title: High density terahertz frequency comb produced by coherent synchrotron radiation.
abstract: Frequency combs have enabled significant progress in frequency metrology and high-resolution spectroscopy extending the achievable resolution while increasing the signal-to-noise ratio. In its coherent mode, synchrotron radiation is accepted to provide an intense terahertz continuum covering a wide spectral range from about 0.1 to 1 THz. Using a dedicated heterodyne receiver, we reveal the purely discrete nature of this emission. A phase relationship between the light pulses leads to a powerful frequency comb spanning over one decade in frequency. The comb has a mode spacing of 846 kHz, a linewidth of about 200 Hz, a fractional precision of about 2 × 10(-10) and no frequency offset. The unprecedented potential of the comb for high-resolution spectroscopy is demonstrated by the accurate determination of pure rotation transitions of acetonitrile.
authors.affiliation: 1] AILES Beamline, Synchrotron SOLEIL, l'Orme des Merisiers, Saint-Aubin, Gif-sur-Yvette 91192, France [2] Laboratoire de Physico-Chimie de l'Atmosphère, Université du Littoral Côte d'Opale, EA4493 CNRS, 189A Avenue Maurice Schumann, Dunkerque 59140, France.
authors.forename: S
authors.initials: S
authors.lastname: Tammaro
authors.affiliation: 1] AILES Beamline, Synchrotron SOLEIL, l'Orme des Merisiers, Saint-Aubin, Gif-sur-Yvette 91192, France [2] Institut des Sciences Moléculaires d'Orsay, UMR8214 CNRS-Université Paris-Sud, Bâtiment 210, Orsay 91405, France.
authors.forename: O
authors.initials: O
authors.lastname: Pirali
authors.affiliation: AILES Beamline, Synchrotron SOLEIL, l'Orme des Merisiers, Saint-Aubin, Gif-sur-Yvette 91192, France.
authors.forename: P
authors.initials: P
authors.lastname: Roy
authors.affiliation: Institut d'Electronique de Microélectronique et de Nanotechnologie, UMR8520 CNRS-Université de Lille 1, Avenue Poincaré-Cité Scientifique CS 60069, Villeneuve d'Ascq 59652, France.
authors.forename: J-F
authors.initials: JF
authors.lastname: Lampin
authors.affiliation: Institut d'Electronique de Microélectronique et de Nanotechnologie, UMR8520 CNRS-Université de Lille 1, Avenue Poincaré-Cité Scientifique CS 60069, Villeneuve d'Ascq 59652, France.
authors.forename: G
authors.initials: G
authors.lastname: Ducournau
authors.affiliation: Laboratoire de Physico-Chimie de l'Atmosphère, Université du Littoral Côte d'Opale, EA4493 CNRS, 189A Avenue Maurice Schumann, Dunkerque 59140, France.
authors.forename: A
authors.initials: A
authors.lastname: Cuisset
authors.affiliation: Laboratoire de Physico-Chimie de l'Atmosphère, Université du Littoral Côte d'Opale, EA4493 CNRS, 189A Avenue Maurice Schumann, Dunkerque 59140, France.
authors.forename: F
authors.initials: F
authors.lastname: Hindle
authors.affiliation: Laboratoire de Physico-Chimie de l'Atmosphère, Université du Littoral Côte d'Opale, EA4493 CNRS, 189A Avenue Maurice Schumann, Dunkerque 59140, France.
authors.forename: G
authors.initials: G
authors.lastname: Mouret