title: Phase-locking to a free-space terahertz comb for metrological-grade terahertz lasers.
abstract: Optical frequency comb synthesizers have represented a revolutionary approach to frequency metrology, providing a grid of frequency references for any laser emitting within their spectral coverage. Extending the metrological features of optical frequency comb synthesizers to the terahertz domain would be a major breakthrough, due to the widespread range of accessible strategic applications and the availability of stable, high-power and widely tunable sources such as quantum cascade lasers. Here we demonstrate phase-locking of a 2.5 THz quantum cascade laser to a free-space comb, generated in a LiNbO(3) waveguide and covering the 0.1-6 THz frequency range. We show that even a small fraction (<100 nW) of the radiation emitted from the quantum cascade laser is sufficient to generate a beat note suitable for phase-locking to the comb, paving the way to novel metrological-grade terahertz applications, including high-resolution spectroscopy, manipulation of cold molecules, astronomy and telecommunications.
authors.affiliation: LENS, European Laboratory for NonLinear Spectroscopy, Via N. Carrara 1, Sesto Fiorentino (FI) I-50019, Italy. luigi.consolino@ino.it
authors.forename: L
authors.initials: L
authors.lastname: Consolino
authors.forename: A
authors.initials: A
authors.lastname: Taschin
authors.forename: P
authors.initials: P
authors.lastname: Bartolini
authors.forename: S
authors.initials: S
authors.lastname: Bartalini
authors.forename: P
authors.initials: P
authors.lastname: Cancio
authors.forename: A
authors.initials: A
authors.lastname: Tredicucci
authors.forename: H E
authors.initials: HE
authors.lastname: Beere
authors.forename: D A
authors.initials: DA
authors.lastname: Ritchie
authors.forename: R
authors.initials: R
authors.lastname: Torre
authors.forename: M S
authors.initials: MS
authors.lastname: Vitiello
authors.forename: P
authors.initials: P
authors.lastname: De Natale