Erbium-Ion-Doped Bismuth Borate Glasses for High Optical Gain NIR Fiber Laser Applications

The study focused on investigating the thermal, structural, and luminescent properties of bismuth borate glasses doped with erbium (Er 3+ ) ions and modified with Gd 2 O 3 , K 2 O, and Li 2 O (BBGKL: Er x ) aiming for fiber lasers. Two glass transition temperatures were observed at 381 (T g1 ) and 471 K (T g2 ) for BBGKL glass. O 1s de-convolution spectrum bridging oxygens for BBGKL glass, including B-O, Bi-O, Li 2 O, and K 2 O, were discovered by XPS. Both the photoluminescence (PL) 4 I 13/2 → 4 I 15/2 NIR and the absorption bands from the UV-visible-NIR spectrum were found to occur at 1531 nm for BBGKL: Er. The luminescence quenching was not noticed up to 3.0 mol% of Er 3+ ion concentration. The BBGKL: Er 0.5 glass has a remarkable connection between its absorbance and emission cross-sections of 0.77 and 0.82 × 10 −20 cm 2 , respectively. The longest lifetime of green emission for the 4 S 3/2 → 4 I 15/2 transition was found for BBGKL: Er 2.0 glass at 10.6 μ s and 1531 nm NIR emission for the 4 I 13/2 → 4 I 15/2 transition of BBGKL: Er 0.5 glass was 0.77 ms. In the 1413–1728 nm NIR band region for BBGKL:Er 3.0 , high optical gain cross-section G( λ ) was promising for the population inversion at γ = 0.6. These findings suggested that the BBGKL: Er 0.5 glass would prove helpful in NIR fiber laser applications.