We study the role of optical momenta in surface plasmon excitation by topological bi-gratings. We analyze plasmonic structures composed of rectangular apertures rotating in 2D space with given rates, which couple to specific plasmon trajectories. We experimentally demonstrate the control of plasmonic propagation through premeditated design of the gratings, which interact with linear, spin, and orbital angular momentum of light. We show that these trajectories can be selected purely through momenta modulation with numerous degrees of freedom for a given structure geometry. Moreover, it is shown that the symmetry of the final plasmonic distribution is defined by selecting specific rotation rates, and that it can be different from the original grating symmetry.

We study the localization of plasmonic modes on topological dislocations obtained by an abrupt change in the geometry of unit cells in a plasmonic metasurface comprised of a nanoscale array of rectangular apertures. We experimentally demonstrate mode localization in line defects and point singularities in the topology. These results are confirmed by numerical simulations of the near field distributions along the topology boundaries. We present structures with line dislocations supporting dark and bright modes. Moreover, we show that in structures with point dislocations the localization strength can be further manipulated by modifying the topological order of the structure.

Light–matter interactions in a chiral structure can induce strong polarization selectivity. Specifically, an optical activity in a form of polarization rotation and a circular dichroism may be controlled by the mirror symmetry breaking of the unit-cell geometry. We design and experimentally investigate plasmonic metasurfaces with a spatially varying chiral geometry and demonstrate how this architecture may lead to a geometric Berry phase. Our designed structure produces a polarization-dependent diffraction of nearly linear states. We experimentally examine the diffraction orders and show that they are topological in nature. Moreover, the influence of various geometrical factors is also investigated.

We experimentally show the excitation of surface plasmons by topologically protected diffraction from gratings with randomized periodicity. The structures are designed such that the plasmonic excitation is conditioned by the proper combination of the geometric and the dynamic phases. Accordingly, it is possible to obtain a precise interaction of the incident light signal and a specific plasmonic directional mode in a polarization dependent manner.

We study the localization of plasmonic modes on topological dislocations obtained by an abrupt change in the geometry of unit-cells in a plasmonic metasurface. We experimentally demonstrate mode localization in line defects and point singularities in the topology. These results are confirmed by numerical simulations of the near field distributions along the topology boundaries. We present structures with line dislocations supporting dark and bright modes. Moreover, we show that in structures with point dislocations the localization strength can be further manipulated by modifying the topological order of the structure.