Parametric instability in long optical cavities and suppression by dynamic transverse mode frequency modulation

Chunnong Zhao, Li Ju, Qi Fang, Carl Blair, Jiayi Qin, David Blair, Jerome Degallaix, and Hiroaki Yamamoto
Phys. Rev. D 91, 092001 – Published 5 May 2015

Abstract

Three-mode parametric instability has been predicted in advanced gravitational wave detectors. Here we present the first observation of this phenomenon in a large scale suspended optical cavity designed to be comparable to those of advanced gravitational wave detectors. Our results show that previous modeling assumptions that transverse optical modes are stable in frequency except for frequency drifts on a thermal deformation time scale is unlikely to be valid for suspended mass optical cavities. We demonstrate that mirror figure errors cause a dependence of transverse mode offset frequency on spot position. Combined with low-frequency residual motion of suspended mirrors, this leads to transverse mode frequency modulation which suppresses the effective parametric gain. We show that this gain suppression mechanism can be enhanced by laser spot dithering or fast thermal modulation. Using Advanced LIGO test-mass data and thermal modeling, we show that gain suppression factors of 10–20 could be achieved for individual modes, sufficient to greatly ameliorate the parametric instability problem.

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  • Received 18 January 2015

DOI:https://doi.org/10.1103/PhysRevD.91.092001

© 2015 American Physical Society

Authors & Affiliations

Chunnong Zhao, Li Ju, Qi Fang, Carl Blair, Jiayi Qin, and David Blair

  • School of Physics, University of Western Australia, Western Australia 6009, Australia

Jerome Degallaix

  • Laboratoire des Matériaux Avancés, IN2P3/CNRS, Université de Lyon, Villeurbanne 69100, France

Hiroaki Yamamoto

  • Theoretical Physics and Simulation Group, LIGO Caltech, MC 100-36, Pasadena, California 91125, USA

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Vol. 91, Iss. 9 — 1 May 2015

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