Null-field radiationless sources

Abstract

It is shown that it is in principle possible to produce combined sources of polarization and magnetization that are not only radiationless but that have any (and sometimes several) of the four microscopic or macroscopic electromagnetic fields exactly zero. The conditions that such a "null-field radiationless source" must satisfy are derived, and examples are given for several cases. The implications for transformation optics and invisibility physics in general are discussed.

Revealing radiationless sources with multi-harmonic mantle cloaking

“…In 1973, five generalized theorems have been derived by Devaney and Wolf [1] in order to find radiationless current distributions as solutions of Maxwell's equations with nontrivial internal electric field configurations. Several research efforts followed to derive other peculiar configurations of radiationless sources in terms of internal null-electric (or magnetic) field [2], internal singular values of the electromagnetics fields forming embedded (optical bound) eigenstates [3] or internal interfering electromagnetic multipoles creating anapole modes [4][5][6][7]. Rather than considering specific conditions on internal total fields, the design of invisibility cloaks [8][9][10][11] has been performed by considering the external electromagnetic fields and imposing to zero the ideal scattered (electric or magnetic) energy associated to undesired radiation: this unique condition automatically guarantees the generation of internal nontrivial current distributions.…”

Null-field radiationless sources: comment

“…the above equation for E becomes homogeneous. That this really yields a null-field solution, can be verified via Green-function methods [1].…”

“…the above equation for E becomes homogeneous. That this really yields a null-field solution, can be verified via Green-function methods [1]. The expression (1), when written in a slightly more general form as (∂ 0 P + curl M), gives the total current density in matter when extraneous currents are omitted.…”

“…The recent interesting paper of Hurwitz and Gbur [1] deals with nonradiating sources -sources whose fields are limited to a finite region of space and exactly equal to zero outside this region. The topic is in itself old, with roots going back to Ehrenfest (1910).…”