Tb₂O₃/Ce₂O₃-Codoped B₂O₃–Ga₂O₃(Al₂O₃) Glasses with a Large Faraday Effect Synthesized via Containerless Method for Small Optic Isolators

Magneto-optical (MO) glasses with a high Verdet constant and a wide transparency window are of fundamental significance for multifunctional applications. However, the Faraday effect can be affected by the effective content and valence-state variation of rare-earth ions. Herein, a strategy of introducing Ce₂O₃ to rationally reduce part of Tb⁴⁺ to Tb³⁺ and using a levitation technique to embed high-content paramagnetic ions into glass is proposed herein to improve the MO response. Tb₂O₃/Ce₂O₃-codoped glasses with different Tb₂O₃ contents are characterized by good thermal properties (<i>T</i>_g ≥ 778.4 °C), large Faraday effect, high density (ρ ≥ 6.7496 g/cm³), physical stability, and transmittance. Typically, the glasses are highly transparent over a wide spectral window such that the transmittances at 633 and 1064 nm can also exceed 74%. Moreover, the obtained MO glasses incorporated with high Tb₂O₃ contents exhibit remarkably high Verdet constants at 25 °C ranging from -198.8 ± 14.6 to -202.6 ± 13.6 rad/(T·m) at 633 nm, -68.5 ± 4.3 to -77.4 ± 1.1 rad/(T·m) at 1064 nm, and -14.7 ± 1.1 to -15.1 ± 0.7 rad/(T·m) at 1550 nm, exceeding the values of the commercial Tb₃Ga₅O₁₂ crystal. Measurements of the extinction ratio, valence state of Tb element, and local glass structure are also carried out and discussed in detail. The results suggest that the glasses are promising candidates in particular for designing innovative MO devices for potential multiband applications.