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Plasmonic metastructures have become valuable platforms for manipulating light based on polarization. While traditional approaches have focused on sorting light through front- or back-scattering, recent advances underscore the potential of in-plane light routing—guiding and separating photons across the surface of the metastructure itself. In this study, we investigate how lateral asymmetry in nanoantenna design—introduced along the direction of in-plane light propagation rather than the axis of illumination—can be leveraged for efficient polarization sorting. We focus on metasurfaces composed of arrays of both symmetric and asymmetric gold nanoantennas. Our results reveal that such structural asymmetry enables two distinct modes of operation: in one, photons with different polarizations are directed along separate in-plane paths; in the other, they follow the same axis but are emitted at different angles depending on their polarization. We further examine the spectral dependence of this sorting behavior and demonstrate that asymmetric metastructures can realize four-way polarization sorting, each with unique anisotropic characteristics. Our simulation results provide insight into how phase modulation of the scattered light—coupled into the substrate beneath the metasurface—is influenced by nanoantenna asymmetry. These findings pave the way for compact, on-chip implementations of the planar spin Hall effect and for simplified metasurfaces suited to sensing, optical switching, and beam steering applications. 

We have demonstrated that plasmonic metasurfaces composed of arrays of Au bowtie nanoantennas can support an infrared bidirectional superscattering state. This state arises when the nanoantennas are coherently coupled together, forming a surface lattice resonance that efficiently guides the infrared range (1–1.6 μm) of incident broadband white light along the plane of the arrays. This process exhibits strong polarization dependence, offering an “OFF” state where a 90° rotation of the incident light polarization effectively suppresses in-plane scattering from all sides. Stokes parameters analysis is used to study the states of polarization of the scattering, demonstrating transformation into a complete depolarized state. The results emphasize the significant influence of the multipolar modes of these nanoantennas on the interference processes associated with such scattering phenomena, and their potential applications in polarization optical switching and unique beamsplitting. 

When a metallic U-shaped nanoantenna (split ring resonator) is observed from its sides, variations in the viewing angle can lead to significantly different size and shape projections. In this study, we demonstrate that plasmonic metasurfaces consisting of arrays of such nanoantennas can support unique side (in-plane) scattering switching and routing processes. These processes encompass a polarization switching centered at 1.6 μm, which is driven by the coherent excitation of the nanoantennas’ multipolar modes. They also include spectrally broadband (0.5–1.6 μm) directional control of the flow of in-plane light scattering. Such a process includes a total prohibition of light emerging from one side of the metasurface for a given polarization of the incident light. However, when such polarization is rotated by 90°, the flow of the in-plane scattering opens with high efficiency. We further discuss the impact of the formation of surface lattice resonance on the coherent amplification of infrared scattering around 1.6 μm and its switching process. The results underscore the influence of variations in asymmetry, associated with the sizes and shape projections, on interference processes. They also showcase how in-plane scattering has the capacity to transfer distinct characteristics of plasmonic near-field asymmetries induced by optical fields into far-field scattering.