Wire resonator as a broadband Huygens superscatterer

摘要

Interference phenomena allow tailoring propagation of electromagnetic waves by controlling phases of several scattering channels. Huygens element, being a representative example of this approach, enables enhancement of the scattering from an object in a forward direction, while the reflection is suppressed. However, a typical resonant realization of Huygens element employs constructive interference between electric and magnetic dipolar resonances that makes it relatively narrowband. Here we develop the concept of a broadband resonant Huygens element, based on a circular array of vertically aligned near-field coupled metal wires. Accurate management of multipole interference in an electrically small structure results in directional scattering over a large bandwidth, acceding 10% of the carrier frequency. Being constructed from nonmagnetic materials, this structure demonstrates a strong magnetic response appearing in dominating magnetic multipoles over electric counterparts. Moreover, we predict and observe higher-order magnetic multipoles. including hexadecapole (M16-pole) and magnetic triakontadipole (M32-pole) with quality factors, approaching 6000. The experimental demonstration is performed at the low GHz. spectral range. Broadband Huygens elements can be employed in a set of practical applications, where compact electromagnetic devices for tailoring wave propagation are needed, i.e.. antenna devices, directional reflectors, and even solar cells, given that the concept is scaled to the optical frequency range.