Compact and powerful ultrafast light sources at high pulse repetition rates, based on mode-locked near infrared fiber lasers, are now widely available and are being used in applications such as frequency metrology, molecular spectroscopy, and laser micro-machining. The realization of such lasers in the mid-infrared has, however, remained a challenge for many years. Here we report a record-breaking three-stage fiber laser system that uses an Er-doped fluoride fiber as gain medium, delivering W-level few-cycle pulses at 2.8 µm at a repetition rate of 42.1 MHz. A fiber-based seed oscillator, cavity dispersion-managed by a pulse-stretcher, generates near-100-fs mid-infrared pulses with ${\gt}{110}\;{\rm nm}$ spectral bandwidth. These pulses are amplified to an average power of ${\sim}{1}\;{\rm W}$ in a chirp-engineered fiber amplifier, and then compressed to ${\sim}{16}\;{\rm fs}$ in a short length of highly nonlinear ZBLAN fiber, resulting in a more-than-octave-wide spectrum reaching from 1.8 µm to 3.8 µm with a total power of 430 mW.

中文翻译：

---

次两周期倍频程中红外光纤激光器

基于锁模近红外光纤激光器的紧凑，强大，高脉冲重复率的超快光源现已广泛使用，并被用于频率计量，分子光谱学和激光微加工等应用。然而，在中红外中实现这种激光器多年来一直是一个挑战。在这里，我们报道了一个创纪录的三级光纤激光器系统，该系统使用掺Er的氟化物光纤作为增益介质，以2.8 µm的频率以42.1 MHz的重复频率提供W级的几个周期脉冲。一种基于光纤的种子振荡器，由脉冲拉伸器进行腔色散管理，可产生具有$ {\ gt} {110} \; {\ rm nm} $光谱带宽的近100 fs的中红外脉冲。这些脉冲被放大到平均功率$ {\ sim} {1} \; {\ rm W} $在线性调频工程光纤放大器中，然后在短长度的高度非线性ZBLAN光纤中压缩为$ {\ sim} {16} \; {\ rm fs} $，从而产生超过八度的频谱从1.8 µm到3.8 µm，总功率为430 mW。