title: Enhancing the Bandwidth of Gravitational-Wave Detectors with Unstable Optomechanical Filters.
abstract: Advanced interferometric gravitational-wave detectors use optical cavities to resonantly enhance their shot-noise-limited sensitivity. Because of positive dispersion of these cavities-signals at different frequencies pick up different phases, there is a tradeoff between the detector bandwidth and peak sensitivity, which is a universal feature for quantum measurement devices having resonant cavities. We consider embedding an active unstable filter inside the interferometer to compensate the phase, and using feedback control to stabilize the entire system. We show that this scheme in principle can enhance the bandwidth without sacrificing the peak sensitivity. However, the unstable filter under our current consideration is a cavity-assisted optomechanical device operating in the instability regime, and the thermal fluctuation of the mechanical oscillator puts a very stringent requirement on the environmental temperature and the mechanical quality factor.
authors.affiliation: School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, United Kingdom.
authors.forename: Haixing
authors.initials: H
authors.lastname: Miao
authors.affiliation: School of Physics, University of Western Australia, Western Australia 6009, Australia.
authors.forename: Yiqiu
authors.initials: Y
authors.lastname: Ma
authors.affiliation: School of Physics, University of Western Australia, Western Australia 6009, Australia.
authors.forename: Chunnong
authors.initials: C
authors.lastname: Zhao
authors.affiliation: Theoretical Astrophysics 350-17, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: Yanbei
authors.initials: Y
authors.lastname: Chen