Fabrication and characterization of highly Dy3+- and Tb3+-doped germano-borate glasses for magneto-optic device applications at 1.55 μm

Highly Dy ³⁺- and Tb ³⁺-doped germano-borate glasses with different rare-earth ion concentrations (10−25 mol%) were fabricated and their thermal, thermo-mechanical, optical, and magneto-optic (MO) properties were investigated with respect to the rare-earth ion concentration. The glasses showed high transmission properties of > 83% in the near-infrared regions of approximately 1.5 and 2.1 μm. The MO properties of the glasses were investigated using Faraday rotation measurements at 1.5 μm. The large Verdet constants of −5.35 and −6.11 rad/(T•m) at 1.55 μm were obtained for the glasses incorporated with the highest Dy ³⁺ and Tb ³⁺ concentrations of 25 mol% and 16 mol%, respectively; this was due to large effective magnetic moments and electronic transition frequencies of the rare-earth ions. The results showed that the germano-borate glasses doped with high Dy ³⁺and Tb ³⁺ concentrations are promising MO materials for application in MO devices in the near-infrared region.