Phase-amplitude noise correlations in an optical frequency comb

The use of optical frequency combs (FC) for high precision measurements is limited by fluctuations of the comb structure [1]. The FC fluctuations can be modelled as uncoupled noise modes associated with a few global parameters namely power, central wavelength, carrier-envelope offset (CEO) phase, repetition rate, dispersion [2, 3]. However, the correlations between phase and amplitude noises, which play an important role to determine the comb stability, have never been described in terms of these noise modes. In this study, we present a new scheme to measure both phase and amplitude noises simultaneously, and provide a modal description of their correlations to unveil the underlying physical mechanisms.