Improving the accuracy of homodyne Michelson interferometers using polarisation state measurement techniques

We demonstrate a simple homodyne Michelson interferometer design capable of fringe interpolation accuracy of one part in 36,000 leading to a potential accuracy of 10 pm. This improvement becomes possible thanks to the significant advances in polarimetry that permit measurement of the ellipsometric parameters ψ and Δ with an accuracy of 0.01° with readily available commercial equipment. The proposed method has been set up and we make a direct comparison with a commercial heterodyne interferometer by measuring the displacement of the same target mirror. This latter has been displaced by steps of 20 nm using a high accuracy position control method.