Köttig F, Schade D, Koehler J R, Russell P St J, Tani F
Opt Express. 2020 Mar 30;28(7):9099-9110. doi: 10.1364/OE.389137.
Over the past years, ultrafast lasers with average powers in the 100 W range have become a mature technology, with a multitude of applications in science and technology. Nonlinear temporal compression of these lasers to few- or even single-cycle duration is often essential, yet still hard to achieve, in particular at high repetition rates. Here we report a two-stage system for compressing pulses from a 1030 nm ytterbium fiber laser to single-cycle durations with 5 µJ output pulse energy at 9.6 MHz repetition rate. In the first stage, the laser pulses are compressed from 340 to 25 fs by spectral broadening in a krypton-filled single-ring photonic crystal fiber (SR-PCF), subsequent phase compensation being achieved with chirped mirrors. In the second stage, the pulses are further compressed to single-cycle duration by soliton-effect self-compression in a neon-filled SR-PCF. We estimate a pulse duration of ∼3.4 fs at the fiber output by numerically back-propagating the measured pulses. Finally, we directly measured a pulse duration of 3.8 fs (1.25 optical cycles) after compensating (using chirped mirrors) the dispersion introduced by the optical elements after the fiber, more than 50% of the total pulse energy being in the main peak. The system can produce compressed pulses with peak powers >0.6 GW and a total transmission exceeding 66%.
在过去几年中，平均功率在100瓦范围内的超快激光器已成为一项成熟技术，在科学和技术领域有众多应用。将这些激光器进行非线性时间压缩至几个甚至单周期持续时间通常至关重要，但仍然很难实现，特别是在高重复率情况下。在此，我们报道了一种两级系统，用于将1030纳米掺镱光纤激光器的脉冲压缩至单周期持续时间，输出脉冲能量为5微焦，重复率为9.6兆赫兹。在第一阶段，激光脉冲通过在充氪单环光子晶体光纤（SR-PCF）中进行光谱展宽从340飞秒压缩至25飞秒，随后用啁啾镜实现相位补偿。在第二阶段，脉冲通过在充氖SR-PCF中进行孤子效应自压缩进一步压缩至单周期持续时间。通过对测量脉冲进行数值反向传播，我们估计光纤输出端的脉冲持续时间约为3.4飞秒。最后，在补偿（使用啁啾镜）光纤后光学元件引入的色散后，我们直接测量到脉冲持续时间为3.8飞秒（1.25个光学周期），总脉冲能量的50%以上位于主峰。该系统能够产生峰值功率>0.6吉瓦且总传输率超过66%的压缩脉冲。
