Microwave seminar | 16 November 2020

Sergey
 
Tel Aviv University
Wire resonator as a broadband Huygens superscatterer
Abstract
Interference phenomena render tailoring propagation of electromagnetic waves by controlling phases of several scattering channels. Huygens element, being a representative example of this approach, allows 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 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 non-magnetic materials, this structure demonstrates a strong magnetic response appearing in dominating magnetic multipoles over electric counterparts. Moreover, we predict and observe very high-order magnetic hexadecapole (M16-pole) and magnetic triakontadipole (M32-pole) with quality factors, approaching 6,000. The experimental demonstration is performed at the low GHz spectral range. Our findings shed light on a simple approach for engineering compact and open electromagnetic devices (antennas, directional reflectors, refractors, etc.) able to tailor wave propagation in a broadband domain, concentrate strong magnetic field, and generate high-order magnetic multipoles.
Diana
 
ITMO University
Generalized Kerker effect in dielectric resonant antennas for enhanced backscattering modulation
Abstract
My talk will be devoted to the development of a subwavelength antenna model, which provides high efficiency of RFID tags. The key parameter to be optimized is the modulation of the backscattering signal. It will be demonstrated that combining high refractive index dielectric materials with tunable subwavelength resonators achieves efficient modulation of the signal scattered towards the source. The considered layered spherical structure supports Mie resonances, the interference between which leads to either amplification or decreasing of backscattering, known as the generalized Kerker effect.