Measurement of optical coherence structures of random optical fields using generalized Arago spot experiment

The optical coherence structures of random optical fields can determine beam propagation behavior, light–matter interactions, etc. Their performance makes a light beam robust against turbulence, scattering, and distortion. Recently, we proposed optical coherence encryption and robust far-field optical imaging techniques. All related applications place a high demand on precision in the experimental measurements of complex optical coherence structures, including their real and imaginary parts. Past studies on these measurements have mainly adopted theoretical mathematical approximations, limited to Gaussian statistic involving speckle statistic (time-consuming), or used complicated and delicate optical systems in the laboratory. In this study, we provide: a robust, convenient, and fast protocol to measure the optical coherence structures of random optical fields via generalized Arago (or Poisson) spot experiments with rigorous mathematical solutions. Our proposal only requires to capture the intensity thrice, and is applicable to any optical coherence structures, regardless of their type or optical statistics. The theoretical and experimental results demonstrated that the real and imaginary parts of the structures could be simultaneously recovered with high precision. We believe that such a protocol can be widely employed in phase measurement, optical imaging, and image transfer.