Measurements were made of the thermally induced distortions occurring in laser rods as a result of flash lamp heating. Time-resolved interferograms were obtained by placing the sample in a Mach-Zehnder interferometer and utilizing a Q-switched laser as the interferometer-illumination source. It was observed that significant distortions occur during the pumping pulse leading to diverging-lens effects in the sample rods.
S. D. Sims, A. Stein, and C. Roth, "Dynamic Optical Path Distortions in Laser Rods," Appl. Opt. 5, 621-626 (1966)