About Superluminal Propagation of an Electromagnetic Wavepacket Inside a Rectangular Waveguide

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