Optical Orbital Angular Momentum Read-Out Using a Self-Assembled Plasmonic Nanowire

Abstract

Orbital angular momentum (OAM) has emerged as an important parameter to store, control, and transport information using light. Recognizing optical beams that carry OAM at the nanoscale and their interaction with subwavelength nanostructures has turned out to be a vital task in nanophotonic signal processing and communication. The current platforms to decode information from different OAM modes are mainly based on bulk optics and requires sophisticated nanofabrication procedures. Motivated by these issues, herein we report on the utility of chemically prepared, individual plasmonic nanowire for OAM read-out. Our method is based on pattern recognition of coherent light scattering from individual nanowires that can be used as direct read-outs of two parameters of an OAM beam: magnitude of topological charge and its sign. All the experimental observations related to pattern formation are corroborated by three-dimensional numerical simulations. Given that pattern formation and recognition are exhaustively utilized in various computational domains, we envisage that our results can be interfaced with machine-learning methods, wherein direct read-out of OAM signals can be performed without human intervention. Such methods may have a direct implication on chip-scale robotics and chiral nanophotonic interfaces.