Invariance Properties and Measurement of Correlation Between Two Propagating or Evanescent Waves

ABSTRACT

We consider the strength of correlation between two propagating or evanescent, spatially coherent, plane waves, generally expressed in different frames. While for propagating waves the relevant correlation measure is obtained with traditional interferometric means, we demonstrate that for evanescent waves it can be found by employing a novel nanoscattering‐based procedure. We show theoretically and experimentally that the correlation measure remains invariant under unitary polarization changes and intensity scalings of propagating waves, as well as under the creation of evanescent waves in total internal reflection. These results provide new insights into the correlation properties of light fields and have potential applications in optical near‐field detection and sensing.