Non-separable Optical Beam Shifts and Emergence of Position-position Classical entanglement

TL;DR

This paper demonstrates that optical beam shifts at interfaces are inherently non-separable, leading to a form of classical entanglement between position variables, with potential applications in optical metrology and quantum-inspired technologies.

Contribution

It reveals the non-separability of longitudinal and transverse beam shifts as a classical entanglement, providing new insights into wave interference effects at interfaces.

Findings

Non-separability of beam shifts is significant in specific parameter regions.

Position-position classical entanglement can be controlled via experimental parameters.

The phenomenon enriches understanding of wave packet interference and beam shift physics.

Abstract

Under the introduction of any interface in its trajectory, an optical beam experiences polarization-dependent deflections in the longitudinal and transverse directions with respect to the plane of incidence. The physics of such optical beam shifts is connected to profound universal wave phenomena governed by the fine interference effects of wave packets and has opened up avenues towards metrological applications. Here, we reveal the inherent non-separability of the longitudinal and transverse beam shifts by considering a rather simple case of a partially reflecting Gaussian laser beam from a dielectric interface. This non-separability appears substantially in some particular regions in the corresponding parameter space. We further show that such non-separability manifests as a position-position classically entangled state of light. The tunability of the related experimental parameters offers control over the degree of entanglement. Uncovering of the inherent non-separability of the two types of beam shifts is expected to enrich the physical origin of this fundamental effect, impact the understanding of numerous analogous effects, and might find useful applications by exploiting the position-position-polarization classical entanglement in a fundamental Gaussian beam.