title: Measurement of the spectrally-resolved absolute phase difference between orthogonal optical modes using a nonlinear beat signal.
abstract: On the basis of white-light interferometry with spectrally integrated detection and Fourier transform (FT) analysis, we demonstrate a novel technique for measuring the spectrally-resolved absolute phase difference between orthogonal optical modes with milliradian precision. The phase difference is evaluated from a nonlinear beat signal, occurring in the phase spectrum when independent interferograms, formed by individual modes, are recorded simultaneously. Although scanning white-light FT interferometry is a linear technique in general, the nonlinear beat signal is due to spectral amplitude variations in each mode. These proof-of-principle absolute phase difference measurements were carried out with polarization and spatial fiber modes.
authors.forename: Anastassia
authors.initials: A
authors.lastname: Gosteva
authors.forename: Markus
authors.initials: M
authors.lastname: Haiml
authors.forename: Ursula
authors.initials: U
authors.lastname: Keller