  It is well known that a closed loop of magnetic dipoles can give rise to the
rather elusive toroidal moment. However, artificial structures required to
generate the necessary magnetic moments are typically optically large, complex
to make and easily compromised by the kinetic inductance at high frequencies.
Instead of using magnetic dipoles, we propose a minimal model based on just
three aligned discrete electric dipoles in which the occurrence of resonant
toroidal modes is guaranteed by symmetry. The advantage of this model is its
simplicity and the same model supports toroidal moments from the microwave
regime up to optical frequencies as exemplified by a three-antenna array and a
system consisting of three nano-sized plasmonic particles. Both the microwave
and high-frequency configurations exhibit non-radiating "anapoles". Experiments
in the microwave regime confirm the theoretical predictions.

Optics;Mesoscale and Nanoscale Physics