Revisitation of Extraordinary Young's Interference: from Catenary Optical Fields to Spin-Orbit Interaction in Metasurfaces

Extraordinary Young's interference is an anomalous phenomenon observed at metallic surface in 2004. The shrinkage of slit size into deep subwavelength scale introduces many novel effects that cannot be described by classic interference theory. In this paper, the Young's interference excited by subwavelength slits is investigated via rigorous Maxwell's equations. We reveal a universal spin-orbit interaction mechanism associated with the catenary optical fields in 2D isotropic metal-dielectric structures for the generation of optical vortex array and spin Hall effect. Based on the interference of vectorial vortex arrays with opposite topological charges, a simple yet powerful method for the fabrication of space-variant metasurfaces is proposed for the first time, which breaks the fundamental limit of traditional interference lithography. These results may provide numerous new perspectives on both the design of catenary metasurfaces and optical spin-controlled devices.