GHz acousto-optic angular momentum with tunable topological charge.

Controlling the symmetry of optical and mechanical waves is pivotal to their full exploitation in technological applications and topology-linked fundamental physics experiments. Leveraging on the control of orbital angular momentum, we introduce here a device forming acoustic vortices which can impart an orbital angular momentum modulation at super-high-frequency on reflected light beams. Originated by shape-engineering of a single-contact bulk acoustic wave resonator, acoustic vortices are generated in a wide band of frequencies around 4 GHz with topological charge ranging from 1 to beyond 13 tunable by the device geometry and/or excitation frequency. With all electrical control and on-chip integration our device offers compact solutions for angular-momentum-based light communication, three-dimensional particle manipulation, as well as alternative interaction schemes for optomechanical devices.