Wang, Christine Y.Kuznetsova, LyubaGkotsas, Vasileios‐MariosDiehl, LKaertner, Franz X.Belkin, Mikhail A.Belyanin, AlexeyLi, XiaofengHam, DonheeSchneider, HaraldGrant, PeterSong, C. Y.Haffouz, SoufienWasilewski, ZbigniewLiu, H. C.Capasso, Federico2009-12-012009-12-01Wang, Christine Y., Lyuba Kuznetsova, Gkotsas Vasileios‐Marios, Laurent Diehl, Franz X. Kaertner, Mikhail A. Belkin, Alexey Belyanin, Xiaofeng Li, Donhee Ham, Harald Schneider, Peter Grant, et al. 2009. Mode-locked pulses from mid-infrared quantum cascade lasers. Optics Express 17(15): 12929-12943.1094-4087http://nrs.harvard.edu/urn-3:HUL.InstRepos:3425949In this study, we report the unequivocal demonstration of midinfrared mode-locked pulses from quantum cascade lasers. The train of short pulses was generated by actively modulating the current and hence the gain of an edge-emitting quantum cascade laser (QCL). Pulses with duration of about 3 ps at full-width-at-half-maxima and energy of 0.5 pJ were characterized using a second-order interferometric autocorrelation technique based on a nonlinear quantum well infrared photodetector. The mode-locking dynamics in the QCLs was modeled based on the Maxwell-Bloch equations in an open two-level system. Our model reproduces the overall shape of the measured autocorrelation traces and predicts that the short pulses are accompanied by substantial wings as a result of strong spatial hole burning. The range of parameters where short mode-locked pulses can be formed is found.en-USJournal Article2009-12-0110.1364/OE.17.012929