Evaluation of Refractive Index from Interference-Fringe Transmission Spectra

Abstract

The refractive index of dielectric or semiconducting media is often calculated from interference-fringe transmission spectra in the wavelength range of interest. An analysis shows the fundamental relationships involved. Because the basis for the procedures used in the calculation is sometimes not fully realized, the discussion indicates the typical incorrect application of the method, and (1) presents explicitly the proper analysis and its interpretation, (2) derives expressions for evaluating all the coefficients except that of the linear term in the usual relationship for the refractive index as a power series in the wavelength, (3) describes a diagnostic test for the significant occurrence of terms in the series other than the constant and the linear term, and (4) discusses a defect in the method and a possible way to overcome it.