Calculation of the Spatio-Temporal Dynamics of Q-switched Yb³⁺:YAG Laser with an Unstable Cavity and a Super-Gaussian Mirror

A numerical simulation used to compute the spatio-temporal dynamics of pulse formation of diode-pumped Q-switched Yb:YAG laser is carried out. The model takes the laser amplification and gain saturation, the properties of the laser cavity, and the diffractive effects of the laser disc into account. The numerical calculation is performed for a confocal positive-branch unstable resonator with a super Gaussian coupling mirror. The simulation results show that the laser pulse starts from a Gaussian intensity distribution and becomes rapidly non-Gaussian. The corresponding beam quality M² factor is seen to vary approximately from 1.5 at the beginning of the formation of pulse to more than 10 in the tail of the pulse, with a value of 11.6 at the peak of the pulse.