Topological Transitions and Surface Umklapp Scattering in Weakly Modulated Periodic Metasurfaces.

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.

Nonlinear Forced Response of Plasmonic Nanostructures.

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.