Influence of the monovalent bismuth on optical properties in Bi-doped silica optical fiber

Monovalent bismuth-related centers are studied by using first-principle methods in Bi-doped silica optical fiber. On the basis of 6-membered ring (6MR) model, the nBi-doped 6MR models are constructed for studying geometric and optical properties. With the quantity of monovalent bismuths increasing from one to three in 6MR model, the optical absorption intensity showed a trend of first increase and then decrease. The transition energy levels of monovalent bismuth-related model are studied with the time-dependent density functional theory (TDDFT). Our results showed that the 3P1 → 3P0 transition of Bi + ion gives rise to near-infrared (NIR) luminescence around 1270 nm. •The possible micro-structure of Bi+ was constructed in Bi-doped silica optical fiber.•Bi-cluster will be generated when Bi atoms are excessive and further inhibit the absorption intensity.•The 2Bi-6MR-2 model can give rise to the optical absorptions at ∼500 nm and ∼700 nm.•The NIR luminescence around 1270 nm is due to the 3P1 .→ 3P0 transition of Bi + ion.