脉冲强磁场下铒掺杂钒酸钇单晶发光巨增强效应的机理研究

Erbium doped materials exhibit many novel optical properties under high magnetic fields, such as photoluminescence (PL) enhancement, PL suppression, and PL energy transferring. Recently, we have observed an extraordinary magnetic field induced PL enhancement effect in Er3+:YVO4 single crystals for the first time. It is important to understand the origination of this phenomenon and control the generation of such effects in different Lanthanide ion doped materials for future designing of magnetic-controlled devices and magnetic-based sensors. According to these novel and interesting magneto-optical properties, this proposal will investigate the evolution characters of different PL emission bands in Er3+:YVO4 single crystals under different excitation conditions with magneto-optical PL setup, and the absorption spectra of the excitation transition with magneto-absorption measurement setup under pulsed high magnetic fields. And the influences of the crystal direction, temperature, erbium ion doping concentration on the PL enhancement will also be considered. The dynamics property of the PL versus the sweeping rate of the magnetic field will be investigated using a setup which has the functions of both magneto-PL and magnetization measurements. Crystal field theory with magneto parameters will be used to do numerical calculations. The achievement of goal in the project will not only reveal the mechanism of these significant phenomena and point out a new way to improve the PL of rare-earth element doped materials, but also promote the application of rare-earth luminescent materials in magnetic-controlled PL devices, magnetic-based sensors, and magnetic field calibration equipments.

铒掺杂化合物因具有磁致发光增强、发光减弱及发光能量转移等特性，在激光晶体、磁场标定和磁场传感等方面有重要应用。申请者近期首次在铒掺杂钒酸钇单晶中观测到高达两个量级的磁致发光巨增强效应。揭示该效应的物理机制，并掌握增强发光的方法，是未来设计磁控发光器件和磁场传感器件的基础。本项目将利用脉冲强磁场下的光致发光系统，研究不同激发条件下铒掺杂钒酸钇单晶的不同发光带随磁场变化的特性；利用强磁场下的吸收谱测量系统，研究样品激发跃迁对应的吸收峰在磁场下的演变规律；探索晶向、温度、光路配置及铒掺杂浓度等因素，对材料磁致发光增强效应的影响；利用磁光和磁化同步测量装置，研究样品发光随磁场变化的动态特性；并利用含磁场参量的晶体场理论模型进行分析。本项目研究将揭示磁场增强铒掺杂钒酸钇单晶发光强度的机理，为提高稀土发光材料的发光强度提供一种新方法，促进稀土发光材料在磁控发光、磁场传感和磁场标定等领域的推广应用。

铒掺杂化合物因具有磁致发光增强、发光减弱及发光能量转移等特性，在激光晶体、磁场标定和磁场传感等方面有重要应用。本项目在前期观测到的磁场诱导铒掺杂钒酸钇单晶在发光巨增强现象基础上，通过对比研究铒掺杂钒酸钇单晶中绿光发光强度和吸收率随磁场变化规律、吸收谱在磁场作用下的劈裂及移动规律、及相同激发条件下绿色发光和中红外发光随磁场变化行为的异同，发现磁场对激发能级的调制（共振激发）是引起发光巨增强效应的主要因素、对发光能级的调制（亚稳态的电子布局数变化）是影响发光强度的次要因素。通过研究铒掺杂浓度、样品晶向、样品温度及激发光功率等因素对铒掺杂钒酸钇在磁场下发光行为的作用规律，揭示出晶体场和电子布居数分布是影响铒掺杂钒酸钇单晶中发光增强峰位置及增强倍数的内在因素。通过对照研究铒掺杂钒酸钇和钒酸钆单晶在强磁场下发光增强行为的不同，总结出样品的基质材料及其对应的晶体场分布情况与磁场诱导发光增强行为密切相关，可以通过设计基质材料并调控晶体场分布函数来调控磁致增强峰所对应的磁场强度。利用晶体场理论计算了铒掺杂钒酸钇单晶的精细电子能级结构和朗德劈裂因子，从理论上预期了各个磁致增强发光峰所对应的磁场强度，理论预期结果和实验完全一致。总之，本项目的成功实施揭示了磁场调控稀土发光材料发光行为的物理机制；发明了一种提高稀土发光材料的发光强度的新方法，并最终将推动稀土发光材料在磁控发光、磁场传感和磁场标定等领域的应用。