D2d对称性晶格环境中Yb离子的共振吸收与特征激光发射行为研究

Our recent studies show that quasi-three-level lasers such as Yb ion possess characteristic laser emission behavior, which is determined by the saturation nature of their resonant absorption. This saturation nature is closely related to the symmetric lattice environment of the Yb ion and the interaction between its optically active electrons and the host crystal. The lattice environment with D2d point group symmetry is most likely to make the Yb ion exhibit its intrinsic various characteristic laser emission properties. In this project we plan to conduct investigations into the resonant absorption of Yb ions doped into the orthophosphates and arsenates having a D2d lattice environment, in order to reveal the intrinsic connections between the saturation nature of the resonant absorption and the electron-phonon coupling, vibronic transition, Raman scattering of phonons, and dipole-dipole interaction between Yb ions existing in the crystal, to explore steady-state characteristic laser emission behavior and dynamical laser properties such as self-Q-switching and self-mode-locking of the Yb ion in these crystals, and to develop novel Yb ion laser crystals. It is expected that the research proposed in this project will lead to an exact, deep, and thorough understanding of quasi-three-level lasers like Yb ion, improving the relevant theory in laser physics, providing instructive hints for the development of novel solid-state lasers, and promoting to some extent the research and development in relevant areas including condensed mater physics, crystal materials, and laser technology.

前期研究表明，Yb离子等准三能级系统存在着由其共振吸收的饱和性质所决定的特征激光发射行为。这一共振吸收的饱和性质与Yb离子所处的对称性晶格环境及其光学活性电子与基质晶体的微观作用密切相关。具有D2d点群对称性的晶格环境，最有可能使Yb离子呈现其固有的多样性特征激光发射行为。本项目将对具有D2d晶格环境的正磷酸盐和砷酸盐晶体中Yb离子的共振吸收开展系统研究，揭示共振吸收的饱和性质与晶体内电子-声子耦合、振动-电子跃迁、声子Raman散射以及Yb离子之间的偶极相互作用等微观过程的内在联系，探索这些晶体中Yb离子的稳态特征激光发射行为及自调Q、自锁模等动态激光发射特性，发展新型Yb离子激光晶体。本项研究可望获取对Yb离子等准三能级激光系统全面、准确和深刻的认识，完善激光物理学的相关理论，为新型固态激光器的研发提供有益的启示，并在一定程度上推动凝聚态物理学、晶体材料以及激光技术等相关领域的发展。

具有D2d局域对称性晶格环境的稀土正磷酸盐、钒酸盐和砷酸盐，对于Yb离子有着十分特别的意义。在这类基质晶体中，Yb离子可望呈现出某些不同寻常的激光发射行为和特性。本项目工作对掺Yb稀土正磷酸盐和部分钒酸盐晶体的生长、光谱学性质、共振吸收及其饱和性质、连续波稳态激光发射性质、调Q脉冲动态激光发射特性等开展了较为全面和深入的实验研究；探索发展了利用自发成核由高温溶液中沿结晶学a轴生长薄片状和沿结晶学c轴生长微柱状稀土正磷酸盐晶体的方法和技术；由厚度为亚毫米的薄片晶体制成的微片激光器可产生1～5 W的连续波或脉冲输出功率，而由横向尺寸为亚毫米的微柱状晶体制成的微棒激光器则能够产生5～10 W的连续波或脉冲激光输出，这为发展1-um近红外波段小型或微型高功率全固态激光器提供了一种新的可能途径。本项研究还表明，与晶体对称性相比，基质晶体中Yb离子配位体的性质、共价效应、电子-声子相互作用、声子频谱和态密度等对于激光晶体的光谱学性质和激光发射特性有着更为重要甚至关键性的影响。