Mode-locked short pulses from an 8 um wavelength semiconductor laser


Johannes Hillbrand, Nikola Opačak, Marco Piccardo, Harald Schneider, Gottfried Strasser, Federico Capasso, and Benedikt Schwarz. 2020. “Mode-locked short pulses from an 8 um wavelength semiconductor laser.” Nature Communications, 11, 1, Pp. 5788. Publisher's Version


Quantum cascade lasers (QCL) have revolutionized the generation of mid-infrared light. Yet, the ultrafast carrier transport in mid-infrared QCLs has so far constituted a seemingly insurmountable obstacle for the formation of ultrashort light pulses. Here, we demonstrate that careful quantum design of the gain medium and control over the intermode beat synchronization enable transform-limited picosecond pulses from QCL frequency combs. Both an interferometric radio-frequency technique and second-order autocorrelation shed light on the pulse dynamics and confirm that mode-locked operation is achieved from threshold to rollover current. Furthermore, we show that both anti-phase and in-phase synchronized states exist in QCLs. Being electrically pumped and compact, mode-locked QCLs pave the way towards monolithically integrated non-linear photonics in the molecular fingerprint region beyond 6 $μ$m wavelength.
Last updated on 12/26/2020