High-Energy Q-Switched 1645-nm Er:YAG Laser With a Co 2+ :MgAl 2 O 4 Saturable Absorber

We demonstrate a high-energy, passively Q-switched Er:YAG laser with a Co2+:MgAl2O4 saturable absorber. Pumped by an Er-doped fiber laser, the Er:YAG laser generates 1645-nm pulses with the maximum pulse energy of 656 $\mu \text{J}$ and the pulse duration of less than 200 ns at a high repetition rate of 2.285 kHz. The output laser beam remains high beam quality with the maximum output power of 1.5 W. The horizontal and vertical M2 factors are measured to be 1.22 and 1.32, respectively.