On the apparent superluminality of evanescent waves.

There have been many recent theoretical and experimental reports on the propagation of light pulses at speeds exceeding the speed of light in vacuum $c$ within media with anomalous dispersion, either opaque or with gain. Superluminal propagation has also been reported within vacuum, in the case of inhomogeneous pulses. In this paper we show that the observations of superluminal and non-causal propagation of evanescent pulses under the conditions of frustrated internal reflection are only apparent, and that they can be simply explained employing an explicitly (sub)luminal causal theory. However, the usual one-dimensional approach to the analysis of pulse propagation has to be abandoned and the spatial extent of the incoming pulse along the directions normal to the propagation direction has to be accounted for to correctly interpret the propagation speed of these evanescent waves. We illustrate our theory with animations of the time development of a pulse built upon the Huygen's construction.

Scattering by a periodically corrugated interface between free space and a gyroelectromagnetic uniaxial medium.

Diffraction of plane waves by a corrugated grating made of a gyroelectromagnetic uniaxial material is set up by using the T-matrix formalism. The fully vectorial treatment presented here is limited in its range of applicability by the use of the Rayleigh hypothesis. The preferred axis of the anisotropic medium is considered parallel to the mean surface of the periodic interface between the medium and the free space. The analysis is exemplified numerically by calculations performed for sinusoidal gratings.

Phase behavior near total absorption by a metallic grating.

A bare metallic grating illuminated by a plane, S-polarized electromagnetic wave can completely absorb one of the diffracted orders. These strong absorptions have been reported to be accompanied by two different types of behavior. Here we calculate, by means of an exact differential method, the phase versus angle-of-incidence curves for cycloidal metallic gratings with different groove-depth-to-period ratios. We show that an algorithm based on the electromagnetic theory of gratings can account for the experimentally observed behavior in the vicinity of a resonant anomaly. We also show that this type of study provides additional information about the position of the zeros of the scattering matrix in the complex plane.