Real-time measurement of transverse-mode-mixing effects in a Q-switched Nd:YAG laser

We describe a novel apparatus for the real-time characterization of transverse-mode-mixing effects by monitoring the fluctuations of the M(2) factor defined by Siegman Proc. Soc. Photo-Opt. Instrum. Eng. 1224, 2 (1990)]. A comparison between the results provided by our approach and those obtained by the use of a standard measurement apparatus has shown a satisfactory agreement within the experimental uncertainty.