Birefringence of muscovite mica

TLDR: In this article, a different procedure is adopted to measure birefringence directly as a single quantity in terms of the thicknesses of mica plates and the wavelengths at which they act as quarterwave or halfwave phase retarders.

Abstract: Birefringence of muscovite mica (ne−no) is usually calculated from the dispersion relations of the indices ne and no. As small differences between relatively large experimentally-measured values, the few available data for birefringence of mica are widely distinct and sometimes contradict basic experimental facts. A different procedure is adopted in this work to measure birefringence directly as a single quantity in terms of the thicknesses of mica plates and the wavelengths at which they act as quarterwave or halfwave phase retarders. Birefringence is found to decrease gradually from −0.0040 at 420 nm to −0.0046 at 700 nm in conformity with pertinent independent experimental results.