We report a high average power mid-infrared picosecond (ps) pulse bunch output by means of direct difference frequency generation (DFG) in periodically poled magnesium-doped lithium niobate between a linearly polarized ps pulse bunch Yb fiber laser and a synchronized Er fiber laser. The ps pulse bunch Yb fiber laser was composed of an all polarization maintained “figure of eight” structured mode-locked Yb fiber laser as the seed, a pulse multiplier, and two stages of Yb fiber amplifiers. The mode-locked Yb fiber laser has an output ps laser pulse at 1030 nm with a repetition rate of 16.32 MHz. The pulses were then transformed to the pulse bunches through the pulse multiplier. Within each bunch, there were 16 equally spaced pulses with pulse widths of 8.5 ps and time intervals around 300 ps. The Er fiber laser had a gain switched seed laser diode working at 1550 nm with a pulse width around 5.1 ns, which was synchronized to the mode-locked Yb fiber laser pulse bunch, and two stages of Er fiber amplifiers. Under the average power of 27.8 W of Yb fiber laser, we obtained an average output power of 3.1 W at 3.07 µm. This is, to the best of our knowledge, the highest average power mid-infrared ps pulse bunch obtained via DFG directly.

中文翻译：

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通过差频产生来产生大功率中红外皮秒脉冲束

我们报告了在线性极化ps脉冲束Yb光纤激光器和同步Er光纤激光器之间的周期性极化掺杂镁的铌酸锂中通过直接差频生成（DFG）方式输出的高平均功率中红外皮秒（ps）脉冲束。ps脉冲束Yb光纤激光器由全偏振保持的“八位数”结构锁模Yb光纤激光器作为种子，脉冲倍增器和两级Yb光纤放大器组成。锁模Yb光纤激光器的输出ps激光脉冲为1030 nm，重复频率为16.32 MHz。然后通过脉冲乘法器将脉冲转换为脉冲束。在每个束中，有16个等距脉冲，脉冲宽度为8.5 ps，时间间隔约为300 ps。fiber光纤激光器具有工作在1550 nm的增益切换种子激光二极管，其脉冲宽度约为5.1 ns，并与锁模Yb光纤激光器脉冲束同步，并具有两级stages光纤放大器。在Yb光纤激光器的平均功率为27.8 W的情况下，我们在3.07 µm处获得了3.1 W的平均输出功率。据我们所知，这是直接通过DFG获得的最高平均功率中红外ps脉冲束。