Abstract

Interferometric gravitational-wave detectors, such as the Laser Interferometer Gravitational Wave Observatory (LIGO) detectors currently under construction, are based on kilometer-scale Michelson interferometers, with sensitivity that is enhanced by addition of multiple coupled optical resonators. Reducing the relative optic motions to bring the system to the resonant operating point is a significant challenge. We present a new approach to lock acquisition, used to lock a LIGO interferometer, whereby the sensor transformation matrix is dynamically calculated to sequentially bring the cavities into resonance.

© 2002 Optical Society of America

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References

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  1. B. C. Barish and R. Weiss, Phys. Today 52(10), 44 (1999).
    [CrossRef]
  2. M. W. Regehr, F. J. Raab, and S. E. Whitcomb, Opt. Lett. 20, 1507 (1995).
    [CrossRef] [PubMed]
  3. P. Fritschel, R. Bork, G. González, N. Mavalvala, D. Ouimette, H. Rong, D. Sigg, and M. Zucker, Appl. Opt. 40, 4988 (2001).
    [CrossRef]
  4. J. Camp, L. Sievers, R. Bork, and J. Heefner, Opt. Lett. 20, 2463 (1995).
    [CrossRef]
  5. M. Evans, “Lock acquisition in resonant optical interferometers,” Ph.D. dissertation (California Institute of Technology, Pasadena, Calif., 2001).

2001

1999

B. C. Barish and R. Weiss, Phys. Today 52(10), 44 (1999).
[CrossRef]

1995

Barish, B. C.

B. C. Barish and R. Weiss, Phys. Today 52(10), 44 (1999).
[CrossRef]

Bork, R.

Camp, J.

Evans, M.

M. Evans, “Lock acquisition in resonant optical interferometers,” Ph.D. dissertation (California Institute of Technology, Pasadena, Calif., 2001).

Fritschel, P.

González, G.

Heefner, J.

Mavalvala, N.

Ouimette, D.

Raab, F. J.

Regehr, M. W.

Rong, H.

Sievers, L.

Sigg, D.

Weiss, R.

B. C. Barish and R. Weiss, Phys. Today 52(10), 44 (1999).
[CrossRef]

Whitcomb, S. E.

Zucker, M.

Appl. Opt.

Opt. Lett.

Phys. Today

B. C. Barish and R. Weiss, Phys. Today 52(10), 44 (1999).
[CrossRef]

Other

M. Evans, “Lock acquisition in resonant optical interferometers,” Ph.D. dissertation (California Institute of Technology, Pasadena, Calif., 2001).

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Figures (3)

Fig. 1
Fig. 1

Power-recycled interferometer with the detection ports shown. In practice, the REC comes from the antireflection-coated surface of the beam splitter, and REF is separated from the input beam with a Faraday isolator. Signals at modulation frequency fm are measured at the REF, REC, and AS by use of in- and quadrature-phase demodulation to generate length error signals (e.g., Iref and Qref); the signal at 2fm is measured at the REC.

Fig. 2
Fig. 2

At each clock sample, five tests (typical values indicated) determine which DOF are controlled from which sensor signals (Mi are defined in the text). Starting from the uncontrolled interferometer, the approach of state 2 is indicated when the 2fm signal crosses 30% of its maximum; the signal’s sign distinguishes the desired rf sideband resonance from a carrier resonance. State 3 is approached when either arm nears a carrier resonance, indicated when its transmission Pi crosses a fraction of the state 3 level. State 4 is entered when both Pi cross a threshold, triggering calculation of M3 and activating the L- control signal. When the normalized determinant of M3 falls below a threshold, the L+,l+ error signal separation becomes poor, and the l+ signal is turned off until the determinant again exceeds threshold. Finally, the l- signal is switched from Qref to Qrec when both Pi exceed 10× the state 3 level, since Qrec becomes more robust—the reflected signal scales with the reflected carrier field, which becomes small and possibly goes through zero.

Fig. 3
Fig. 3

Top, acquisition states of the interferometer. The rf sidebands (blue) resonate in the power-recycling cavity only, whereas the carrier (red) resonates everywhere. Middle, power levels during acquisition (log10 vertical scale), normalized to the input sideband power (blue curve) and to the resonant arm power if there were no recycling mirror (green and red curves); shaded bars indicate the corresponding states. Bottom, L+ and l+ control signal and the normalized determinant of M3 during the state 34 transition (central 0.1 s of upper plot); the determinant goes through zero, and the l+ control signal is tuned off for 15 ms.

Tables (1)

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Table 1 Elements of the Optical Gain Matrix, Ga

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