Observation of nonspecular effects for Gaussian Schell-model light beams

TL;DR

This study experimentally demonstrates how the spatial coherence of Gaussian Schell-model beams influences certain optical beam shifts, resolving a recent theoretical debate about their dependence on coherence.

Contribution

The paper provides experimental evidence showing that angular beam shifts depend on spatial coherence, while the spatial Goos-Hänchen shift remains unaffected, clarifying theoretical disagreements.

Findings

Angular Goos-Hänchen effect depends on spatial coherence.

Angular Imbert-Fedorov effect depends on spatial coherence.

Spatial Goos-Hänchen effect is independent of incoherence.

Abstract

We investigate experimentally the role of spatial coherence on optical beam shifts. This topic has been the subject of recent theoretical debate. We consider Gaussian Schell-model beams, with different spatial degrees of coherence, reflected at an air-glass interface. We prove that the angular Goos-H\"anchen and the angular Imbert-Fedorov effects are affected by the spatial degree of coherence of the incident beam, whereas the spatial Goos-H\"anchen effect does not depend on incoherence. Our data unambiguously resolve the theoretical debate in favour of one specific theory.