Tm3+ 掺杂ZrF4 -BaF2 -LaF3 -AlF3 -NaF-PbF2玻璃激光制冷中荧光再吸收效应的理论分析

固体材料的激光制冷是近年来发展起来的一个新的研究领域. 掺Tm³⁺的ZrF₄-BaF₂-LaF₃-AlF₃-NaF-PbF₂(ZBLANP)玻璃材料是激光冷却的典型材料之一. 与另一种制冷掺杂离子Yb³⁺相比,Tm³⁺具有更好的制冷潜力. 目前制约材料制冷的一个主要机理就是荧光再吸收. 首先根据Tm³⁺:ZBLANP的光谱参数,利用半经典的随机行走模型得到了不同情况下的平均荧光再吸收次数,随后分析了荧光光子界面出射的全反射效应,并对所得结果进行了修正. 计算结果表明,荧光再吸收会导致量子效率降低0.5%-1%,出射荧光波长红移达到2-10 nm,激光制冷的效率和功率降低. 为了有利于荧光出射和净制冷的实现, 宜采用小体积细长棒的制冷元. 关键词： 激光制冷 稀土离子 荧光再吸收

Fluorescence reabsorption analysis on laser cooling of Tm3+ doped ZrF4 -BaF2 -LaF3 -AlF3 -NaF-PbF2 glass

Laser cooling of solid material has become a new developing research area in recent years. Tm³⁺ doped ZrF₄-BaF₂-LaF₃-AlF₃-NaF-PbF₂ glass is one of the hot materials in this field. Compared with Yb³⁺, Tm³⁺ has better cooling potential. Up to date, one of the main factors restricting the cooling effect is fluorescent reabsorption. In this paper, firstly, using several spectral parameters of Tm³⁺, the reabsorption effect is calculated by stochastic model which is a semianalytical approach to this problem. The average number of absorption events is obtained. Afterwards, the effect of fluorescence trapping due to total internal reflection is analyzed. The results show that the quantum efficiency will be lowed by 0.5%-1% due to reabsorption, that the redshift of the mean fluorescence wavelength is in the range of 2-10 nm, and that the cooling efficiency and the cooling power decrease. Finally, after discussion, we find that the use of a small size and a long thin geometry will benefit to the fluorescence emission and cooling effect.