Active mode locking of broadband Quantum Cascade lasers

Active mode-locking in broadband Quantum Cascade (QC) lasers with a repetition rate of about 14.3 GHz has been achieved through the modulation of the laser bias current. At low driving currents the active mode-locking in the broadband (QC) lasers resemble the active mode-locking in the single wavelength QC lasers, when at high driving currents the mode-locking properties are governed by the broad spectral gain of these lasers. 

At high bias currents the active modulation can excite and phase- locks Fabry-Perot modes across the entire gain spectrum in the spectral range between 6.7 and 7.4 micron. The broad spectral width of the actively mode-locked lasers demonstrates the potential for generating subpicosecond pulses, and the variation of the spectra with modulation frequency allows a direct measurement of the group refractive index dispersion as +9E-3 (1/micron).