Full-space orbital angular momentum generation using transmission-reflection-integrated coding metasurface

This study introduces an innovative design for transmission-reflection-integrated (TRI) space-coding metasurfaces, capable of generating high-purity orbital angular momentum (OAM) modes in the far-field and focusing lenses in the near-field within the same frequency band. The metasurfaces combine reflective and transmissive unit cells—gold patches on Teflon substrates—using a novel spatial coding scheme to create a unified structure. Various arrangements were explored and compared, demonstrating the metasurface's ability to simultaneously reflect and transmit OAM waves with high mode purity (undesired modes below 20 %) and focus waves with a narrow full-width half-maximum (FWHM) of less than 0.37 mm. Simulated at 0.662 THz, the design is adaptable to other frequency bands. The study outlines the design methodology, unit cell specifications, and analytical formulations, validated by full-wave simulations. These results underscore the potential of TRI coding metasurfaces for advanced electromagnetic wave control, with applications in wireless communication and wireless power transfer systems.