Complex spatial coherence measurement using phase-shifting wavefront-inversion interferometry

Abstract Accurate measurement of the spatial coherence function is critical for applications ranging from imaging to communication. However, accurate measurement of arbitrary complex spatial coherence function still remains a significant challenge. In this work, we present a phase-shifting wavefront-inversion and shearing interferometric technique which enables direct, noise-insensitive measurement of the complex cross-spectral density function for a very broad class of fields, which includes all spatially stationary fields and the physically most relevant class of spatially non-stationary fields. By integrating the phase-shifting technique with wavefront inversion interferometry, we implement an intensity difference protocol that eliminates all phase-insensitive noise, significantly enhancing measurement fidelity. Experimental results validate the method’s robustness and accuracy, demonstrating its applicability to both stationary and non-stationary fields, and extending its utility to single-photon-level measurements. This technique represents a promising tool for all coherence-driven applications.