Correction of nonlinearity in one-frequency optical interferometry

The nonlinearity of one-frequency optical interferometry with quadrature fringe detection is the result of a number of factors including polarization mixing, unequal gain of detectors, imbalanced beams and lack of quadrature. An elliptical least-squares fitting technique to correct the nonlinearity is presented in this paper. Experimental results demonstrate that a nonlinearity-free condition can be achieved and the stability of the interferometer set-up in our laboratory is better than +/-0.7 nm over 2.5 h.