Computational approach to phase detection in frequency-modulation interferometry

We present a new approach to the interference phase detection in the frequency-modulation interferometry. Using a frequency-tunable laser beam and several computational steps we show that the interference phase can be detected with a sub-nanometer resolution from a single interference signal coming from a non-polarizing interferometer sampled by a single photo-detector. This represents significant simplification of the necessary optical setup in comparison to the conventional homodyne interferometry that requires several polarizing optical elements to produce two interference signals in quadrature. The experimental results show that our method achieves comparable accuracy as the homodyne detection which makes it usable in applications where the interferometric setup simplicity is necessary.