Spatial axial shearing common-path interferometer for natural light

A spatial axial shearing interferometer is proposed to obtain a mutual coherence function representing longitudinal spatial coherence of natural light. The modulation of the quadratic phase distribution displayed on a spatial light modulator generates a spatial axial shear without a radial one. Because the optical path lengths along the optical axis on the two paths are identical, the spatial axial shear can be greater than the coherence length derived by temporal coherence. Experimental results are given to confirm that the mutual coherence function obtained by the proposed interferometer has spatial distribution expected by the relation between coherence and diffraction formula. (C) 2020 Optical Society of America