title: Coherence properties of a 2.6-7.5  μm frequency comb produced as a subharmonic of a Tm-fiber laser.
abstract: We study the temporal coherence of an ultrabroadband frequency comb produced in a degenerate GaAs optical parametric oscillator (OPO) pumped by a stabilized Tm-fiber comb, by observing multiheterodyne beats in the RF domain. We infer that in such a regime the OPO automatically produces a stable frequency comb that is phase and frequency locked to the pump. By varying intracavity dispersion, we achieve a comb spanning 2.6-7.5 μm at a -20  dB level. Low pump threshold (down to 7 mW), high average power (up to 73 mW), broad spectral coverage, flat spectrum, and high coherence make this comb a source suitable for various applications, foremost dual-comb molecular spectroscopy.
authors.forename: V O
authors.initials: VO
authors.lastname: Smolski
authors.forename: H
authors.initials: H
authors.lastname: Yang
authors.forename: S D
authors.initials: SD
authors.lastname: Gorelov
authors.forename: P G
authors.initials: PG
authors.lastname: Schunemann
authors.forename: K L
authors.initials: KL
authors.lastname: Vodopyanov