title: Broadband terahertz amplification in a heterogeneous quantum cascade laser.
abstract: We demonstrate a broadband terahertz amplifier based on ultrafast gain switching in a quantum cascade laser. A heterogeneous active region is processed into a coupled cavity metal-metal waveguide device and provides broadband terahertz gain that allows achieving an amplification bandwidth of more than 500 GHz. The temporal and spectral evolution of a terahertz seed pulse, which is generated in an integrated emitter section, is presented and an amplification factor of 21 dB is reached. Furthermore, the quantum cascade amplifier emission spectrum of the emerging sub-nanosecond terahertz pulse train is measured by time-domain spectroscopy and reveals discrete modes between 2.14 and 2.68 THz.
authors.forename: Dominic
authors.initials: D
authors.lastname: Bachmann
authors.forename: Norbert
authors.initials: N
authors.lastname: Leder
authors.forename: Markus
authors.initials: M
authors.lastname: Rösch
authors.forename: Giacomo
authors.initials: G
authors.lastname: Scalari
authors.forename: Mattias
authors.initials: M
authors.lastname: Beck
authors.forename: Holger
authors.initials: H
authors.lastname: Arthaber
authors.forename: Jérôme
authors.initials: J
authors.lastname: Faist
authors.forename: Karl
authors.initials: K
authors.lastname: Unterrainer
authors.forename: Juraj
authors.initials: J
authors.lastname: Darmo