Four photon coherent interaction applied to long term stabilization of a femtosecond clock

Summary form only given. The general objective of this work is to provide a stable and accurate frequency standard affordable in any physics laboratory, using the regular frequency comb provided by a mode-locked laser. The frequency of the tooth m of the comb is given by v/sub m/ = v/sub o/ + m/,/spl tau//sub RT/ where /spl tau//sub RT/ is the round-trip time of the pulse in the laser cavity, and v/sub o/ is the zero-offset frequency of the comb. We have previously demonstrated that both the repetition rate and the zero-offset can be stabilized to a fractional instability in less than 800 ms, limited by the clock used for the RF counters used in that measurement.