Low-temperature preparation and optical properties of Bi/Al co-doped silica glass

TLDR: In this article , an optimized sol-gel method was used to synthesize co-doped silica glass with a relatively high Bi concentration (0.552 wt.%) using Hydrofluoric acid (HF) as a catalyst.

Abstract: Bismuth (Bi)-doped silica-based glasses and fibers are attractive materials for the new optical amplifiers and tunable lasers. In this paper, Bi/Al co-doped silica glass with a relatively high Bi concentration (0.552 wt.%) were prepared by using the optimized sol-gel method. Hydrofluoric acid (HF) was used as a catalyst in the reaction, which reduced the hydroxyl to lower than 5ppm in the final glass. After the process of drying and sintering, the gel was turned into the transparent glass at low temperature (~1300 °C). The optical properties of Bi/Al co-doped silica glass were also investigated. Excited by a 980 nm laser diode, broadband fluorescence centered at 1114 nm was obtained, which was ascribed to the Bi-Al active center (BAC-Al). The emission cross-section (𝜎𝑒𝑚) was calculated to be 7.4 × 10−21 cm2 for BAC-Al. In addition, ultra-broadband emission ranging from 850 nm to 1700 nm was also obtained excited by the 808 nm LD, which might be ascribed to BAC-P overlapped by other BACs. After the gaussian separation of fluorescence peak, the emission cross-section for BAC-P was 13.4×10−21 cm2. Our results confirmed the potentialities of the optimized sol-gel method in Bi-doped glass fabrication. The Bi/Al co-doped silica glass prepared in this work were promising to develop Bi-doped fibers and relative devices.