title: Coherent control of vacuum squeezing in the gravitational-wave detection band.
abstract: We propose and demonstrate a coherent control scheme for stable phase locking of squeezed vacuum fields. We focus on sideband fields at frequencies from 10 Hz to 10 kHz, which is a frequency regime of particular interest in gravitational-wave detection and for which conventional control schemes have failed so far. A vacuum field with broadband squeezing covering this entire band was produced using optical parametric oscillation and characterized with balanced homodyne detection. The system was stably controlled over long periods utilizing two coherent but frequency shifted control fields. In order to demonstrate the performance of our setup the squeezed field was used for a nonclassical sensitivity improvement of a Michelson interferometer at audio frequencies.
authors.affiliation: Max-Planck-Institut für Gravitationsphysik (Albert-Einstein-Institut) and Institut für Gravitationsphysik, Universität Hannover, Callinstrasse 38, 30167 Hannover, Germany.
authors.forename: Henning
authors.initials: H
authors.lastname: Vahlbruch
authors.forename: Simon
authors.initials: S
authors.lastname: Chelkowski
authors.forename: Boris
authors.initials: B
authors.lastname: Hage
authors.forename: Alexander
authors.initials: A
authors.lastname: Franzen
authors.forename: Karsten
authors.initials: K
authors.lastname: Danzmann
authors.forename: Roman
authors.initials: R
authors.lastname: Schnabel