Residual amplitude modulation in interferometric gravitational wave detectors
The effects of residual amplitude modulation (RAM) in laser interferometers using heterodyne sensing can be substantial and difficult to mitigate. In this work, we analyze the effects of RAM on a complex laser interferometer used for gravitational wave detection. The RAM introduces unwanted offsets in the cavity length signals and thereby shifts the operating point of the optical cavities from the nominal point via feedback control. This shift causes variations in the sensing matrix, and leads to degradation in the performance of the precision noise subtraction scheme of the multiple-degree-of-freedom control system. In addition, such detuned optical cavities produce an optomechanical spring, which also perturbs the sensing matrix. We use our simulations to derive requirements on RAM for the Advanced LIGO (aLIGO) detectors, and show that the RAM expected in aLIGO will not limit its sensitivity.
© 2013 Optical Society of America. Received September 19, 2013; revised November 8, 2013; accepted November 10, 2013; posted November 11, 2013 (Doc. ID 197967); published December 10, 2013. We thank the reviewers for their detailed and perceptive commentary. We would like to thank Peter Fritschel and Gabriela Gonzalez for their comments on an early version of the manuscript and our colleagues at the LIGO Livingston Observatory for sharing with us their experiences with RAM over long periods of time. KK was supported by the National Science Foundation with awards 0905184 and 1205882. We also gratefully acknowledge the National Science Foundation for their support under grant PHY-0555406.
Published - josaa-31-1-81.pdf
Submitted - 1309.4522v1.pdf