Magneto‐optical effect of rare‐earth‐rich borate glasses prepared using a levitation technique

The magneto‐optical properties of rare‐earth‐rich borate glasses prepared using a levitation technique were thoroughly investigated. Among the series of rare‐earth borate glasses, Tb2O3–B2O3 and Dy2O3–B2O3 glasses displayed remarkably large Faraday effects in the visible region. The Verdet constant of 58Tb2O3–42B2O3 reached −229 rad/T·m at 633 nm, surpassing the value of commercially available single‐crystalline Tb3Ga5O12. Compositions with a higher rare‐earth oxide content (60 mol%) than that of binary glasses facilitated the successful synthesis of Tb2O3–Dy2O3–B2O3 ternary glasses. The Verdet constant linearly increased with increasing Tb2O3 content for the glasses with 40 mol% B2O3. Results indicate that rare‐earth‐rich borate glasses are promising candidates for magneto‐optical applications in the visible region, and that the types and amounts of rare‐earth ion mainly affect these properties.