Researchers at IFIMAC introduce crystal polaritons: hybrid excitations that emerge when the collective excitations of a periodic quantum-emitter array strongly couple to the resonant Bloch modes of a metasurface. The resulting system forms a polaritonic quantum metasurface—a cavity-QED platform in which periodic light and periodic quantum matter are treated on an equal footing.
To describe this interaction in an extended, lossy, and dispersive nanophotonic structure, the authors develop a reciprocal-space few-mode quantization based on macroscopic QED. At each in-plane momentum, this method maps the metasurface resonances experienced by the emitter array onto an effective cavity-QED Hamiltonian. They show that both plasmonic surface-lattice resonances and dielectric bound states in the continuum can reach the strong-coupling regime with only one emitter per unit cell.
As a proof of concept, the authors predict that the resonant nonlinearities inherited by crystal polaritons can generate directionally emitted entangled photon pairs with efficiencies many orders of magnitude higher than those of conventional nonlinear metasurfaces. These results establish polaritonic quantum metasurfaces as a promising platform for efficient light–matter interfaces and quantum photonic technologies. [Full Article]
