Reconfigurable dielectric resonators with imbedded impedance surfaces—From enhanced and directional to suppressed scattering

Abstract

Resonant elements play a vital role in tailoring of the radiation and scattering properties of devices, such as antennas and functional material platforms. We presently demonstrate a simple resonator that supports a multitude of scattering states. The resonator is a hybrid structure consisting of a finite-height dielectric cylinder integrated with a concentric impedance surface. Given its simple configuration, we apply the classical Lorentz–Mie theory to analyze its scattering properties analytically. Through a careful tuning of its geometry, the resonator is found to support enhanced and directive scattering states as well as the suppressed scattering states also known as anapole states. A prototype of the resonator has been built and tested at microwave frequencies. It utilizes water as the dielectric and a metallic tube with periodic slits as the impedance surface. Exploiting the flexibility of water, the design is easily reconfigured for different scattering responses: fully filled, the resonator is found to scatter predominantly in the forward direction, whereas an anapole state emerges with significant reduction of scattering when the resonator is partially filled with water. Consequently, the proposed resonator may be of great interest within the broad area of antenna design and functional material platforms, encompassing not only the obvious microwave frequencies but also the THz- and optical domain using high-permittivity dielectrics and graphene/nano-particle surfaces.