ホウ酸塩ガラスの高屈折率低分散性に及ぼす高原子価イオンの添加効果

抄録

Refractive indexes of barium borate-based glasses were measured in the wavelength range from 0.265 to 1.710μm by using the minimum deviation method. Factors affecting the refractive index dispersion are discussed by using the single-oscillator Drude-Voigt equation. Borate glasses are characterized by the larger number N of molecules in a unit volume than that for silicate glasses. The feature of borate glasses, that is, relative high refractive index and low dispersion, is dominated by the number N which is related to the fraction of four-coordinated borons estimated by Green-blatt and Bray. Borate glasses containing high valency cations, e.g., Y³⁺, La³⁺, Ti⁴⁺, Nb⁵⁺, Ta⁵⁺, posess higher refractive indexes and higher dispersion than barium borate binary glasses.