Generation of Multi-Mode OAM Waves Through Programable 2-Bit Digital Coding Metasurfaces.

A programable 2-bit digital coding metasurfaces (DCMS) is presented for the generation of multi-mode converged orbital angular momentum (OAM) waves. The designed DCMS consists of reconfigurable units with 2-bit phase modulation through introducing a voltage-controlled varactor diode to change the unit resonant property. By digitally varying the coding distribution on the metasurfaces, the converged multi-mode OAM beams can be generated.