Scattering of Light with Orbital Angular Momentum from a Metallic Meta-Cylinder with Engineered Topological Charge

Planar metasurfaces with phase gradient exhibit unprecedented abilities in freely controlling light propagation. On the other hand, only a few studies have been devoted to unveiling the light scattering properties of cylindrical metasurfaces. Here we propose and study a metallic cylinder with a phase gradient obtained by engineering the gradient of grooves on its outer surface. We find that structural topological charges may be generated by the phase gradient in the meta-cylinder that, in turn, may be exploited to manipulate light scattering with orbital angular momentum (OAM) and obtain a new conservation law for OAM. Remarkably, at variance with results obtained by conventional core-shell structures, high-efficiency and multichannel OAM conversion/absorption may be realized with a single meta-cylinder, as we prove by theoretical analysis and numerical simulations. Moreover, owing to the transition of the diffraction channel and Ohmic loss in metal, asymmetric response to light is observed for incident OAM with opposite helicity. Our results open up a new train of thought for manipulating light scattering with OAM and pave the way to further versatile applications involving the manipulation of OAM with meta-objects.

Automated summary

This study introduces a metallic cylinder with a phase gradient obtained by engineering the gradient of grooves on its outer surface, demonstrating its ability to manipulate orbital angular momentum (OAM) through structural topological charges and achieve high-efficiency OAM conversion/absorption, while also observing asymmetric response to incident light with opposite OAM helicity.