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.
View Article and Find Full Text PDF