Mapping of temporal coherence function for ultrafast lasers via statistical fringe analysis of reconstructed phase maps

A technique for generating two-dimensional temporal coherence maps for ultrafast lasers using statistical fringe analysis of reconstructed phase maps is demonstrated experimentally. A tilted mirror in a Michelson-type digital holographic setup was used as the test object with varying depth. Due to the short coherence of the ultrafast laser used, the recorded hologram and, subsequently, its reconstruction appeared only within a local area in the transverse plane. Traditional methods to evaluate one-dimensional coherence function by scanning the hologram contrast are tedious while methods that utilize reconstructed intensity maps are hampered by the presence of speckle noise. Our technique utilizes reconstructed phase maps and, with the aid of the statistical algorithm, facilitates precise determination of the two-dimensional coherence function. The technique is non-scanning, noise robust and can be used for real-time monitoring of the temporal coherence function of ultrafast lasers.