Ma Wanzhuo, Wang Tianshu, Su Qingchao, Wang Furen, Zhang Jing, Wang Chengbo, Jiang Huilin
Opt Express. 2018 May 14;26(10):12514-12521. doi: 10.1364/OE.26.012514.
We propose and demonstrate the operation of Q-switched mode-locked square-wave pulses in a thulium-holmium co-doped fiber laser. By using a nonlinear amplifying loop mirror, continuous square-wave dissipative soliton resonance pulse is obtained with 4.4 MHz repetition rate. With the increasing pump power, square-wave pulse duration can be broadened from 1.7 ns to 3.2 ns. On such basis Q-switched mode-locked operation is achieved by properly setting the pump power and the polarization controllers. The internal mode-locked pulses in Q-switched envelope still keep square-wave type. The Q-switched repetition rate can be varied from 41.6 kHz to 74 kHz by increasing pump power. The corresponding average single-pulse energy increases from 2.67 nJ to 5.2 nJ. The average peak power is also improved from 0.6 W to 1.1 W when continuous square-wave operation is changed into Q-switched mode-locked operation. It indicates that Q-switched mode-locked operation is an effective method to increase the square-wave pulse energy and peak power.
我们提出并演示了铥钬共掺杂光纤激光器中调Q锁模方波脉冲的运转。通过使用非线性放大环形镜，获得了重复频率为4.4 MHz的连续方波耗散孤子共振脉冲。随着泵浦功率的增加，方波脉冲持续时间可从1.7 ns展宽至3.2 ns。在此基础上，通过适当设置泵浦功率和偏振控制器实现了调Q锁模运转。调Q包络内的锁模脉冲仍保持方波类型。通过增加泵浦功率，调Q重复频率可在41.6 kHz至74 kHz之间变化。相应的平均单脉冲能量从2.67 nJ增加到5.2 nJ。当从连续方波运转变为调Q锁模运转时，平均峰值功率也从0.6 W提高到1.1 W。这表明调Q锁模运转是提高方波脉冲能量和峰值功率的有效方法。
