Diffraction Error in Laser Interferometry for the Measurement of the 28Si Lattice Parameter

This paper describes how the angular spectrum of a laser beam is determined, in order to estimate the relevant correction in optical interferometers as applied to length measurements. Tests and numerical simulations carried out to assess the measurement procedure delivered clues of deviations from a free-space propagation due to scattering centers in the beam path. Based on the simulation results, additional measurements are ongoing to confirm this evidence.