Luo Hongyu, Liu Fei, Li Jianfeng, Liu Yong
Opt Express. 2018 Oct 1;26(20):26485-26494. doi: 10.1364/OE.26.026485.
We present a MHz level high repetition rate gain-switched Ho-doped fiber laser at 2.103 μm using a h-shaped mode-locked Tm-doped fiber laser as the pump, for the first time. A NPR mode-locked Tm-doped ring cavity was designed as the seed, which could generate h-shaped pulses at 1.985 μm with a fundamental repetition rate of 1.435 MHz. It had a pump-dependent ns scale pulse duration with an almost unchanged peak amplitude. Then its output power and pulse energy were significantly scaled to 3.92W and 2.71 μJ, respectively based on a one-stage Tm-doped fiber based amplifier. After that, the amplified pulses were fed to a linear cavity Ho-doped fiber laser formed by a HR FBG and a perpendicularly cleaved fiber end, resulting in stable gain-switched pulses at 2.103 μm with a repetition rate of 1.435 MHz, which marks the record of gain-switched fiber lasers in this spectral region. At this repetition rate, the maximum output power of 1.13 W and pulse energy of 0.79 μJ were achieved at a high slope efficiency of 75.4% with respect to its absorbed pump power, giving the shortest pulse duration of 10.8 ns. The results indicated that the h-shaped pulses were an alternative choice for high repetition rate gain-switching in an all-fiber configuration.
我们首次展示了一种以h形锁模掺铥光纤激光器作为泵浦源、波长为2.103μm的兆赫兹级高重复频率增益开关掺钬光纤激光器。设计了一个非线性偏振旋转锁模掺铥环形腔作为种子源，它能在1.985μm处产生基本重复频率为1.435MHz的h形脉冲。其脉冲持续时间在纳秒量级且与泵浦相关，而峰值幅度几乎不变。然后基于一级掺铥光纤放大器，其输出功率和脉冲能量分别显著放大至3.92W和2.71μJ。之后，将放大后的脉冲输入由一个高反射光纤布拉格光栅（HR FBG）和一个垂直切割的光纤端面构成的线性腔掺钬光纤激光器中，从而产生波长为2.103μm、重复频率为1.435MHz的稳定增益开关脉冲，这创下了该光谱区域增益开关光纤激光器的记录。在这个重复频率下，相对于吸收的泵浦功率，以75.4%的高斜率效率实现了1.13W的最大输出功率和0.79μJ的脉冲能量，给出了10.8ns的最短脉冲持续时间。结果表明，h形脉冲是全光纤配置中高重复频率增益开关的一种替代选择。
