Refractive index and optical dispersion of rare earth oxides using a small-prism technique

Abstract

Crystals of cubic Sc 2 O 3 , Lu 2 O 3 , Yb 2 O 3 and Dy 2 O 3 were grown as single-crystal fibres of dimensions of ~0.5 mm×15 mm using the laser-heated pedestal growth technique. Refractive indices of prisms prepared from these fibres were measured at wavelengths of 435.8-643.8 nm and were used to calculate n at λ = 589.3 nm ( n D ) and at λ = ∞ ( n ∞ ) using the one-term Sellmeier equation 1/( n 2 -1) = - A /λ 2 + B . In addition, using the dispersion of two refractive indices of a larger crystal of monoclinic Gd 2 O 3 :Nd, we have estimated mean values of ⟨ n ∞ ⟩ and ⟨ n D ⟩. Total polarizabilities, α total , were calculated from n ∞ and the Lorenz-Lorentz equation. Refractive indices, n D , and dispersion values, A , were, respectively, 1.9943 and 66 for Sc 2 O 3 , 1.9349 and 66 for Lu 2 O 3 , 1.9470 and 68 for Yb 2 O 3 , 1.9757 and 73 for Dy 2 O 3 and ⟨2.086⟩ and 62×10 -16 m 2 for Gd 2 O 3 :Nd. These data were used to estimate the refractive indices and total polarizabilities of cubic Tm 2 O 3 , Er 2 O 3 , Ho 2 O 3 , Tb 2 O 3 , Gd 2 O 3 and Eu 2 O 3 , monoclinic Sm 2 O 3 and hexagonal Nd 2 O 3 from plots of the type α total = a (atomic number) + b .