Monte Carlo Least-Squares Fitting of the Beam Propagation Factor M2

A new method for M-2 least-squares fitting using Monte Carlo technique is introduced. The laser beam parameters and the propagation factor M-2 are calculated according to the ISO 11146. The initial values of the fitted parameters are analytically calculated and simple relations are given. These relations use three experimental points of the laser beam at different positions. The Monte Carlo fitting algorithm converged rapidly for all the tested beam. The M-2 value of a diode pumped Nd:YVO4 laser was optimized. The best M-2 value was 1.08. This optimization was done by changing the pump spot size at the laser crystal. The best overlapping between the pump spot size and the TEM00 mode dimension resulted in the best M-2 value.