Introducing phase variations in spatial coherence using dynamics of spatially incoherent source

The spatial coherence function has proven to be a highly effective tool for light field manipulation. Although there has been considerable research on the spatial statistics of light, further exploration is needed to understand the phase variations within the coherence function. This study employs theoretical analysis and experimental investigations to gain insights into the phase modulations of far-field spatial coherence that are solely due to the modulations of the spatially incoherent source. We could modify the phase of the coherence function at different rates between different pairs of points without changing its magnitude. A square-wave amplitude grating is used and moved parallel to its plane to modulate the source intensity distribution. The proposed scheme is experimentally verified using a common-path Sagnac radial-shearing interferometer. This source-modulated phase shift technique has potential applications in optical interferometry schemes that employ incoherent light.