Simple and Nondestructive On-Chip Detection of Optical Orbital Angular Momentum through a Single Plasmonic Nanohole

Optical orbital angular momentum (OAM) provides an additional dimension for photons to carry information in high-capacity optical communication. Although the practical needs have informed the generations of miniaturized devices to manipulate the OAM modes in various integrated platforms, it is still a challenge for on-chip OAM detection to match the newly developed compact OAM emitter and OAM transmission fiber. Here, we demonstrate an ultracompact device, i.e., a single plasmonic nanohole, to efficiently measure an optical beam’s OAM state in a simple and nondestructive way. The device size is reduced to a few hundreds of nanometers, which can be easily fabricated and installed in the current OAM devices. It is a flexible and robust way for in situ OAM monitoring and detection in optical fiber networks and long-distance optical communication systems. With proper optimization of the nanohole parameters, this approach could be further extended to discriminate the OAM information multiplexed in multiple wavelengths and polarizations.