Coupling of nanoantennas in loss-gain environment for application in active tunable metasurfaces

A generic model of two dissimilar antenna-type resonators coupled both via near-field and far-field and embedded in active gain and/or loss medium is considered. Conditions required for hitting the superscattering regime corresponding to the threshold of lasing emission operation are established. It is shown that modulation of the medium gain and losses level within realistic parameters is an efficient approach for implementation of tunability. This two-antenna setup can serve as an inspiration for the implementation of high-contrast tunable metasurfaces.