Conversion Mechanism From Trivalent Bismuth to Bivalent Bismuth Defect Center in Bi-Doped Silica Optical Fiber

We present first-principle methods on the conversion of trivalent bismuth center in Bi-doped silica optical fiber. With the increase of Bi-O distance in different member rings, the reaction energy of transition state configurations gradually become larger. The reaction energy of Bi-6MR is greater than that of Bi-4MR, than that of Bi-5MR, respectively. Based on the basis of the time-dependent density functional theory (TDDFT), transition energy levels of bivalent bismuth defect center models are investigated. Our calculations reveal that the similar to 1310 nm luminescence of the second optical communication window is likely caused by bivalent bismuth defect center configuration.