Nature of Bi-related near IR active centers in glasses: state of the art and first reliable results

Abstract

Despite the great success in the development of the Bi-doped fibers technology and the creation of Bi-doped fiber lasers and optical amplifiers, some problems are not solved yet. The main problem is that the nature of bismuth NIR emitting centers is not clear. At present, a number of hypotheses are published, but none of them have been directly confirmed. The aim of this letter is to discuss briefly some of the existing hypotheses and to propose our approach concerning the nature of Bi-related NIR active centers. In previous publications we suggest that Bi-related NIR emitting centers are clusters, consisting of Bi ions and oxygen deficiency centers but not Bi ions themselves. In this letter we present the results of our experiments which confirm this structure of the Bi NIR active centers in germanosilicate fibers.