Al^(3+)/Yb^(3+)/P^(5+)掺杂对石英玻璃紫外透过和紫外激发荧光的影响

Influence of Al^(3+)/Yb^(3+)/P^(5+)-doping on UV Transmission and Fluorescence Spectra under the UV Excitation of Silica Glasses

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Al^(3+)/Yb^(3+)/P^(5+)掺杂石英玻璃。研究了P^(5+)和Al^(3+)的引入对Yb^(3+)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,Al^(3+)/Yb^(3+)/P^(5+)掺杂石英玻璃在190~300 nm波段的吸收主要来源于O2-→Yb^(3+)的电荷迁移吸收,其谱带位置和Yb4d电子结合能随Yb^(3+)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Al^(3+)会引发石英玻璃中Yb^(3+)还原为Yb2+,其典型的吸收峰位于330 nm处;然而,在Al^(3+)/Yb^(3+)共掺的基础上再引入P^(5+),且P^(5+)/Al^(3+)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Yb^(3+)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Yb^(3+)掺杂光纤具有一定的指导意义。

Silica glasses containing different contents of Al2O3, Yb2O3 and P2O5 were fabricated by Sol-Get method combined with high temperature vacuum sintering. Changes in UV transmission, fluorescence spectra under the UV excitation, and X-ray photoelectron spectra （XPS） of Yb^4＋ caused by P^5＋ and Al^3＋ ions co-doping in Yb^3＋-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 Al^3＋/Yb^3＋/P^5＋-doped silica glasses are largely due to the charge-transfer （CT） from O^2- to Yb^3＋, the positions of CT-absorption bands as well as binding energy of Yb^4＋ are shifted to the higher energy with increasing electro-negativity of the second coordination element （Al, Si, P） of Yb^3＋ ions. In addition, introduction of Al^3＋ into Yb^3＋-doped silica glass leads to the reduction of Yb^3＋ to Yb^2＋ ions under vacuum sintering condition. The characteristic absorption of Yb^2＋ ions is located at 330 nm. Nevertheless, further incorporation P^5＋ into Al^3＋/Yb^3＋-co-doped silica glass with mole ratio of P^5＋/Al^3＋〉1 can effectively suppress the formation of Yb^2＋. 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 Yb^2＋. The results provide a guidance on technology optimization and composition design for fabricating high-performance Yb^3＋-doped fiber.