Tunable toroidal excitation in a reconfigurable terahertz metamaterial*

Compared with the traditional electric and magnetic multipolar excitation, the existence of a dynamic toroidal moment has received increasing interest in recent years due to its novel electromagnetic response. In this work, we present unique reconfigurable terahertz metamaterials where artificial toroidal metamolecules and traditional MEMS bi-material cantilever structures are integrated within the same unit cell. Through modification of the bending angle through thermal stimulus, the intensity of the toroidal moment increases by approximately 5 orders of magnitude. The toroidal excitation is measured using terahertz time-domain spectroscopy and confirmed numerically with a multipole decomposition method. Our results demonstrate the use of bi-material cantilevers to realize a tunable toroidal moment.