中文摘要：

报道了以拉锥光纤上的石墨烯作为可饱和吸收体的2μm被动调Q锁模掺铥光纤激光器，采用环形腔结构，研究了腔内脉冲随着抽运功率增加的演化过程，并最终得到了稳定的调Q锁模脉冲，当抽运功率达到390mW时，开始出现调Q状态，重复频率为19．5kHz。当抽运功率达到490mW时开始出现调Q锁模现象。调Q包络重复频率为30．2kHz，锁模脉冲重复频率为19．5MHz。当抽运功率达到610mW时，锁模脉冲会填满调Q包络，此时调Q包络重复频率为44．9kHz，锁模脉冲重复频率仍为19．5MHz。

英文摘要：

A passively 2 μm Q-switched mode-locked thulium-doped fiber laser by using graphene saturable absorber on tapered fiber is experimently demonstrated. The pulse evolution with the increase of the pump power is discussed in the experiment. Finally stable Q-switched mode-locked pulse is obtained. Stable Q-switched pulse trains occurr at 390 mW pump power and the repetition rate is 19.5 kHz. When the pump power increases to 490 mW, Q-switched mode-locked pulse can be obtained. The Q-switched frequency is recorded with a frequency of 30.2 kHz and the mode-locked frequency is 19.5 MHz. After increasing the pump power to 610 mW, the mode-locked pulses are filled up with the Q-switched envelope. The Q-switched frequency is 44.9 kHz and mode-locked frequency is still 19.5 MHz.