▎ 摘　　要

Yb:YGG, Yb:LuGG and Yb:CNGG compact diode-pumped lasers at 977 nm are passively Q-switched by a CVD-grown single layer graphene saturable absorber. With Yb:CNGG crystal, 190 ns/1.9 mu J pulses are generated at a repetition frequency of 235 kHz. This represents the highest pulse energy extracted from any graphene Q-switched Yb laser. The maximum average output power is 440 mW at 1045.1 nm with 24 % slope efficiency. With the Yb:YGG laser, the maximum output power reaches 462 mW at 1039.8 nm and the Q-switching conversion efficiency is as high as 55 %. Graphene is promising for generation of nanosecond pulses in Q-switched bulk Yb lasers at the frequencies approaching the MHz range.