▎ 摘　　要

The first Ho microchip laser passively Q-switched using a graphene-based saturable absorber is demonstrated based on a Tm,Ho:KLu(WO4)(2) crystal cut along the N-g-axis. A maximum average output power of 74 mW is extracted from the diode-pumped laser at 2061 nm with a slope efficiency of 4%. Pulses as short as 200 ns with an energy of similar to 0.2 mu J are obtained at a repetition rate of 340 kHz. The energy transfer (ET), F-3(4) (Tm3+) <-> I-5(7) (Ho3+) is studied, yielding ET parameters of P-28 = 1.69 and P-71 = 0.15 x 10(-22) cm(3) mu s(-1), revealing the strong prevalence of direct ET.