FDTD analysis of the tunneling and growing exponential in a pair of epsilon-negative and mu-negative slabs

摘要

Pairing together material slabs with opposite signs for the real parts oftheir constitutive parameters has been shown to lead to interesting andunconventional properties that are not otherwise observable for single slabs.One such case was demonstrated analytically for the conjugate (i.e.,complementary) pairing of infinite planar slabs of epsilon-negative (ENG) andmu-negative (MNG) media [A. Alu, and N. Engheta, IEEE Trans. Antennas Prop.,51, 2558 (2003)]. There it was shown that when these two slabs are juxtaposedand excited by an incident plane wave, resonance, complete tunneling, totaltransparency and reconstruction of evanescent waves may occur in thesteady-state regime under a monochromatic excitation, even though each of thetwo slabs by itself is essentially opaque to the incoming radiation. This maylead to virtual imagers with sub-wavelength resolution and other anomalousphenomena overcoming the physical limit of diffraction. Here we explore how atransient sinusoidal signal that starts at t = 0 interacts with such an ENG-MNGpair of finite size using an FDTD technique. Multiple reflections andtransmissions at each interface are shown to build up to the eventual steadystate response of the pair, and during this process one can observe how thegrowing exponential phenomenon may actually occur inside this bilayer.