title: Intersubband gain-induced dispersion.
abstract: Time-resolved transmission spectroscopy of a mid-infrared quantum cascade laser emitting at 11.7 mum allows us to iteratively retrieve the effective refractive index and the extinction coefficient of the gain medium in a broad spectral range with an accuracy of +/-7x10(-3). Besides a 3% slowdown of the group velocity we find a large induced group-velocity dispersion with changing signs in the vicinity of the gain maximum, disclosing implications for self-pulse formation in quantum-cascade lasers. Additionally we measured the temperature in the active region by exploiting the thermo-optic effect. A linear behavior with respect to the current and the duty cycle was observed.
authors.affiliation: Institute for Photonics, Vienna University of Technology, Vienna, Austria. wolfgang.parz@tuwien.ac.at
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Parz
authors.forename: Thomas
authors.initials: T
authors.lastname: Müller
authors.forename: Juraj
authors.initials: J
authors.lastname: Darmo
authors.forename: Maximilian
authors.initials: M
authors.lastname: Austerer
authors.forename: Gottfried
authors.initials: G
authors.lastname: Strasser
authors.forename: Luke
authors.initials: L
authors.lastname: Wilson
authors.forename: John
authors.initials: J
authors.lastname: Cockburn
authors.forename: Andrey
authors.initials: A
authors.lastname: Krysa
authors.forename: John
authors.initials: J
authors.lastname: Roberts
authors.forename: Karl
authors.initials: K
authors.lastname: Unterrainer