reduces the incidence of ischaemia induced ventricular fibrillation in closed chest pigs.