The Direct Observation of Toroidal Dipole Response in a Three Antennas System at Microwave Regime

Abstract

As we know, a closed loop formed by magnetic dipoles will generate a toroidal dipole moment. In the prior study, some artificial structures were fabricated to generate toroidal moments. However, most of these structures are based on building a closed loop of magnetic dipoles which are difficult to realize in the nanoscale. In this paper, we simply use three parallel electric dipoles to produce toroidal moments at microwave regime instead of using magnetic dipoles. The advantage of this method is its simplicity and it is easy to realize at optical frequency regime. Both simulations and microwave experiments are performed to confirm the existence of the toroidal dipole mode in this system and we further conclude that the three-dipole configuration can generate toroidal moments from microwave frequencies all the way up to optical frequencies.