Study on the Structural, Optical, and Magneto-Optical Properties of Bi2O3-Pb3(BO3)2-Ga2O3-PbO Glasses for Temperature-Insensitive Magneto-Optical Isolator Applications

In this work, bismuthate glasses with compositions of 64Bi₂O₃-(25-x)Pb₃(BO₃)₂-11Ga₂O₃-xPbO (where x = 2, 7, 12, 17) were prepared by the melt-quenching method, and their density, thermodynamic stability, Raman spectra, X-ray photoelectron spectra, Verdet constant, and nanosecond laser-induced damage threshold (LIDT) were characterized. As the content of PbO increases, the thermodynamic stability and laser-induced damage threshold of the glass gradually decrease, which corresponds to the increase in the glass's optical basicity, the rise in non-bridging oxygen content, and the valence state transition of Bi ions observed in structural studies. A relatively large Verdet constant was obtained in the glass with the composition of 64Bi₂O₃-8Pb₃(BO₃)₂-11Ga₂O₃-17PbO, with a value of -0.191 min·G^-1·cm^-1 at a wavelength of 633 nm, which is much larger than that of commercially diamagnetic glasses. In addition, the variation in the Verdet constant at 1064 nm between 20 and 80 °C is less than 0.4 × 10^-5 K^-1, which indicates that these bismuthate glasses are good candidates for magneto-optical devices under thermally unstable conditions.