Spatial Coherence and Optical Beam Shifts

TL;DR

This paper experimentally investigates how the spatial coherence of light affects beam shifts upon reflection, finding that coherence influences angular shifts but not spatial shifts, clarifying a controversial theoretical issue.

Contribution

The study provides experimental evidence that spatial coherence impacts angular beam shifts but not spatial shifts, resolving a long-standing controversy.

Findings

Angular shifts depend on spatial coherence.

Spatial shifts are unaffected by coherence.

Experimental results clarify theoretical debates.

Abstract

A beam of light, reflected at a planar interface, does not follow perfectly the ray optics prediction. Diffractive corrections lead to beam shifts; either the reflected beam is displaced (spatial shift) and/or travels in a different direction (angular shift), as compared to geometric optics. How does the degree of spatial coherence of light influence these shifts? Theoretically, this has turned out to be a controversial issue. Here we resolve the controversy experimentally; we show that the degree of spatial coherence influences the angular beam shifts, while the spatial beam shifts are unaffected.