Collective Resonances of Plasmonic Metasurfaces as an Experimental Platform for Nonlinear and Non-Hermitian Physics

Metasurfaces are two-dimensional arrays of coupled resonant nanostructures designed for controlling various aspects of light scattering and light emission. In our research, we focus on plasmonic metasurfaces composed of metallic nanoantenna arrays supporting dispersive lattice resonances. We present some theoretical and experimental advancements in combining these lattice resonances with active media, which include breaking parity-time symmetry in arrays with spatially engineered gain and loss. We develop an experimental method based on interferometric autocorrelation, targeting the investigation of resonant properties of such non-Hermitian systems by exploiting the enhancement of two-photon excited luminescence in the vicinity of plasmonic nanoantennas. Our findings reveal novel design strategies for distributed feedback lasing and active light shaping by resonant periodic nanostructures.