https://www.laserfocusworld.com/test-measurement/test-measurement/article/16548377/beam-profile-analysis-propagation-factor-quantifies-laser-beam-performance
BEAM-PROFILE ANALYSIS: Propagation factor quantifies laser beam performance | Laser Focus World
Comparing M2 of an actual laser beam to a pure TEM00 Gaussian beam allows beam-propagation characteristics to be accurately predicted.
beam profile analysisperformance focuspropagationfactorlaser