Strong Coupling and Exceptional Points in Optically Pumped Active Hyperbolic Metamaterials

We investigate the interaction of light in gain-enhanced multilayered hyperbolic metamaterials in the strong interaction regime. Pumping the dye in the dielectric layers from inside the light cone, while emission occurs into the lower hyperbolic band outside the light cone, eases the problem of light incoupling. In the strong coupling regime both emission and absorption lines cause a distortion of the plasmonic modes due to Rabi splitting and a PT-symmetry-broken phase, with generation of exceptional points at loss–gain compensation frequencies. We derive a semiclassical model that describes these phenomena for finite and infinite devices in detail, requiring only the overlap factor and the complex frequencies of the dye transition and the optical mode.