Achieving tunable Kerker-type invisibility for a radiation-enhanced electrically small antenna.

Abstract

Low-temperature gaseous plasmas exhibit great potential in designing tunable and reconfigurable electromagnetic devices. In this paper, based on an overdense-underdense core-shell plasma structure, tunable Kerker-type invisibility for a radiation-enhanced electrically small antenna is achieved, where dominant scattering direction can be mutated between backward and forward while omnidirectional invisibility and signal enhancement are maintained. Moreover, by electromagnetic multipole decompositions, it is shown that the underdense outer plasma with a negative polarizability is able to weaken the strength and modulate the phase of the electric dipolar scattering component (a_{1}), while the magnetic dipolar term (b_{1}) nearly remains unchanged. Consequently, quasi-first and -second Kerker conditions are fulfilled near the cutoff band of a_{1}.