Structured transverse orbital angular momentum probed by a levitated optomechanical sensor

The momentum carried by structured light fields exhibits a rich array of surprising features. In this work, we generate transverse orbital angular momentum (TOAM) in the interference field of two parallel and counter-propagating linearly-polarised focused beams, synthesising an array of identical handedness vortices carrying intrinsic TOAM. We explore this structured light field using an optomechanical sensor, consisting of an optically levitated silicon nanorod, whose rotation is a probe of the optical angular momentum, which generates an exceptionally large torque. This simple creation and direct observation of TOAM will have applications in studies of fundamental physics, the optical manipulation of matter and quantum optomechanics. A new polarization structure of light is synthesized in a straightforward and robust way. The light field is probed using a levitated nanoparticle as a sensor. Optical angular momentum is used to control the particle in a novel way, with applications in sensing and quantum optomechanics.