1.5-MHz repetition rate passively Q-switched Nd：YVO_4 laser based on WS_2 saturable absorber

A transmission-type tungsten disulfide（WS_2）-based saturable absorber（SA） is fabricated and applied to passively Q-switched Nd：YVO_4 laser.The WS_2 nanosheets are deposited on a quartz substrate by the vertical evaporation method.By inserting the WS2 SA into the plano-concave laser cavity,we achieve 153-ns pulses with an average output power of1.19 W at 1064 nm.To the best of our knowledge,both of them are the best results among those obtained by the Q-switched solid-state lasers with WS_2-based absorbers.The repetition rate ranges from 1.176 MHz to 1.578 MHz.As far as we know,it is the first time that MHz level Q-switched pulses have been generated in all solid state lasers based on low-dimensional materials so far.