High Verdet constant of TbO-doped TiO-BO-AlO-NaO magneto-optical glass.

Tb-doped magneto-optical (MO) glass is widely used in fiber optics, optical isolators, and modulators. However, only the paramagnetic Tb ions exhibit significant MO effects, whereas the diamagnetism Tb ions suppress the MO effects. Therefore, the valence state control of Tb ions is very critical to optimize MO performance. Here, a reduction strategy was introduced to adjust the Tb valence in glass to achieve the high MO effect. The TiO, which has low valence Ti ions and good reducibility, was used to suppress the oxidation of Tb to Tb ions. In the TiO-BO-AlO-NaO glass, 10 mol% TiO can increase the Verdet constant at 650 nm by 19%. With the further increase in TbO concentration, the Verdet constant reaches a high value of 117 rad/(T·m) at 650 nm, which is close to the Verdet constant of TGG crystal (121 rad/(T·m)). This work provides a new approach to increase the Verdet constant of MO glass.