Large Faraday effect and structural properties of heavily Tb3+-doped borogermanate glasses: a potential precursor of magneto-optical fibers

Abstract New glass compositions containing high concentrations of Tb 3+ ions were developed aiming at the production of magneto-optical (MO) fibers. This work reports on the structural and MO properties of a new glass composition based on (100- x )(41GeO 2 -25B 2 O 3 -4Al 2 O 3 -10Na 2 O-20BaO) – x Tb 4 O 7 . Morphological analysis (HR-TEM) of the sample with the highest concentration of Tb 3+ ions confirmed the homogeneous distribution of Tb 3+ ions and the absence of nanoclusters. All the samples presented excellent thermal stability against crystallization (ΔT > 100 o C). An optical fiber was manufactured by a fiber drawing process. The UV-Vis spectra of the glasses showed Tb 3+ electronic transitions and optical windows varying from 0.4 to 1.6 µm. The magneto-optical properties and the paramagnetic behaviors of the glasses were investigated using Faraday rotation experiments. The Verdet constant (V B ) values were calculated at 500, 650, 880, 1050, 1330, and 1550 nm. The maximum V B values obtained at 650 and 1550 nm for the glass with x = 18 mol% were − 128 and − 17.6 rad T − 1 m − 1 , respectively. The V B values at 500 and 1550 nm for the optical fiber containing 8 mol% of Tb 4 O 7 were − 110.2 and − 9.5 rad T − 1 m − 1 , respectively, while the optical loss at around 880 nm was 6.4 dB m − 1 .