Abstract

The first generation of long-baseline (typically 3km) interferometric gravitational wave detectors should be operational by the end of this decade with relative strain sensitivites expected to be of order 10^-23 for gravity wave frequencies of the order of 10² - 10³ Hz. The overal sensitivity of these instruments is expected to be shot-noise-limited for gravity wave frequencies above several hundred Hz, with thermal and seismic noise dominant at lower frequencies [1,2]. Both the LIGO[l] and VIRGO[2] projects plan to incorporate “optical power recycling” by means of a mirror placed between the laser and beam splitter, forming a resonant optical cavity with the end mirrors. This greatly improves the shot-noise-limited sensitivity by making use of light otherwise rejected from the interferometer to increase the effective input power. Improvements to the shot-noise-limited sensitivity will follow in later generation interferometers with the incorporation of additional optical recycling techniques, such as signal recycling or resonant sideband extraction. Benchtop experiments, trialling proposed configurations on interferometers with arm lengths of the order of 1 metre, will continue to play a vital role in assessing and developing new optical and servo control methods.

© 1996 Optical Society of America