Enhancing the Bandwidth of Gravitational-Wave Detectors with Unstable Optomechanical Filters
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.
© 2015 American Physical Society. Received 18 June 2015; revised manuscript received 29 September 2015; published 17 November 2015. We thank H. Yang, M. Wang, and other members of the LIGO-MQM discussion group for fruitful discussions. H. M. is supported by a Marie-Curie Fellowship. Y. C. is supported by NSF Grant No. PHY-1068881 and NSF CAREER Grant No. PHY-0956189. Y.M. and C. Z. have been supported by the Australian Research Council.
Submitted - 1506.00117v1.pdf
Published - PhysRevLett.115.211104.pdf