Dispersion of the Refractive Indices of LiNbO₃ Crystal between 20° and 900°C

Abstract

The refractive indices of lithium meta-niobate single crystal were measured with a prism up to 900°C over a wave length range from 420 to 670 mµ. The temperature dependence of the extraordinary refractive index n e is marked in contrasts with small change of the ordinary one n 0 . At 670 mµ, they take values n e =2.191 and n 0 =2.279 at room temperature and amount to 2.283 and 2.296 at 900°C, respectively. The results were discussed in connection with the effect of thermal expansion and the spontaneous polarization of ferroelectric LiNbO 3 .