Absolute frequency measurement in the 28 THz spectral region with a femtosecond laser comb and a long-distance optical link to a primary standard

Anne Amy-Klein (1) , Andrei Goncharov (1) , Christophe Daussy (1) , Christophe Grain (1) , Olivier Lopez (1) , Georgio Santarelli (2) , Christian Chardonnet (1)

1 LPL - Laboratoire de Physique des Lasers
2 SYRTE - Systèmes de Référence Temps Espace

A new frequency chain was demonstrated to measure an optical frequency standard based on a rovibrational molecular transition in the 28 THz spectral region accessible to a CO2 laser. It uses a femtosecond-laser frequency comb generator and two laser diodes at 852 nm and 788 nm as intermediate oscillators, with their frequency difference phase-locked to the CO2 laser. The RF repetition rate of the femtosecond laser was compared with a 100-MHz signal from a Hydrogen Maser, located at BNM-SYRTE. The 100 MHz signal is transmitted by amplitude modulation of a 1.55 µm laser diode through a 43-km telecommunication optical fibre. As a first example, the absolute measurement of a saturation line of OsO4 in the vicinity of the P(16) laser line of CO2 is reported with a relative uncertainty of 10-12, limited by the CO2/OsO4 frequency day-to-day reproducibility. The current limit on the stability of the frequency measurement is 4´10-13 at 1 s.

Mots clés: métrologie; physique moléculaire; lien optique

Domaines: Physique Quantique [quant-ph]

Anne Amy-Klein, Andrei Goncharov, Christophe Daussy, Christophe Grain, Olivier Lopez, et al.. Absolute frequency measurement in the 28 THz spectral region with a femtosecond laser comb and a long-distance optical link to a primary standard. Applied Physics B - Laser and Optics, 2004, 78, pp.25-30. ⟨hal-00003119⟩