title: Millimeter-long fiber Fabry-Perot cavities.
abstract: We demonstrate fiber Fabry-Perot (FFP) cavities with concave mirrors that can be operated at cavity lengths as large as 1.5 mm without significant deterioration of the finesse. This is achieved by using a laser dot machining technique to shape spherical mirrors with ultralow roughness and employing single-mode fibers with large mode area for good mode matching to the cavity. Additionally, in contrast to previous FFPs, these cavities can be used over an octave-spanning frequency range with adequate coatings. We also show directly that shape deviations caused by the fiber's index profile lead to a finesse decrease as observed in earlier attempts to build long FFP cavities, and show a way to overcome this problem.
authors.forename: Konstantin
authors.initials: K
authors.lastname: Ott
authors.forename: Sebastien
authors.initials: S
authors.lastname: Garcia
authors.forename: Ralf
authors.initials: R
authors.lastname: Kohlhaas
authors.forename: Klemens
authors.initials: K
authors.lastname: Schüppert
authors.forename: Peter
authors.initials: P
authors.lastname: Rosenbusch
authors.forename: Romain
authors.initials: R
authors.lastname: Long
authors.forename: Jakob
authors.initials: J
authors.lastname: Reichel