title: Enhancement cavities for few-cycle pulses.
abstract: We address the challenge of increasing the bandwidth of high-finesse femtosecond enhancement cavities and demonstrate a broad spectrum spanning 1800  cm-1(195 nm) at -10  dB around a central wavelength of 1050 nm in an EC with an average finesse exceeding 300. This will benefit a host of spectroscopic applications, including transient absorption spectroscopy, direct frequency comb spectroscopy, and Raman spectroscopy. The pulse circulating in the EC is composed of only 5.4 optical cycles, at a kilowatt-level average power. Together with a suitable gating technique, this paves the way to the efficient generation of multi-megahertz-repetition-rate isolated extreme ultraviolet attosecond pulses via intracavity high-order harmonic generation.
authors.forename: N
authors.initials: N
authors.lastname: Lilienfein
authors.forename: C
authors.initials: C
authors.lastname: Hofer
authors.forename: S
authors.initials: S
authors.lastname: Holzberger
authors.forename: C
authors.initials: C
authors.lastname: Matzer
authors.forename: P
authors.initials: P
authors.lastname: Zimmermann
authors.forename: M
authors.initials: M
authors.lastname: Trubetskov
authors.forename: V
authors.initials: V
authors.lastname: Pervak
authors.forename: I
authors.initials: I
authors.lastname: Pupeza