Propagation speed of evanescent modes
The group velocity of evanescent waves (in undersized waveguides, for instance) was theoretically predicted, and has been experimentally verified, to be superluminal (v(g)>c). By contrast, it is known that the precursor speed in vacuum cannot be larger than c. In this paper, by computer simulations based on Maxwell equations only, we show the existence of both phenomena. In other words, we verify the actual possibility of superluminal group velocities, without violating the so-called (naive) Einstein causality.
Barbero
AP
DMO, FEEC, Universidade Estadual de Campinas, Campinas, SP, Brazil and TET, CTC, Universidade Federal Fluminense, RJ, Brazil.
Hernandez-Figueroa
HE
Recami
E