title: Active mode locking of quantum cascade lasers in an external ring cavity.
abstract: Stable ultrashort light pulses and frequency combs generated by mode-locked lasers have many important applications including high-resolution spectroscopy, fast chemical detection and identification, studies of ultrafast processes, and laser metrology. While compact mode-locked lasers emitting in the visible and near infrared range have revolutionized photonic technologies, the systems operating in the mid-infrared range where most gases have their strong absorption lines, are bulky and expensive and rely on nonlinear frequency down-conversion. Quantum cascade lasers are the most powerful and versatile compact light sources in the mid-infrared range, yet achieving their mode-locked operation remains a challenge, despite dedicated effort. Here we report the demonstration of active mode locking of an external-cavity quantum cascade laser. The laser operates in the mode-locked regime at room temperature and over the full dynamic range of injection currents.
authors.affiliation: Department of Physics and Astronomy, The University of Sheffield, Sheffield S3 7RH, UK.
authors.forename: D G
authors.initials: DG
authors.lastname: Revin
authors.affiliation: Department of Physics and Astronomy, The University of Sheffield, Sheffield S3 7RH, UK.
authors.forename: M
authors.initials: M
authors.lastname: Hemingway
authors.affiliation: Department of Physics and Astronomy, Texas A&M University, College Station, Texas 77843, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Physics and Astronomy, The University of Sheffield, Sheffield S3 7RH, UK.
authors.forename: J W
authors.initials: JW
authors.lastname: Cockburn
authors.affiliation: Department of Physics and Astronomy, Texas A&M University, College Station, Texas 77843, USA.
authors.forename: A
authors.initials: A
authors.lastname: Belyanin