Refractive index measurements of CaF2 single crystal and melt by ellipsometry
Shakhawat H. Firoz, Takashi Sakamaki, Rie Kojima Endo and Masahiro Susa
Refractive indices of CaF2 have been determined by ellipsometry and factors determining the temperature dependence are discussed. Measurements were made on CaF2 single crystal and melt in dehydrated helium atmosphere in the temperature ranges from room temperature to 1050 K and from 1600 K to 1800 K, respectively. The standard deviation in the measured refractive indices was within ±0.001. The following equations were fitted to the measured refractive indices:
Single crystal: n = n298-1 541 x 10-5 (T/K -298) 298 K-1050 K,
melt: n = n1600-4.667 x 10-5 (T/K-1600) 1600 K-1800 K,
where n298 = 1.429 and n1600 =1.409.
It is likely that the temperature coefficients are determined predominantly by those of the densities.