In this paper,we report a passively mode-locked Nd ∶Y3Sc2Al3O12[Nd∶YSAG]laser using a periodically poled LiNbO3[PPLN]superlattice.Nonlinear mirror mode locking based on PPLN intracavity frequency doubling was theoretically analyzed.The modulation depth of nonlinear reflectivity of the nonlinear mirror is approximately 8.8％.Optical performances of the mode-locked laser including output power,radio frequency spectrum,and optical spectrum were experimentally investigated.An average output power of 710 mW with a slope efficiency of 14.6％ was obtained at the pump power of 6.5 W.The repetition rate is 101.7 MHz,and the signal-to-noise ratio of the mode-locked pulse is 45 dB.The mode-locked pulse width was approx-imately 9 ps.