Electromagnetic focusing by zero orbital angular momentum system.

We report on the observation of the electromagnetic focusing effect of zero orbital angular momentum (OAM) after introducing the multi-grade OAM concept. It performs the same feature in the central area around the focal point, while the typical Airy disk is transformed into a vortical cloud pattern beside the central area. Quantized focusing phenomena are exhibited based on the periodicity of the OAM. These results were verified by simulation and experiments. Our method achieves an optical focusing theory through OAM manipulation, which can be applied in imaging, photoetching, and communication. Furthermore, it also provides an opportunity for energy harvesting from natural OAM materials. [ABSTRACT FROM AUTHOR]