title: Optical ac coupling to overcome limitations in the detection of optical power fluctuations.
abstract: A high-sensitivity detection method for optical power fluctuations is demonstrated based on photodetection in reflection of an optical resonator with a specific impedance matching. That resonator is used to reduce the carrier power reflected by the resonator while preserving the power fluctuation sidebands for frequencies above the resonator bandwidth. A sensitivity of 7 x 10(-10) Hz(-1/2) for relative power fluctuations was achieved with only 3 mA of detected photocurrent and 99.6% of the power remained for downstream experiments. As in the widely used ac coupling of electrical signals, this technique overcomes dynamic-range limits and reduces detector noise associated with large carrier amplitudes of the optical field.
authors.affiliation: Max-Planck-Institut für Gravitationsphysik (Albert-Einstein-Institut) and Leibniz Universität Hannover, 30167 Hannover, Germany. patrick.kwee@aei.mpg.de
authors.forename: Patrick
authors.initials: P
authors.lastname: Kwee
authors.forename: Benno
authors.initials: B
authors.lastname: Willke
authors.forename: Karsten
authors.initials: K
authors.lastname: Danzmann