Nonlinear phase accumulation for a linear path delay in low coherence fourier transform spectral interferometry

Abstract

Abstract A scheme to measure path delay in spectral interferometry by observing the phase accumulated by the superposed field is presented. Through the interference with an additional reference beam maintained at an out-of-phase condition near zero optical path delay with respect to the sample probe beam, a nonlinearity in measured phase is observed. A detailed simulation is presented, and its experimental proof-of concept demonstration is attempted using the classic low coherence spectral interferometry. The spectral phase is measured from the modulations in the recorded spectral interference using Fourier transform method of fringe analysis. A systematic calibration for setting up the experiment even with unknown parameters like amplitude ratio among the interfering fields, and location of the zero optical path delay is also provided.