The quantum cascade laser has evolved to be a compact, powerful source of coherent mid-infrared light; however, its fast gain dynamics strongly restricts the formation of ultrashort pulses. As such, the shortest pulses reported so far were limited to a few picoseconds with some hundreds of milliwatts of peak power, strongly narrowing their applicability for time-resolved and nonlinear experiments. Here we demonstrate an approach capable of producing near-transform-limited subpicosecond pulses with several watts of peak power. Starting from a frequency-modulated phase-locked state, ultrashort high-peak-power pulses are generated via spectral filtering, gain modulation-induced spectral broadening and external pulse compression. We assess their temporal nature by means of a novel asynchronous sampling method, coherent beat note interferometry and interferometric autocorrelation. These results open new pathways for nonlinear physics in the mid-infrared.

量子级联激光器已经发展成为一种紧凑、强大的相干中红外光源；然而，它的快速增益动态极大地限制了超短脉冲的形成。因此，迄今为止报告的最短脉冲仅限于几皮秒，峰值功率为数百毫瓦，大大缩小了它们在时间分辨和非线性实验中的适用性。在这里，我们展示了一种能够产生具有几瓦峰值功率的近变换限制的亚皮秒脉冲的方法。从调频锁相状态开始，通过频谱滤波、增益调制引起的频谱展宽和外部脉冲压缩产生超短高峰值功率脉冲。我们通过一种新颖的异步采样方法评估它们的时间性质，相干拍音干涉测量和干涉自相关。这些结果为中红外非线性物理开辟了新途径。