COMPLEX REFRACTIVE-INDEX OF MGO IN THE FAR INFRARED FROM TRANSMISSION AND REFLECTION MEASUREMENTS

Transmittance and reflectance spectra of single crystal MgO are reported at different temperatures ranging from 295 to 20 K, in the frequency range 25-500 cm-1. At 20 and 295 K reflectance spectra were also measured up to 800 cm-1. From these data we derive temperature and frequency dependence of the real (n) and imaginary (k) part of the complex refractive index of MgO. At low frequencies, where both transmittance and reflectance spectra were measured, reliable n and k data are directly derived from the measured spectra. At high frequencies, where only reflection measurements are possible, n and k are derived, as usual, by fitting model profiles to the experimental ones.