Local reference beam holography can be used in conjunction with interferometry to determine the complex amplitude distribution in the output of CW and pulsed laser beams. A hologram is recorded of the laser wavefront with a locally generated reference beam from the laser beam to be measured. The wavefront is then reconstructed with a CW laser beam in the usual way. The modulus of the complex amplitude can be measured directly and the phase is measured by interfering the reconstructed wavefront with a uniform phase wavefront. If the laser output is partially coherent the possibility exists of extending this method to determining the mutual intensity function and the complex degree of coherence of the laser wavefront.
B. J. Thompson,
"Application Of Local Reference Beam Holography To The Study Of Laser Beam Parameters," Optical Engineering 13(4), 134347 (1 August 1974). https://doi.org/10.1117/12.7971720