title: Precisely tunable continuous-wave terahertz source with interferometric frequency control.
abstract: We realized a tunable continuous-wave terahertz source with megahertz frequency resolution. The system is based on optical heterodyning of two near-infrared distributed feedback diode lasers, each laser being stabilized by electronic feedback from a low-finesse quadrature interferometer. The control loop permits precisely linear laser frequency scans over >1200 GHz, and a beat signal linewidth of 1 MHz at 80 ms time scale. Using GaAs photomixers and log-periodic antennae, we achieve a signal-to-noise ratio of the terahertz power of >70 dB at 100 GHz and 100 ms integration time, and still approximately 30 dB at 1 THz. As an example for high-resolution terahertz spectroscopy, we characterize the transmission properties of a subwavelength metal grating.
authors.affiliation: TOPTICA Photonics AG, Lochhamer Schlag 19, D-82166 Gräfelfing, Germany.
authors.forename: Anselm J
authors.initials: AJ
authors.lastname: Deninger
authors.forename: Thorsten
authors.initials: T
authors.lastname: Göbel
authors.forename: Daniel
authors.initials: D
authors.lastname: Schönherr
authors.forename: Thomas
authors.initials: T
authors.lastname: Kinder
authors.forename: Axel
authors.initials: A
authors.lastname: Roggenbuck
authors.forename: Markus
authors.initials: M
authors.lastname: Köberle
authors.forename: Frank
authors.initials: F
authors.lastname: Lison
authors.forename: Thomas
authors.initials: T
authors.lastname: Müller-Wirts
authors.forename: Peter
authors.initials: P
authors.lastname: Meissner