Experimental demonstration of resonant sideband extraction in a sagnac interferometer

Sagnac interferometers have recently been proposed as a potential alternative to Michelson interferometers for the purpose of large-scale laser interferometric gravitational-wave detectors. We report on an experimental investigation of the Sagnac interferometer in two configurations: with arm cavities, and with resonant sideband extraction. Resonant sideband extraction was shown to increase the signal bandwidth by a factor of 6.5 compared with the arm cavity device, corresponding to an increase in sensitivity of as much as 6 dB for signals outside the arm cavity bandwidth. Moreover, we compare the performance of a Sagnac interferometer with resonant sideband extraction to a Michelson interferometer with resonant sideband extraction.