Wave Propagation in Pure-Time Modulated Step Media With Applications to Temporal-Aiming

Abstract

We analyze the propagation of an incident electromagnetic wave in a purely-time modulated medium. Precisely, we assume that the permeability is unchanged while the permittivity has a multiple-step profile in time and uniformly constant in space. For this, we use time-dispersive Lorenz's model with time-dependent plasma frequency with highly concentrated values near the centers of the steps' intervals. Under certain regimes linking the number of steps to the contrasts of the permittivity, we can generate effective permittivity having positive and high values on a finite interval of time which behaves as a 'wall' that kills the forward waves and keeps only the backward waves (i.e. enabling full reflection). But this happens if these high values are away from a discrete set. If these high values are close to the elements of this discrete set, then the effective medium behaves as a 'well' that absorbs all the forward waves and hence there is no backward waves (i.e. enabling full transmission). Such results are reminiscent to the 'wall' and 'well' effects known in the quantum mechanics theory.