Small photoelastic oxide glasses free from s2-type cations

We report a significant advancement in small photoelastic oxide glasses by investigating barium lanthanum silicate and phosphate glass systems. The photoelastic constants of silicate glasses, which do not contain p-block cations with n = 5 and 6 ns2-type outer shell electrons configurations, are smaller than |0.85 × 10−12| Pa−1 at the wavelength of 633 nm, while the minimum value of phosphate glass exhibits smaller than |0.2 × 10−12| Pa−1, still having good water durability. A simple evaluation of the polarization properties of visible transparent and small photoelastic glasses revealed that the polarization azimuth of linear polarized light is maintained even when a low load of at least 100 N is applied to the glasses. It can be applied to polarization-maintaining optical devices such as small photoelastic glass using ubiquitous elements. The glass structure has been analyzed by means of 29Si and 31P MAS-NMR spectroscopy. While La2O3 modifies the phosphate structure in an expected manner, the silicate network description cannot be obtained with the usual Qn notation, suggesting that La2O3 led to a much more disordered silicate network.