title: Characterization of a DFG comb showing quadratic scaling of the phase noise with frequency.
abstract: We characterize an Er:fiber laser frequency comb that is passively carrier envelope phase-stabilized via difference frequency generation at a wavelength of 1550 nm. A generic method to measure the comb linewidth at different wavelengths is demonstrated. By transferring the properties of a comb line to a cw external cavity diode laser, the phase noise is subsequently measured by tracking the delayed self-heterodyne beat note. This relatively simple characterization method is suitable for a broad range of optical frequencies. Here, it is used to characterize our difference frequency generation (DFG) comb over nearly an optical octave. With repetition-rate stabilization, a radiofrequency reference oscillator limited linewidth is achieved. A lock to an optical reference shows out-of-loop linewidths of the comb at the hertz level. The phase noise measurements are in excellent agreement with the elastic tape model with a fix point at zero frequency.
authors.forename: Thomas
authors.initials: T
authors.lastname: Puppe
authors.forename: Alexander
authors.initials: A
authors.lastname: Sell
authors.forename: Russell
authors.initials: R
authors.lastname: Kliese
authors.forename: Nazanin
authors.initials: N
authors.lastname: Hoghooghi
authors.forename: Armin
authors.initials: A
authors.lastname: Zach
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Kaenders