Achieving resonance in the Advanced LIGO gravitational-wave interferometer

A. Staley, Denis Martynov

Research output: Contribution to journalArticlepeer-review

41 Citations (Scopus)


Interferometric gravitational-wave detectors are complex instruments comprised of a Michelson interferometer enhanced by multiple coupled cavities. Active feedback control is required to operate these instruments and keep the cavities locked on resonance. The optical response is highly nonlinear until a good operating point is reached. The linear operating range is between 0.01% and 1% of a fringe for each degree of freedom. The resonance lock has to be achieved in all five degrees of freedom simultaneously, making the acquisition difficult. Furthermore, the cavity linewidth seen by the laser is only ~1 Hz, which is four orders of magnitude smaller than the linewidth of the free running laser. The arm length stabilization system is a new technique used for arm cavity locking in Advanced LIGO. Together with a modulation technique utilizing third harmonics to lock the central Michelson interferometer, the Advanced LIGO detector has been successfully locked and brought to an operating point where detecting gravitational-waves becomes feasible.
Original languageEnglish
Article number245010
Number of pages14
JournalClassical and Quantum Gravity
Issue number24
Publication statusPublished - 26 Nov 2014


  • LIGO
  • gravitational-wave detector
  • interferometer


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