稀土粉末Eu:Y2O3的自由感应衰减量子拍

稀土固体是重要的激光和光电子材料。目前,由于以宽带信号和太赫兹比特数据传输率为特征的信息技术的发展,稀土固体材料的相干瞬态动力学过程成为宽带与高速信息光子学的基本物理问题之一。研究了室温下稀土粉末样品Eu³⁺:Y₂O₃自由感应衰减的相干瞬态光谱,这有助于理解有效的光吸收动力学、激发态弛豫、相干能量传递和超短光脉冲在稀土固体中的传播。用一对紫外飞秒相干光脉冲作用于稀土粉末样品Eu³⁺:Y₂O₃,然后监测物质激发态的布居数随两个激发脉冲之间的延时的变化,测量到其自由感应衰减量子拍(FID),从拍频周期分析确定了其能级精细结构,能级的退相时间长达皮秒量级。理论分析和实验结果符合得很好。对稀土离子的量子干涉的研究,表明其在受激受控光放大方面具有潜在的应用前景。

Free Induction Decay Quantum Beating in Eu:Y2O3 Powder

Rare earth solids are important materials widely used in optoelectronics. The notable examples are Nd:YAG as laser materials and Er doped fiber as optical amplifier for optical communication. The ultrafast properties of rare earth materials have not been extensively studied before. However, due to the present development of information technology characterized with broadband signals and tera bit rate data transmission, it is very important to understand the interaction between the rare earth ion and its solid environment, and their corrected role in the coherent dynamic processes. In trivalent rare earth solids, the optically active center involves intra-4f electron transitions. The 4f electrons are well shielded from the crystalline environment by their outer 5s5p electrons. The resulting sharp absorption or emission spectra indicate long surviving optical coherence among various 4f electronic states even at room temperature. We report both time domain and frequency domain linear spectroscopies in the study of coherent dynamic in rare earth powder Eu³⁺:Y₂O₃ at room temperature. The time domain free induction decay was obtained via an interferometric fluorescence measurement with a pair of phase corrected femtosecond pulses, while the frequency domain signal is via steady state fluorescence excitation. The recorded interferogram exhibits beatings in picosecond time scale arising from the interferences among various weakly split of 4f electronic states. The separation of the involved energy levels deduced from the beating is approximately 1.1 nm, in agreement with that obtained from the excitation spectra. Analysis with the theory of multi level excitation resulted quantum interference shows that the experimental results can be well explained. Rare earth is often used as gain medium of laser, one gain curve include many stark split electronic levels. The long coherent relaxation time indicates its possible to enhance the population of one electronic level while depressing the population of other electronic levels by quantum interference control. The research on quantum interference of rare earth ions shows its potential application in stimulated light amplification.