Abstract

Radially polarized beams of light exhibit a feature known as classical entanglement, where the mode function of the beam has a non-factorisable mathematical structure similar to that of a maximally entangled bipartite state of two qubits in quantum mechanics [1,2,3,4]. In practice, classical entanglement amounts to an intrinsic correlation between the mode’s spatial and polarization degrees of freedom, implying that the spatial trajectory of an opaque object moving across the beam causes a modulation of the polarization state of the latter (Fig. 1). We propose and experimentally demonstrate a novel application of this concept to high-speed kinematic sensing by measuring polarization only. Because of this, the method overcomes the speed limitations imposed by the electronic read-out of spatial detector arrays such as CCDs, allowing spatial sensing with GHz temporal resolution. We experimentally demonstrate the method’s feasibility by tracking the motion of a mm-sized object solely using polarization data (Fig. 2).

© 2015 IEEE