Time domain study of electromagnetic cloaks for wideband invisibility under transient illumination

In this paper, the transient behavior of wideband cylindrical electromagnetic cloaks is investigated, and potential applications and design guidelines for such devices are described. Since virtually all published studies on electromagnetic cloaking assume a time-harmonic steady-state excitation, there exists very little information on the transient response of such devices in the literature. We show that cloaks can be designed to defeat transients with bandwidths of over one octave, provided that these cloaks are immersed in media with sufficiently high relative permittivity and permeability, so that the use of dispersive materials with constitutive parameters less than unity can be avoided. Transient time domain simulation results for cylindrical cloaks realized by concentric isotropic shells are presented, demonstrating excellent transient behavior. Design guidelines and potential applications are also described.