Balanced homodyne detection is typically used to measure quantum-noise-limited optical beams, including squeezed states of light, at audio-band frequencies. Current designs of advanced gravitational ...wave interferometers use some type of homodyne readout for signal detection, in part because of its compatibility with the use of squeezed light. The readout scheme used in Advanced LIGO, called DC readout, is however not a balanced detection scheme. Instead, the local oscillator field, generated from a dark fringe offset, co-propagates with the signal field at the anti-symmetric output of the beam splitter. This article examines the alternative of a true balanced homodyne detection for the readout of gravitational wave detectors such as Advanced LIGO. Several practical advantages of the balanced detection scheme are described.
Second generation gravitational wave detectors are being installed in a number of locations globally. These long-baseline, Michelson interferometers increase the sensitivity between 10 and 40 Hz by ...many orders of magnitude compared with first generation instruments. Control of non-linear noise coupling from scattered light fields is critical to achieve low frequency performance. In this paper we investigate the requirements on the attenuation of scattered light using a novel time-domain analysis and two years of seismic data from the LIGO Livingston Observatory.
It has been suggested that the next generation of interferometric gravitational wave detectors may observe spontaneously excited parametric oscillatory instabilities. We present a method of actively ...suppressing any such instability through application of electrostatic forces to the interferometers' test masses. Using numerical methods we quantify the actuation force required to damp candidate instabilities and find that such forces are readily achievable. Our predictions are subsequently verified experimentally using prototype Advanced LIGO hardware, conclusively demonstrating the effectiveness of our approach.
The advanced LIGO gravitational wave detectors need high power laser sources with excellent beam quality and low-noise behavior. We present a pre-stabilized laser system with 70 W of output power ...that was used in the third observing run of the advanced LIGO detectors. Furthermore, the prototype of a 140 W pre-stabilized laser system for future use in the LIGO observatories is described and characterized.
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