Origin of broad NIR photoluminescence in bismuthate glass and Bi-doped glasses at roomtemperature

Abstract

Bi-doped glasses with broadband photoluminescence in the near-infrared (NIR) spectralrange are presently receiving significant consideration for potential applications intelecommunications, widely tunable fiber lasers and spectral converters. However, theorigin of NIR emission remains disputed. Here, we report on NIR absorption andemission properties of bismuthate glass and their dependence on the meltingtemperature. Results clarify that NIR emission occurs from the same centers as itdoes in Bi-doped glasses. The dependence of absorption and NIR emission ofbismuthate glasses on the melting temperature is interpreted as thermal dissociation ofBi2O3 into elementary Bi. Darkening of bismuthate glass melted at1300 °C is due to the agglomeration of Bi atoms. The presence of Bi nanoparticles isconfirmed by transmission electron microscopy, high-resolution energy dispersivex-ray spectroscopy and element distribution mapping. By adding antimony oxideas an oxidation agent to the glass, NIR emission centers can be eliminated andBi3+ is formed. By comparing with atomic spectral data, absorption bands at∼320 ,∼500 , 700 , 800 and 1000 nm observed in Bi-doped glasses are assigned toBi0 transitions , , , and , respectively, and broadband NIR emission is assigned to the transition .