title: Optical modulation techniques for length sensing and control of optical cavities.
abstract: We present a discussion of the use of amplitude modulation techniques with regard to the length sensing and control of optical cavities for laser interferometric gravitational-wave detectors. Traditional radio-frequency amplitude modulation techniques automatically include phase modulation as a product of the modulation process, which can contaminate the signal after demodulation. In particular, with many length-sensing and control schemes the detected signals are demodulated in quadrature, which, in the case of a traditional amplitude modulation scheme, will result in offsets due to the additional phase modulation. We demonstrate this effect using a simple optical cavity configuration and show that minor adjustments to the modulator system can be used to compensate for the extra modulation components and provide additional flexibility.
authors.affiliation: Department of Physics and Astronomy, University of Glasgow, University Avenue, Glasgow G12 8QQ, Scotland. b.barr@physics.gla.ac.uk
authors.forename: B W
authors.initials: BW
authors.lastname: Barr
authors.forename: S H
authors.initials: SH
authors.lastname: Huttner
authors.forename: J R
authors.initials: JR
authors.lastname: Taylor
authors.forename: B
authors.initials: B
authors.lastname: Sorazu
authors.forename: M V
authors.initials: MV
authors.lastname: Plissi
authors.forename: K A
authors.initials: KA
authors.lastname: Strain