High-efficiency coupling and reshaping of surface plasmon with metasurfaces

Freely controlling the surface plasmon polaritons (SPPs) is always an issue of photonic researches. While traditional approaches to excite and reshaping SPPs are widely utilized for a long time, they still suffer from some inherent challenges, e.g., low-efficiency, limited functionalities and huge size. While gradient metasurfaces exhibit strong abilities to control electromagnetic waves, most of previous works are devoted to modulate far-field EM waves [1-3]. Meanwhile, some metasurfaces are proposed to either couple the SPPs [4-6] or control the wavefronts of SPPs [7, 8] with very high efficiency. However, the metadevice with these two distinct functionalities merged together are rarely reported. Here, we propose a new scheme to simultaneously excite and reshape the SPPs with a single meta-device. Moreover, the chirality of input propagating waves can be utilized as a flexible freedom to modulate the wavefronts of the excited SPPs [9, 10]. Moreover, the wavefronts of the excited SPPs can be flexibly modulated to the totally independent forms, e.g., surface plasmon focusing and deflection, by simply changing the polarizations of impinging light. Our idea is successfully demonstrated by full wave simulations and near-field experiments. Our work may stimulate many near-field related applications, e.g., SPP holograms, complex SPP beam generations, super resolution imaging, enhanced non-linear effect, and so on.