Mode-locking characteristics of all-solid-state mode-locked laser with graphene saturable absorber

According to saturable absorber function of two-level system and theoretical model of Q-switched mode locking, and combining with all-solid-state Yb:YAG laser, the characteristics of the saturable absorption of graphene which is varied with layers and the critical pump power of Q-switched mode locking have been studied numerically. It can be seen that the saturable fluence and modulation depth are proportional to the graphene layers. The critical pump power will decrease when the graphene layers, transmittance of output mirror, beam radius on graphene and cavity length decrease, and Q-switched mode locking becomes easier. The resonant beam radius and laser crystal length have an optimal value each, which can obtain minimum critical pump power.