Intrinsic birefringence in calcium fluoride and barium fluoride

We report measurements of the intrinsic birefringence in ${\mathrm{CaF}}_{2}$ and ${\mathrm{BaF}}_{2}$ for wavelengths in the range 365 nm to 156 nm, and ab initio optical response calculations in these materials and Si, Ge, GaAs, and GaP. Calculations typically agree within 40%. For 〈110〉 propagation, where the effect is largest, our measurements for ${\mathrm{CaF}}_{2}[{\mathrm{BaF}}_{2}]$ give ${n}_{〈1\ifmmode\bar\else\textasciimacron\fi{}10〉}\ensuremath{-}{n}_{〈001〉}=(\ensuremath{-}11.8\ifmmode\pm\else\textpm\fi{}0.4)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}[(+34\ifmmode\pm\else\textpm\fi{}3)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}]$ for $\ensuremath{\lambda}=156.10\mathrm{nm}.$ The magnitudes of these values have serious consequences for the use of crystalline optics in precision optical systems in the ultraviolet, including 193 nm and 157 nm optical lithography.

Перевод пока недоступен