Photonic topological transitions for surface waves with resonant plasmonic metasurfaces: interplay between meta-atom...

The optical resonances of plasmonic metasurfaces can have a significant impact on the ability to control the light properties. In particular, resonant plasmonic metasurfaces exhibit photonic topological transitions, leading to sharp transformations in the topology of the isofrequency contours in reciprocal lattice space. For instance, elliptical contours can transform into hyperbolic ones, and vice versa, significantly altering the wavefront and properties of the propagating light. This transition is accompanied by the flat isofrequency contours corresponding to the canalization regime, which means the divergenceless and high-directional wave propagation. In this work, we investigate the formation and engineering of the photonic topological transitions and the related effects in the plasmonic metasurfaces based on gold nanopatches via the continuous transformation from isotropic to anisotropic cases. We study the impact of the induced anisotropy on the spectral positions and amplitudes of the surface conductivity resonances describing the metasurfaces leading to the emergence of hyperbolicity, near-field hot-spots and plasmon canalization. Particular attention is paid to a comparative analysis of the two anisotropy-inducing strategies, stretching the meta-atoms and stretching the lattice, in terms of functionality and fabrication of plasmonic resonant metasurfaces. Our findings emphasize the importance of using anisotropic resonant nanostructures for a plethora of photonic applications, especially in the area of the in-plane light management.