Ultra-broadband red to NIR photoemission from multiple bismuth centers in Sr₂B₅O₉Cl:Bi crystal

Bismuth (Bi)-doped materials are a new family of laser materials, and they usually exhibit extremely broad near-infrared (NIR) luminescence in 1000–1700 nm. Therefore, they can be utilized for a new generation of ultra-broadband tunable laser sources and ultra-broadband fiber amplifier. The broadband characteristics of Bi-active NIR luminescence can meet the needs of special wavelength laser sources that rare-earth-doped lasers cannot provide. However, at present, the Bi-doped NIR luminescence materials are mainly concentrated on glass, while Bi-doped NIR luminescence laser crystals are rarely reported. In this work, a novel Bi-doped crystal Sr2B5O9Cl:Bi is reported with NIR luminescence, which exhibits broadband absorption in ultraviolet and visible regions, and can produce ultra-broadband from red to NIR luminescence covering 600–1600 nm. The results of excitation, emission spectra, and fluorescence lifetime show that the Sr2B5O9Cl:Bi crystal contains three different Bi-active NIR emission centers. This work could enrich our understanding on Bi NIR emission behaviors in crystals. And this material provides a possibility for the development of a new laser source.