Refractive properties of magnesium fluoride

The refractive indices of a commercially available specimen of single-crystal MgF2 were determined for both the ordinary and extraordinary rays at selected wavelengths from 0.2026 to 7.04 μm. Measurements were made by means of the minimum-deviation method on a precision spectrometer near 19°C. The experimentally determined index values for each polarization were fitted to a three-term Sellmeier-type dispersion equation of the form n2-1=∑Ajλ2(λ2-λj2), where n is the refractive index, λ is the wavelength of interest, λj is the calculated wavelength of an oscillator, and Aj is the strength of the oscillator at λj. The birefringence was computed as a function of wavelength from the calculated index values obtained for the two polarizations. The dispersion coefficients were also determined for the 0 ray and for the birefringence. The results of this study are compared with previously reported work on the refractive properties of MgF2.