Investigation of the coupling between tunable split-ring resonators

Abstract

Passive resonant metamaterials are limited by the narrow-band nature of the resonances they support. Here we show that by incorporating an active component into the structure of the commonly used split-ring resonator it is possible to tune the resonance frequency of this type of metamaterial atom. We make use of this tunability to examine the interaction between two resonators, one passive and one active, as the resonance frequency of the active resonator is swept through that of the passive resonator. The resultant modes of this coupled system exhibit an anticrossing and, by changing the separation between, and relative orientation of, the split-ring resonators, we investigate how the magnetic and electric coupling terms change. We find that the relative orientation of the resonators significantly effects the strength of the coupling. Through both structural and active tuning we are able to alter the relative sizes and signs of the coupling terms. We hope that the nature of these changes will be of use to those designing large actively tunable metamaterial systems.