J. Phys. I France 7 (1997) 1211-1219
DOI: 10.1051/jp1:1997118

About Superluminal Propagation of an Electromagnetic Wavepacket Inside a Rectangular Waveguide

F. Cardone¹, R. Mignani^{2, 3} and V.S. Olkhovsky<sup>4

1</sup>  Università Gregoriana and GNFM-CNR, Piazza della Pilotta 4, 00187 Roma, Italy
²  Dipartimento di Fisica "E.Amaldi", Università degli Studi "Roma Tre", via della Vasca Navale 84, 00146 Roma, Italy
³  INFN, Sezione di Roma 1, c/o Dipartimento di Fisica, I Universitá degli Studi di Roma "La Sapienza", P.le A.Moro 2, 00185 Roma, Italy
⁴  Institute for Nuclear Research, Ukrainian Academy of Sciences, Prospect Nauki 47, 252028 Kiev, Ukraine

(Received 22 November 1996, revised 21 May 1997, accepted 9 June 1997)

Abstract
We discuss the propagation of an electromagnetic wavepacket inside a rectangular waveguide, of the type employed in recent experiments on superluminal tunneling of electromagnetic signals. By exploiting the analogy between particle and photon tunneling, we consider both evanescent and growing waves inside the narrowed part of the waveguide. The Fourier expansion of such waves shows that the barrier behaves in a nonlocal way. Such a nonlocality is accounted for in an effective way by means of a deformation of the spacetime inside the waveguide. As a consequence, the wavepacket propagates at superluminal speed according to an effective metric tensor, built up in analogy with the Cauchy stress tensor in a deformable medium.

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