Progress in optical frequency measurements at BNM-SYRTE

Abstract

We report recent progress in optical frequency measurements at the BNM-SYRTE. The work presented is centered around the development of a frequency measurement chain based on a femtosecond laser (Diddams, 2001) and the construction of an optical frequency standard (OFS) using cold Sr atoms. The Kerr lens mode-locked femtosecond laser is centered at 800 nm with a repetition rate at 840 MHz, locked to a cryogenic oscillator referenced to a primary Cs standard. The frequency comb from the laser is broadened to more than an optical octave in a photonic crystal fiber. The infrared part of the frequency comb is frequency doubled in KTP and heterodyned with the green part of the spectrum to yield the carrier envelope offset frequency. For absolute frequency measurements, the CW laser from an OFS is superimposed with the frequency comb, and the beat signal with an adjacent line is measured. We present recent developments in our setup, as well as recent experiments on high stability transfer between various OFS in the lab