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Abstract We study projection-enabled enhancement of asymmetric optical responses of plasmonic metasurfaces for photon-spin control of their far field scattering. Such a process occurs by detecting the light scattered by arrays of asymmetric U-shaped nanoantennas along their planes (in-plane scattering). The nanoantennas are considered to have relatively long bases and two unequal arms. Therefore, as their view angles along the planes of the arrays are changed, they offer an extensive range of shape and size projections, providing a wide control over the contributions of plasmonic near fields and multipolar resonances to the far field scattering of the arrays. We show that this increases the degree of the asymmetric spin-polarization responses of the arrays to circularly polarized light, offering a large amount of chirality. In particular, our results show the in-plane scattering of such metasurfaces can support opposite handedness, offering the possibility of photon spin-dependent directional control of energy routing. 

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.