title: Dynamics of actively mode-locked Quantum Cascade Lasers.
abstract: The impact of upper state lifetime and spatial hole burning on pulse shape and stability in actively mode locked QCLs is investigated by numerical simulations. It is shown that an extended upper state lifetime is necessary to achieve stable isolated pulse formation per roundtrip. Spatial hole burning helps to reduce the pulse duration by supporting broadband multimode lasing, but introduces pulse instabilities which eventually lead to strongly structured pulse shapes that further degrade with increased pumping. At high pumping levels gain saturation and recovery between pulses leads to suppression of mode locking. In the absence of spatial hole burning the laser approaches single-mode lasing, while in the presence of spatial hole burning the mode locking becomes unstable and the laser dynamics does not reach a steady state anymore.
authors.affiliation: Department of Electrical Engineering and Computer Science and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: V-M
authors.initials: VM
authors.lastname: Gkortsas
authors.forename: C
authors.initials: C
authors.lastname: Wang
authors.forename: L
authors.initials: L
authors.lastname: Kuznetsova
authors.forename: L
authors.initials: L
authors.lastname: Diehl
authors.forename: A
authors.initials: A
authors.lastname: Gordon
authors.forename: C
authors.initials: C
authors.lastname: Jirauschek
authors.forename: M A
authors.initials: MA
authors.lastname: Belkin
authors.forename: A
authors.initials: A
authors.lastname: Belyanin
authors.forename: F
authors.initials: F
authors.lastname: Capasso
authors.forename: F X
authors.initials: FX
authors.lastname: Kärtner
mesh_terms: D003198:Computer Simulation; D004867:Equipment Design; D007259:Infrared Rays; D054023:Lasers, Semiconductor; D008962:Models, Theoretical; D055095:Optics and Photonics / Q000295:instrumentation* / Q000379:methods*; D012666:Semiconductors