title: Digitally enhanced homodyne interferometry.
abstract: We present two variations of a novel interferometry technique capable of simultaneously measuring multiple targets with high sensitivity. The technique performs a homodyne phase measurement by application of a four point phase shifting algorithm, with pseudo-random switching between points to allow multiplexed measurement based upon propagation delay alone. By multiplexing measurements and shifting complexity into signal processing, both variants realise significant complexity reductions over comparable methods. The first variant performs a typical coherent detection with a dedicated reference field and achieves a displacement noise floor 0.8 pm/√Hz above 50 Hz. The second allows for removal of the dedicated reference, resulting in further simplifications and improved low frequency performance with a 1 pm/√Hz noise floor measured down to 20 Hz. These results represent the most sensitive measurement performed using this style of interferometry whilst simultaneously reducing the electro-optic footprint.
authors.affiliation: Centre for Gravitational Physics, Department of Quantum Science, The Australian National University, Canberra, ACT 0200, Australia. andrew.sutton@anu.edu.au
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Sutton
authors.forename: Oliver
authors.initials: O
authors.lastname: Gerberding
authors.forename: Gerhard
authors.initials: G
authors.lastname: Heinzel
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Shaddock
mesh_terms: D000465:Algorithms; D000703:Analog-Digital Conversion; D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007368:Interferometry / Q000295:instrumentation* / Q000379:methods*; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*