title: Phase noise characterization of sub-hertz linewidth lasers via digital cross correlation.
abstract: Phase noise or frequency noise is a key metric to evaluate the short-term stability of a laser. This property is of great interest for the applications but delicate to characterize, especially for narrow linewidth lasers. In this Letter, we demonstrate a digital cross-correlation scheme to characterize the absolute phase noise of sub-hertz linewidth lasers. Three 1542 nm ultra-stable lasers are used in this approach. For each measurement, two lasers act as references to characterize a third one. Phase noise power spectral density from 0.5 Hz to 0.8 MHz Fourier frequencies can be derived for each laser by a mere change in the configuration of the lasers. To the best of our knowledge, this is the first time showing the phase noise of sub-hertz linewidth lasers with no reference limitation. We also present an analysis of the laser phase noise performance.
authors.forename: Xiaopeng
authors.initials: X
authors.lastname: Xie
authors.forename: Romain
authors.initials: R
authors.lastname: Bouchand
authors.forename: Daniele
authors.initials: D
authors.lastname: Nicolodi
authors.forename: Michel
authors.initials: M
authors.lastname: Lours
authors.forename: Christophe
authors.initials: C
authors.lastname: Alexandre
authors.forename: Yann
authors.initials: Y
authors.lastname: Le Coq