Optical vortex beams with controllable orbital angular momentum using an optical phased array

Laser beams with orbital angular momentum (OAM) have applications ranging from optical communications to quantum optics. However, the generation of OAM beams, particularly with variable OAM order, remains a challenge. We demonstrate, for the first time, the generation of OAM beams with variable OAM order using an optical phased array (OPA). OPAs are a multi-emitter solid-state device able to manipulate the distribution of optical power in the far field by controlling the relative phase of individual emitters. By applying an azimuthal phase offset to a hexagonal arrangement of laser emitters, we are able to generate OAM beams and change the OAM order easily and rapidly. This method is scalable to hundreds of emitters and GHz rate phase modulation.