Monolithic active mode locking of quantum cascade lasers

We demonstrate active mode locking of a high-speed 8 mu m quantum cascade laser in a monolithic configuration, at a repetition rate of 11.6 GHz. Evidence of mode locking is obtained from the measured optical spectra and corresponding interferograms, as well as from the power spectra of the photocurrent detected with a fast quantum-well infrared photodetector. An estimate for the pulse width of approximately 5 ps is inferred from the experimental results. Mode-locked operation is observed up to a maximum temperature of over 120 K. (C) 2000 American Institute of Physics. [S0003-6951(00)01628-4].