Probing the Electromagnetic Degree of Coherence of Light Beams with Nanoscatterers

Highly nonparaxial electromagnetic fields are increasingly met in modern nanophotonics. Their characterization is vital, but the traditional beam-field methods are not applicable. In this work we demonstrate a novel technique to measure the two-point electromagnetic spatial coherence of random beam fields based on scattering from dipolar nanoparticles. We consider both unpolarized and fully polarized beams. The resolution of the technique is limited by the size of the particles, and the results are shown to agree well with those obtained by a digital micromirror device. Nanoprobe detection of electromagnetic light fields is particularly relevant for near-field situations where polarization and coherence properties are of major importance.