Effect of Na2O on Verdet constant of Tb-doped magneto-optical glass

The terbium (Tb) ions doped magneto-optical glasses have attracted significant attention due to their high Verdet constant and excellent optical properties. In the Tb ions doped glass, +3 and + 4 valence states of Tb ions coexisted. However, only the +3 valence is favorable for magneto-optical performance. This study proposed a strategy to increase the concentration of Tb3+ ions (CTb3+) in the glass. The high optical basicity Na2O is beneficial for enhancing the Verdet constant. The lower melting temperature suppresses the oxidation of the Tb3+ to Tb4+, leading to the increase of CTb3+. As a result, the Verdet constant at 650 nm was achieved as high as 78.6 rad/(T·m), representing a 42.8 % improvement compared to glasses melted at 1450 °C. This approach avoids glass crystallization at high concentrations of Tb doping and provides a new solution for preparing high-performance magneto-optical glasses.