Guest Editorial Orbital Angular Momentum Photonics

The thirty-six papers in this special issue focus on orbital angular momentum photonics. It is well known that angular momentum carried by elementary particles can be categorized as spin angular momentum (SAM) and orbital angular momentum (OAM). Since the early 1900's, Poynting recognized that a particle, such as a photon, can carry SAM, which has only two possible states. However, only recently, in 1992, Allen et al. discovered that photons with helical phase fronts can carry OAM, which has infinite orthogonal states. Since its discovery, the OAM-carrying beam has gained increasing interest from many different research communities, including physics, chemistry, and engineering, enabling tremendous advances in fundamental theories, devices, and applications. Due to its unique characteristics, OAM Photonics has opened new possibilities in various applications, including micromanipulation, laser beam machining, nonlinear matter interactions, imaging, sensing, quantum cryptography and, classical communications. During the past decade OAM Photonics has grown tremendously, and the field has turned out to be an extremely prosperous research area. This Special Issue provides a snapshot on the latest state of the art for the OAM Photonics field.