Computational model for simultaneous Q switching and mode-locking in a solid state laser with a saturable absorber

A numerical model of rate equations for a four-level solid state laser with Cr⁴⁺:YAG saturable absorber including excited state absorption ESA is presented. The cavity is divided into a large number of disks and the model is solved for each disk and its local corresponding photon flux. The flux array is shifted for each recurrence simulating the movement of photons inside the cavity during the round trip. This simulator can describe the mode-locking phenomenon and can be used to simulate simultaneous mode locking and Q switching with a saturable absorber.