Detection of a spinning object with circular procession using an optical vortex beam

The rotational Doppler effect (RDE) provides an efficient way to measure rotational frequency using an optical vortex beam. Crucially, most research based on the RDE just involves a spinning object or a spinning object coupled with a longitudinal velocity along the beam propagation. We analyze the interaction mechanism between optical orbital angular momentum and a spinning object with circular procession and experimentally demonstrate simultaneous measurements of two rotational frequencies. This technique broadens application of the RDE in optical metrology and remote detection of targets with micro-motions.