Testing ultrafast mode-locking at microhertz relative optical linewidth
Martin, Michael J.
Foreman, Seth M.
Schibli, T. R.
Physics - Optics
arxiv: Physics::Optics | Physics::Atomic Physics
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 micro Hz 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.