The LIGO project is two 4 km baseline interferometers which are currently beingconstructed in the quest to directly detect gravitational radiation. Concurrent withthis effort is research aimed at increasing the strain sensitivity of the initial interferometers to 2.5 x 10^(-23)/√Hz.The optical configuration, which defines the detector gain and bandwidth, is one such area of research. Resonant sideband extraction (RSE) is the configuration which is proposed for advanced LIGO. RSE allows for much more freedom in the optimization of the detector response compared to theinitial configuration.
The principle of RSE is examined in the context of a three mirror coupled cavity.The effect of optical losses on the design of an RSE interferometer is discussed. Twomodel optimizations of the interferometer design are done: one for binary inspiralsources and one for periodic sources at 1 kHz.
An optical heterodyne signal extraction scheme is proposed to sense the deviationof the mirrors away from their nominal positions, and to read out the gravitationalwave signal. The scheme is applied to the two model interferometers previouslydesigned, and its performance is analyzed for each case. Allowable residual deviations of the common mode degrees of freedom are also derived.
A tabletop prototype of an RSE interferometer has been constructed to demonstrateboth the viability of the proposed signal extraction scheme and the tunabilityof the RSE interferometer. Good agreement on both counts is found between themeasured experimental data and the modeled predictions.
The coupling of laser frequency and amplitude noise into the gravitational wavereadout port is analyzed for the RSE configuration assuming the proposed gravitationalwave signal readout scheme. Specifications for the allowable laser frequencyand amplitude noise, as well as allowable residual deviations of the differential modedegrees of freedom, are derived for the two model interferometers.
