Use of range-resolved interferometry for single-beam differential velocity measurements in a photon momentum setup

Abstract This work showcases the novel possibilities that the use of range-resolved interferometry (RRI) can provide to high-precision force measurement systems based on the Kibble principle. The RRI technique, using sinusoidal laser frequency modulation of diode lasers, enables the simultaneous readout of multiple interferometric phase signals that differ in their optical path differences, enabling the direct measurement of differential motion signals along a single optical beam. The conceptual optical and mechanical system design along with the methodology for data synchronization for the velocity mode measurements in a table-top photon momentum setup is described. Velocity measurements of oscillatory motions with frequencies between 0.1 Hz and 150 Hz and with deflections amplitudes of up to 50 µm are obtained at sub-nm resolution. Metrologically well-characterized cuboid-shaped glass blocks are used as partial reflectors along the measurement axis to obtain multiple interference signals. This optical configuration, which uses only a single straight measuring beam can significantly minimize errors due to angular misalignment and tilt and therefore shows a new route to ultimately lower geometric uncertainties in Kibble-based setups.