Actively tunable toroidal response in microwave metamaterials

Abstract

Toroidal dipole moment has attracted much attention in recent years due to their novel electromagnetic response such as non-reciprocal interactions and unusual low-radiating manifestations. However, most of the previously reported toroidal dipole moment are incapable of real-time control of direction and intensity. In this paper, an actively tunable toroidal metamaterials are proposed to achieve programmable toroidal dipole manipulations with electric control. The intensity and direction of toroidal dipole can be sensitively regulated by electrically controlling the loaded diodes. Our proof-of-concept experiments show that the toroidal dipole could be dynamically switched to the electric and magnetic dipole. Meantime, the direction of toroidal dipole also could be controlled. Experimental and numerical results, in good agreement, demonstrate good performance of the proposed toroidal metamaterials, with potential applications in modulators, sensors, and filters.