High-accuracy transverse translation velocimeter enabled by OAM-assisted dual-point transverse Doppler effect

Abstract

Laser Doppler velocimetry has developed as a powerful enabling technology within a myriad of realistic scenarios. While existing toolkits that exploit optical vortex allow access to longitudinal linear velocimetry and/or transverse rotational velocimetry of a motion object, achieving high-accuracy transverse translation velocimetry is still an open challenge. Here, we overcome this restriction by breaking the prevailing single-point metrological paradigm, instead employing dual-point transverse Doppler effect of customized orbital-angular-momentum (OAM) light fields as our pathway. We show that the dual-point transverse Doppler shifts can be generated and detected in a single velocimetry geometry for the first time, thereby enabling the determination of arbitrary transverse translation velocity. In particular, we demonstrate that the limited frequency resolution causes the velocimetry deviation and increasing the sampling duration can thus effectively improve velocimetry accuracy. As a consequence, a high-accuracy transverse translation velocimeter with a relative error below 0.08% has been well-established. Our validated findings not only provide a profound insight into the interaction of OAM with macroscopic motion object but also may find potential applications in clinical medicine, astronomical observation, and industrial manufacturing.