Al3+/Yb3+/P5+掺杂对石英玻璃紫外透过和紫外激发荧光的影响

采用溶胶-凝胶法结合高温真空烧结工艺制备了不同浓度的Al³⁺/Yb³⁺/P⁵⁺掺杂石英玻璃。研究了P⁵⁺和Al³⁺的引入对Yb³⁺掺杂石英玻璃紫外透过和紫外激发荧光光谱, 以及Yb4d电子结合能的影响, 并初步探索了其机理。研究结果表明, Al³⁺/Yb³⁺/P⁵⁺掺杂石英玻璃在190~300 nm波段的吸收主要来源于O^2-→Yb³⁺的电荷迁移吸收, 其谱带位置和Yb4d电子结合能随Yb³⁺的第二配位元素(Al、Si、P)电负性增大向高能方向移动。真空烧结条件下, 引入Al³⁺会引发石英玻璃中Yb³⁺还原为Yb²⁺, 其典型的吸收峰位于330 nm处; 然而, 在Al³⁺/Yb³⁺共掺的基础上再引入P⁵⁺, 且P⁵⁺/Al³⁺摩尔比大于1时, 可以有效抑制Yb²⁺的形成。紫外光激发引起的近红外发光(976 nm)是电子从电荷迁移态弛豫到Yb³⁺激发态向基态跃迁的结果, 可见发光(525 nm)归因于Yb²⁺的5d→4f跃迁。本文研究结果对通过优化工艺和调整组分制备出高性能的Yb³⁺掺杂光纤具有一定的指导意义。

Influence of Al3+/Yb3+/P5+-doping on UV Transmission and Fluorescence Spectra under the UV Excitation of Silica Glasses

Silica glasses containing different contents of Al₂O₃, Yb₂O₃ and P₂O₅ were fabricated by Sol-Gel method combined with high temperature vacuum sintering. Changes in UV transmission, fluorescence spectra under the UV excitation, and X-ray photoelectron spectra (XPS) of Yb4d caused by P⁵⁺ and Al³⁺ ions co-doping in Yb³⁺-doped silica glasses were comparatively investigated. The related mechanisms were discussed. Results show that the strong absorption bands in the range of 190 nm to 300 nm in Al³⁺/Yb³⁺/P⁵⁺-doped silica glasses are largely due to the charge-transfer (CT) from O^2- to Yb³⁺, the positions of CT-absorption bands as well as binding energy of Yb4d are shifted to the higher energy with increasing electro-negativity of the second coordination element (Al, Si, P) of Yb³⁺ ions. In addition, introduction of Al³⁺ into Yb³⁺-doped silica glass leads to the reduction of Yb³⁺ to Yb²⁺ ions under vacuum sintering condition. The characteristic absorption of Yb²⁺ ions is located at 330 nm. Nevertheless, further incorporation P⁵⁺ into Al³⁺/Yb³⁺-co-doped silica glass with mole ratio of P⁵⁺/Al³⁺>1 can effectively suppress the formation of Yb²⁺. The IR luminescence (976 nm) under UV excitation originates from a relaxed CT transition, and the visible luminescence (525 nm) is ascribed to 5d→4f transition of Yb²⁺. The results provide a guidance on technology optimization and composition design for fabricating high-performance Yb³⁺-doped fiber.