N.S. Almeida

Theory of far-infrared ATR from surface polaritons in an n-i-p-i superlattice

Abstract We have analysed the surface phonon plasmon polariton spectra in n-i-p-i superlattices using the far-infrared attenuated-total-reflection (ATR) spectroscopy. We have used a theoretical approach based on an effective-medium theory to describe the polarition dispersion relation. The ATR spectrum was calculated not only in the usual way, but also by considering the superlattice as a uniaxial medium. Numerical results are shown and their main features discussed.

Polaritons in hollow cylinders in the presence of a dc magnetic field

We study the effects of a dc external magnetic field on the polaritons propagating in hollow dielectric cylinders, taking into account the retardation effects. In solving Maxwells equations we show that only the TM modes can propagate in these systems, and we obtain the dispersion relation of the confined-surface-polariton modes. The effects of geometric parameters and the external magnetic field on the propagation of surface-polariton modes are also analyzed and show significant influence on the behavior of the modes. Numerical results are presented for the dispersion relation of surface polaritons with GaAs as the optically active medium.

On the entropy-fluctuation contribution to Rayleigh scattering of light ☆

Abstract We discuss the power spectrum due to entropy fluctuations near the surface for quasielastic Rayleigh scattering in isotropic crystals. A back-scattering, oblique incidence geometry, is used in our theoretical calculations. Some interesting novel aspects are presented and their importance is discussed.

Theory of light scattering by acoustic modes on liquids interfaces

A theory of light scattering from the surface of a highly opaque metallic liquid bounded by a transparent medium is developed using a linear response function theory. The light scattering cross section is calculated taking only the ripple mechanism into account in the two media. Two limit cases are also derived and it is shown that they are in agreement with previous theories. Numerical results are also presented and in particular it is shown that our theoretical spectrum is in good agreement with the experimental data.

Influence of entropy-fluctuation on the Rayleigh spectrum

We discuss the light scattering cross section due to entropy-fluctuation on the region of the central peak of the spectrum. A back-scattering oblique incidence geometry is used in our theoretical calculations which are based on the linear response function approach. Our results show that the power spectrum varies significantly with the incident angle and frequency and so does the light scattering cross section. The results are illustrated with numerical calculations for silicon.

Influence of a Magnetic Field on the Energy Flow of Surface Polaritons Propagating in Semiconductor Cylinders

This work reports the influence of a dc external magnetic field on the polaritons propagating in cylindrical systems. We present numerical results for the dispersion relation and energy flow for surface polaritons modes propagating in hollow and massive cylinders made of GaAs and InSb.

On the physical behavior of magnetic ribbons

Abstract The frequency dependent magnetic susceptibility of an infinite ribbon is calculated. The ribbon is modeled by a collection of unit cells, which have two interacting domains of width l and length 2 D in the longitudinal direction. The domains are separated by a planar wall located at the position that gives the minimum value for the magnetic energy. The parameters used to describe the anisotropy and the interaction between the domains are related with the strength of the d.c. magnetic fields that saturate the magnetization in the transverse and longitudinal directions. We use the expression obtained for the susceptibility to study the behavior of the magnetoimpedance of these systems, and the result reproduces qualitatively the main features of the experimental data observed for some soft ferromagnetic ribbons.

Influence of nonlinearities on the pass band structure of magnetic superlattices

We consider superlattices constructed with alternate layers of antiferromagnetic and nonmagnetic materials to study the effect produced by the first nonlinear correction of the susceptibility of the antiferromagnetic material, on the electromagnetic pass bands of these artificial structures. We focus specially on the modifications produced on the pass band edges, as compared to the behavior exhibited under very low magnetic fields. Applications are made for FeF2/ZnF2 superlattices with different thicknesses.

Surface-ripple Brillouin scattering by Stoneley waves

Abstract The theoretical spectrum of Brillouin scattering by Stoneley waves and its limit case, which corresponds to the Brillouin lineshapes by Rayleigh waves, are shown and compared with recent experimental results for Molybdenum film. We show that there is excellent agreement between our theoretical predictions and the recent experimental measurements.

Light scattering by surface ripples on solid-liquid interface☆

Abstract We present a theory of light scattering from the surface of a viscous liquid bounded by a transparent crystal. The method of calculation takes into account the surface-ripple mechanism for the cross section, suitable for this kind of problem. Particular results are inferred from the main expressions, which recover previous theory. Also numerical calculations are presented and compared with other works.