RESUMEN
Controlling and manipulating surface waves is highly beneficial for imaging applications, nanophotonic device design, and light-matter interactions. While deep-subwavelength structuring of the metal-dielectric interface can influence surface waves by forming strong effective anisotropy, it disregards important structural degrees of freedom such as the interplay between corrugation periodicity and depth and its effect on the beam transport. Here, we unlock these degrees of freedom, introducing weakly modulated metasurfaces, structured metal-dielectric surfaces beyond effective medium. We utilize groove-structuring with varying depths and periodicities to demonstrate control over the transport of surface waves, dominated by the depth-period interplay. We show unique backward focusing of surface waves driven by an umklapp process-momentum relaxation empowered by the periodic nature of the structure and discover a yet unexplored, dual-stage topological transition. Our findings can be applied to any type of guided wave, introducing a simple and versatile approach for controlling wave propagation in artificial media.
RESUMEN
Incorporating optical surface waves in nonlinear processes unlocks unique and sensitive nonlinear interactions wherein highly confined surface states can be accessed and explored. Here, we unravel the rich physics of modal-nonmodal state pairs of short-range surface plasmons in thin metal films by leveraging "dark nonlinearity"-a nonradiating nonlinear source. We control and observe the nonlinear forced response of these modal-nonmodal pairs and present nonlinearly mediated direct access to nonmodal plasmons in a lossless regime. Our study can be generalized to other forms of surface waves or optical nonlinearities, toward on-chip nonlinearly controlled nanophotonic devices.