Skip to Main Content
A new standard is currently being developed in the 30 THz region, using SF6 two-photon Ramsey fringes as a reference. A standard in this region is important for several reasons: molecular spectroscopy, fundamental measurements on molecular systems such as tests of the violation of parity or the Pauli principle in molecules, and temporal variation of the fundamental constants. A new system has implemented consisting of a femtosecond laser system for frequency measurement which allows direct measurement and control of the absolute frequency of the CO2laser. The reference frequency is provided by a 100 MHz signal controlled by the H-maser and the Cs fountain of the BNM-SYRTE in Paris, and transmitted to the laboratory through an optical fibre. The whole system can be used for spectroscopic purposes, here measuring the SF6 transition, with an improved long term stability of the reference laser via the femtosecond system.