Parallel phase modulation scheme for interferometric gravitational-wave detectors
Advanced LIGO (aLIGO) requires multiple frequency sidebands to disentangle all of the main interferometer's length signals. This paper presents the results of a risk reduction experiment to produce two sets of frequency sidebands in parallel, avoiding mixed 'sidebands on sidebands'. Two phase modulation frequencies are applied to separate Electro-Optic Modulators (EOMs), with one EOM in each of the two arms of a Mach-Zehnder interferometer. In this system the Mach-Zehnder's arm lengths are stabilized to reduce relative intensity noise in the recombined carrier beam by feeding a corrective control signal back to the Rubidium Titanyl Phosphate (RTP) EOM crystals to drive the optical path length difference to zero. This setup's use of the RTP crystals as length actuators provides enough bandwidth in the feedback to meet arm length stability requirements for aLIGO.
© 2014 Optical Society of America. Original Manuscript: August 26, 2014; Revised Manuscript: October 1, 2014; Manuscript Accepted: October 10, 2014; Published: November 6, 2014. This work was supported by NSF grants PHY-0969935 and PHY-1205512. The authors gratefully acknowledge fruitful discussions within the LIGO Scientific Collaboration about this work.
Published - oe-22-23-28327.pdf