title: Experimental demonstration of deep frequency modulation interferometry.
abstract: Experiments for space and ground-based gravitational wave detectors often require a large dynamic range interferometric position readout of test masses with 1 pm/√Hz precision over long time scales. Heterodyne interferometer schemes that achieve such precisions are available, but they require complex optical set-ups, limiting their scalability for multiple channels. This article presents the first experimental results on deep frequency modulation interferometry, a new technique that combines sinusoidal laser frequency modulation in unequal arm length interferometers with a non-linear fit algorithm. We have tested the technique in a Michelson and a Mach-Zehnder Interferometer topology, respectively, demonstrated continuous phase tracking of a moving mirror and achieved a performance equivalent to a displacement sensitivity of 250 pm/Hz at 1 mHz between the phase measurements of two photodetectors monitoring the same optical signal. By performing time series fitting of the extracted interference signals, we measured that the linearity of the laser frequency modulation is on the order of 2% for the laser source used.
authors.forename: Katharina-Sophie
authors.initials: KS
authors.lastname: Isleif
authors.forename: Oliver
authors.initials: O
authors.lastname: Gerberding
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Schwarze
authors.forename: Moritz
authors.initials: M
authors.lastname: Mehmet
authors.forename: Gerhard
authors.initials: G
authors.lastname: Heinzel
authors.forename: Felipe Guzmán
authors.initials: FG
authors.lastname: Cervantes