Mid-infrared femtosecond pulses from a quantum cascade laser

In recent years, quantum cascade lasers have matured to become compact, powerful sources of coherent mid infrared light. Yet, the ultrafast carrier dynamics in these sources has so far restricted the formation of high intensity ultrashort pulses. In this work, we demonstrate the formation of similar to 630 fs QCL pulses with a peak power of similar to 4.3 W. We break the picosecond barrier in an approach similar to chirped pulse amplification, where we externally recompress the maximally chirped output of a quantum cascade laser frequency comb. Ultrashort pulse formation is confirmed with a novel asynchronous optical sampling technique. These results emphasise the potential of quantum cascade lasers also as sources for non-linear experiments in the mid-infrared.