Detection of electromagnetic degree of coherence with nanoscatterers: comparison with Young's interferometer

We show theoretically that the (spectral) electromagnetic degree of spatial coherence of a random, stationary light beam can be measured by using two dipolar nanoscatterers instead of aperture diffraction as in traditional Young's interferometer. The method is based on considering individually the correlation functions associated with the six polarization states that make up the coherence (two-point) Stokes parameters and observing separately the visibilities and the locations of the intensity fringes created by the interfering dipole fields, leading to a complete characterization of the beam's second-order spatial coherence. The novel technique, although introduced in this work for beams, paves the way toward the detection of spatial coherence in nonparaxial optical near-fields for which the use of nanoscatterers is necessary.