title: Frequency comb metrology with an optical parametric oscillator.
abstract: We report on the first demonstration of absolute frequency comb metrology with an optical parametric oscillator (OPO) frequency comb. The synchronously-pumped OPO operated in the 1.5-µm spectral region and was referenced to an H-maser atomic clock. Using different techniques, we thoroughly characterized the frequency noise power spectral density (PSD) of the repetition rate frep, of the carrier-envelope offset frequency fCEO, and of an optical comb line νN. The comb mode optical linewidth at 1557 nm was determined to be ~70 kHz for an observation time of 1 s from the measured frequency noise PSD, and was limited by the stability of the microwave frequency standard available for the stabilization of the comb repetition rate. We achieved a tight lock of the carrier envelope offset frequency with only ~300 mrad residual integrated phase noise, which makes its contribution to the optical linewidth negligible. The OPO comb was used to measure the absolute optical frequency of a near-infrared laser whose second-harmonic component was locked to the F = 2→3 transition of the87Rb D2 line at 780 nm, leading to a measured transition frequency of νRb= 384,228,115,346 ± 16 kHz. We performed the same measurement with a commercial fiber-laser comb operating in the 1.5-µm region. Both the OPO comb and the commercial fiber comb achieved similar performance. The measurement accuracy was limited by interferometric noise in the fibered setup of the Rb-stabilized laser.
authors.forename: K
authors.initials: K
authors.lastname: Balskus
authors.forename: S
authors.initials: S
authors.lastname: Schilt
authors.forename: V J
authors.initials: VJ
authors.lastname: Wittwer
authors.forename: P
authors.initials: P
authors.lastname: Brochard
authors.forename: T
authors.initials: T
authors.lastname: Ploetzing
authors.forename: N
authors.initials: N
authors.lastname: Jornod
authors.forename: R A
authors.initials: RA
authors.lastname: McCracken
authors.forename: Z
authors.initials: Z
authors.lastname: Zhang
authors.forename: A
authors.initials: A
authors.lastname: Bartels
authors.forename: D T
authors.initials: DT
authors.lastname: Reid
authors.forename: T
authors.initials: T
authors.lastname: Südmeyer