title: Interferometric wavefront sensing with a single diode using spatial light modulation.
abstract: We present a new technique for the fine alignment sensing of optical interferometers. Unlike conventional wavefront sensing systems, which use multielement photodiodes, this approach works with a single-element photodiode, in combination with a spatial light modulator (SLM) and digitally enhanced heterodyne interferometry. As all signals pass through a single photodetection and analog path, the technique exhibits high common-mode rejection to low frequency errors present in conventional systems. By changing the modulation pattern on the SLM, the technique can also be extended to sensing higher-order wavefront errors. In this paper, we demonstrate the technique experimentally and compare performance with a conventional heterodyne wavefront sensing system. This may improve and simplify alignment systems in space-based interferometers such as the planned LISA gravitational wave detector and provide a way to optimize the power in laser cavities not possible with the traditional segmented diode approach.
authors.forename: D
authors.initials: D
authors.lastname: Tarquin Ralph
authors.forename: Paul A
authors.initials: PA
authors.lastname: Altin
authors.forename: David S
authors.initials: DS
authors.lastname: Rabeling
authors.forename: David E
authors.initials: DE
authors.lastname: McClelland
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Shaddock