title: Nonlinear amplification of side-modes in frequency combs.
abstract: We investigate how suppressed modes in frequency combs are modified upon frequency doubling and self-phase modulation. We find, both experimentally and by using a simplified model, that these side-modes are amplified relative to the principal comb modes. Whereas frequency doubling increases their relative strength by 6 dB, the growth due to self-phase modulation can be much stronger and generally increases with nonlinear propagation length. Upper limits for this effect are derived in this work. This behavior has implications for high-precision calibration of spectrographs with frequency combs used for example in astronomy. For this application, Fabry-Pérot filter cavities are used to increase the mode spacing to exceed the resolution of the spectrograph. Frequency conversion and/or spectral broadening after non-perfect filtering reamplify the suppressed modes, which can lead to calibration errors.
authors.affiliation: Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str 1, 85748 Garching, Germany. rprobst@mpq.mpg.de
authors.forename: R A
authors.initials: RA
authors.lastname: Probst
authors.forename: T
authors.initials: T
authors.lastname: Steinmetz
authors.forename: T
authors.initials: T
authors.lastname: Wilken
authors.forename: H
authors.initials: H
authors.lastname: Hundertmark
authors.forename: S P
authors.initials: SP
authors.lastname: Stark
authors.forename: G K L
authors.initials: GK
authors.lastname: Wong
authors.forename: P St J
authors.initials: PS
authors.lastname: Russell
authors.forename: T W
authors.initials: TW
authors.lastname: Hänsch
authors.forename: R
authors.initials: R
authors.lastname: Holzwarth
authors.forename: Th
authors.initials: T
authors.lastname: Udem
mesh_terms: D000669:Amplifiers, Electronic; D003198:Computer Simulation; D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007368:Interferometry / Q000295:instrumentation*; D008962:Models, Theoretical; D017711:Nonlinear Dynamics; D012031:Refractometry / Q000295:instrumentation*; D013057:Spectrum Analysis / Q000295:instrumentation*