title: Testing ultrafast mode-locking at microhertz relative optical linewidth.
abstract: We report new limits on the phase coherence of the ultrafast mode-locking process in an octave-spanning Ti:sapphire comb.We find that the mode-locking mechanism correlates optical phase across a full optical octave with less than 2.5 microHZ relative linewidth. This result is at least two orders of magnitude below recent predictions for quantum-limited individual comb-mode linewidths, verifying that the mode-locking mechanism strongly correlates quantum noise across the comb spectrum.
authors.affiliation: JILA, National Institute of Standards and Technology and University of Colorado Department of Physics, University of Colorado, Boulder, CO 80309-0440, USA. Michael.J.Martin@colorado.edu
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Martin
authors.forename: Seth M
authors.initials: SM
authors.lastname: Foreman
authors.forename: T R
authors.initials: TR
authors.lastname: Schibli
authors.forename: Jun
authors.initials: J
authors.lastname: Ye