Frequency noise performances of a Ti:sapphire optical frequency comb stabilized to an optical reference

We report on a detailed analysis of frequency noise and intensity dynamics of a free-running femtosecond Ti:sapphire optical frequency comb (OFC) pumped by a multi-mode 532 nm laser. We have used these results for phase locking the OFC to a Hz-wide, cavity stabilized, 698 nm semiconductor laser. An analysis of the in-loop error signals and an estimation of Allan deviation indicates a lower limit for the frequency stability of the OFC at the level of ∼5.3×10−14∼5.3×10−14 for 125 ms integration time comparable with the clock laser frequency stability over the entire OFC spectrum. The noise transfer processes between the pump laser and the Ti:sapphire laser have been studied in detail, comparing the resulting frequency noise of the OFC output spectrum with both a single-mode and a multi-mode pump lasers. In the latter case, we employed a pump beam steering control to maintain an OFC regime with a minimum impact of pump laser amplitude noise on the carrier-envelope offset frequency.