Enhancement of light-matter interactions in slow-wave metasurfaces

We show that an ultrathin metamaterial can trap photons for a long time, with the measured longest trapping time being ∼5 ns for a microwave pulse with a center frequency of 5.5 GHz. Such photon-trapping effect is governed by the anomalous dispersion and surface plasmon excitations of the system, which is more significant in thinner samples owing to stronger mode hybridizations. Light-matter interactions are remarkably enhanced inside these structures, leading to perfect omnidirectional light absorption and dramatically enhanced nonlinear generations, which are demonstrated by microwave experiments and full-wave simulations.