title: A multi-branch, fiber-based frequency comb with millihertz-level relative linewidths using an intra-cavity electro-optic modulator.
abstract: We demonstrate that fiber-based frequency combs with multi-branch configurations can transfer both linewidth and frequency stability to another wavelength at the millihertz level. An intra-cavity electro-optic modulator is employed to obtain a broad servo bandwidth for repetition rate control. We investigate the relative linewidths between two combs using a stable continuous-wave laser as a common reference to stabilize the repetition rate frequencies in both combs. The achieved energy concentration to the carrier of the out-of-loop beat between the two combs was 99% and 30% at a bandwidth of 1 kHz and 7.6 mHz, respectively. The frequency instability of the comb was 3.7x10(-16) for a 1 s averaging time, improving to 5-8x10(-19) for 10000 s. We show that the frequency noise in the out-of-loop beat originates mainly from phase noise in branched optical fibers.
authors.affiliation: University of Fukui, Fukui, Fukui-ken, Japan.
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Nakajima
authors.forename: Hajime
authors.initials: H
authors.lastname: Inaba
authors.forename: Kazumoto
authors.initials: K
authors.lastname: Hosaka
authors.forename: Kaoru
authors.initials: K
authors.lastname: Minoshima
authors.forename: Atsushi
authors.initials: A
authors.lastname: Onae
authors.forename: Masami
authors.initials: M
authors.lastname: Yasuda
authors.forename: Takuya
authors.initials: T
authors.lastname: Kohno
authors.forename: Sakae
authors.initials: S
authors.lastname: Kawato
authors.forename: Takao
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Toshio
authors.initials: T
authors.lastname: Katsuyama
authors.forename: Feng-Lei
authors.initials: FL
authors.lastname: Hong
mesh_terms: D004581:Electronics / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005336:Fiber Optic Technology / Q000295:instrumentation*; D005374:Filtration / Q000295:instrumentation*; D007834:Lasers; D008872:Microwaves; D055096:Optical Devices; D012031:Refractometry / Q000295:instrumentation*; D014159:Transducers