Ho^(3+)/Yb^(3+)共掺碲酸盐玻璃的上转换发光及能量传递机理

Upconversion emission and energy transfer mechanism of Ho^(3+)/Yb^(3+) co-doped tellurite glasses

用高温熔融法制备了Ho3+单掺和Ho3+/Yb3+共掺、组分为TeO2-ZnO-Na2O的碲酸盐玻璃,应用Judd-Ofelt(JO)理论计算分析了玻璃的强度参数Ωt(t=2,4,6)、自发辐射跃迁几率A、荧光分支比β和荧光辐射寿命τrad等各项光谱参数。通过测量上转换光谱,着重研究了Yb3+掺杂对于Ho3+上转换发光性能的影响,分析了Yb3+/Yb3+以及Yb3+/Ho3+间的能量传递过程。结果显示,975nm泵浦下Ho3+的上转换发光主要来自于Yb3+/Yb3+间的共振能量传递以及基于单声子和双声子辅助的Yb3+/Ho3+间的能量传递过程,并计算得到了声子贡献比和能量传递微观参数。同时,计算分析了Ho3+:5 I7→5 I8能级跃迁的吸收截面、受激发射截面和增益系数。研究表明,Yb3+/Ho3+共掺TeO2-ZnO-Na2O玻璃可以作为上转换激光器和2.0μm波段固体激光器的潜在增益基质。

Ho^3＋ single-doped and Ho^3＋/Yb^3＋ co-doped tellurite glasses with the composition of TeO2- ZnO-Na2 O were prepared by melt-quenching method. The intensity parameters Ωt （t= 2,4,6）, spontaneous radiative transition rate A, fluorescence branching ratio β and radiative lifetime τrad of Ho^3＋ are calculated based on the measured absorption spectra with the Judd-Ofelt theory. The influence of Yb^3＋ doping on the Ho^3＋ upconversion emission is investigated through the measurement of upconversion spectra,and the energy transfer mechanisms between the Yb^3＋/Yb^3＋ and Yb^3＋/Ho^3＋ ions are analyzed in detail. The results show that the upconversion emission of Ho^3＋ ions under 980 nm diode laser excitation is mainly the result of energy transfers：first the resonant energy transfer from Yb^3＋ to Yb^3＋ ions,and then the one and two phonon-assisted nortresonam energy transfer from Yb^3＋ to Ho^3＋ ions. The energy transfer coefficient and phonon contribution for the above energy transfer process are calculated and analyzed. Meanwhile, the absorption, emission cross-sections and gain coefficient of Ho^3＋ ： ^5 I7 →%5 I8 transitions are calculated. The research shows that the Yb^3＋/Ho^3＋ co-doped TeO2-ZnO-NazO glass is a promising host material applied for upconversion laser and 2.0μm-band solid iaser.