title: Active phase-nulling of the self-mixing phase in a terahertz frequency quantum cascade laser.
abstract: We demonstrate an active phase-nulling scheme for terahertz (THz) frequency quantum cascade lasers (QCLs) under optical feedback, by active electronic feedback control of the emission frequency. Using this scheme, the frequency tuning rate of a THz QCL is characterized, with significantly reduced experimental complexity compared to alternative approaches. Furthermore, we demonstrate real-time displacement sensing of targets, overcoming the resolution limits imposed by quantization in previously implemented fringe-counting methods. Our approach is readily applicable to high-frequency vibrometry and surface profiling of targets, as well as frequency-stabilization schemes for THz QCLs.
authors.forename: P
authors.initials: P
authors.lastname: Dean
authors.forename: J
authors.initials: J
authors.lastname: Keeley
authors.forename: A
authors.initials: A
authors.lastname: Valavanis
authors.forename: K
authors.initials: K
authors.lastname: Bertling
authors.forename: Y L
authors.initials: YL
authors.lastname: Lim
authors.forename: T
authors.initials: T
authors.lastname: Taimre
authors.forename: R
authors.initials: R
authors.lastname: Alhathlool
authors.forename: L H
authors.initials: LH
authors.lastname: Li
authors.forename: D
authors.initials: D
authors.lastname: Indjin
authors.forename: A D
authors.initials: AD
authors.lastname: Rakić
authors.forename: E H
authors.initials: EH
authors.lastname: Linfield
authors.forename: A G
authors.initials: AG
authors.lastname: Davies