title: Optical frequency synthesis from a cryogenic microwave sapphire oscillator.
abstract: We demonstrate an optical frequency comb with fractional frequency instability of </=2x10(-14) at measurement times near 1 s, when the 10th harmonic of the comb spacing is controlled by a liquid helium cooled microwave sapphire oscillator. The frequency instability of the comb is estimated by comparing it to a cavity-stabilized optical oscillator. The less conventional approach of synthesizing low-noise optical signals from a microwave source is relevant when a laboratory has microwave sources with frequency stability superior to their optical counterparts. We describe the influence of high frequency environmental noise and how it impacts the phase-stabilized frequency comb performance at integration times less than 1 s.
authors.forename: J J
authors.initials: JJ
authors.lastname: McFerran
authors.forename: S T
authors.initials: ST
authors.lastname: Dawkins
authors.forename: P L
authors.initials: PL
authors.lastname: Stanwix
authors.forename: M E
authors.initials: ME
authors.lastname: Tobar
authors.forename: A N
authors.initials: AN
authors.lastname: Luiten