Laboratory of Artificial Intelligence Nanophotonics and Centre for Ultrahigh Bandwidth Devices for Optical Systems (CUDOS), School of Science, RMIT University, Melbourne, Victoria 3000, Australia

In optics, the possibility of manipulation of optical angular momentum at the nanoscale is of crucial importance for both fundamental research and many emerging applications. However, it is still fundamentally challenging to achieving on-chip angular momentum multiplexing due to the extrinsic nature of orbital angular momentum associated with a helical wavefront. Here we present an entirely new concept of nanoplasmonic multiplexing of angular momentum through the nonresonant angular momentum mode-sorting sensitivity by nanoring slit waveguides on tightly-confined plasmonic angular momentum modes, leading to on-chip angular momentum multiplexing of ultra-broadband light ranging from the visible to terahertz regions.