Ultrabroadband near-Infrared Photoemission from Bismuth-Centers in Nitridated Oxide Glasses and Optical Fiber

Abstract

Wideband NIR-emitting materials are crucial components in light sources and tunable lasers for sensing, metrology, and optical amplification. While traditional rare-earth (RE) doped gain media have reached their limit in bandwidth, Bismuth-doped glasses have been evolving as an interesting alternative with unmatched spectral performance. However, serious issues remain for this type of material, in particular, in achieving the desired spectral bandwidth while providing the ability of fiber drawing on part of the matrix glass, and in terms of stabilization of the active Bismuth center in secondary processing steps at high temperature. Here, we report on chemical nitridation of Bidoped glasses as a means to enhance local network rigidity and, thus, stabilize the NIR active emission species and increase Birelated NIR emission efficiency. At the same time, we show that the existence of nitride bonds leads to the emergence of germanium-related Bi emission centers, which further enhance the spectral bandwidth of Bidoped optical emitters to >600 nm. Beating previous materials, the emission band envelope spans the complete NIR region, that is, from the transparency windows of biological tissue over the low-loss O-band of optical communication which is hardly accessible with typical RE-based materials to the more common C- and L-bands. For demonstration purpose, optical fiber is manufactured from nitridated, Bidoped germanate glass through the rod-in-tube-technique, with NA ∼ 0.14 and stable NIR emission from germanium-related Bi emission centers. This shows how nitridation offers new potential in the design of Bibased optical amplifiers and tunable lasers, and the exploration of novel photonic materials.