title: Multicolor cavity metrology.
abstract: Long-baseline laser interferometers used for gravitational-wave detection have proven to be very complicated to control. In order to have sufficient sensitivity to astrophysical gravitational waves, a set of multiple coupled optical cavities comprising the interferometer must be brought into resonance with the laser field. A set of multi-input, multi-output servos then lock these cavities into place via feedback control. This procedure, known as lock acquisition, has proven to be a vexing problem and has reduced greatly the reliability and duty factor of the past generation of laser interferometers. In this article, we describe a technique for bringing the interferometer from an uncontrolled state into resonance by using harmonically related external fields to provide a deterministic hierarchical control. This technique reduces the effect of the external seismic disturbances by 4 orders of magnitude and promises to greatly enhance the stability and reliability of the current generation of gravitational-wave detectors. The possibility for using multicolor techniques to overcome current quantum and thermal noise limits is also discussed.
authors.affiliation: Department of Astronomy, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo, Japan.
authors.forename: Kiwamu
authors.initials: K
authors.lastname: Izumi
authors.forename: Koji
authors.initials: K
authors.lastname: Arai
authors.forename: Bryan
authors.initials: B
authors.lastname: Barr
authors.forename: Joseph
authors.initials: J
authors.lastname: Betzwieser
authors.forename: Aidan
authors.initials: A
authors.lastname: Brooks
authors.forename: Katrin
authors.initials: K
authors.lastname: Dahl
authors.forename: Suresh
authors.initials: S
authors.lastname: Doravari
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Driggers
authors.forename: W Zach
authors.initials: WZ
authors.lastname: Korth
authors.forename: Haixing
authors.initials: H
authors.lastname: Miao
authors.forename: Jameson
authors.initials: J
authors.lastname: Rollins
authors.forename: Stephen
authors.initials: S
authors.lastname: Vass
authors.forename: David
authors.initials: D
authors.lastname: Yeaton-Massey
authors.forename: Rana X
authors.initials: RX
authors.lastname: Adhikari