基于稀土掺杂氟化物晶体的激光制冷新机制研究

发布时间：2018-08-07 10:17

【摘要】：固体激光制冷又被称为光学制冷,是一种利用激光诱导的反斯托克斯荧光对稀土离子掺杂固体或半导体材料进行制冷的技术。由于其具有紧凑、无振动、无电磁干扰和无污染等优点,可应用于航天器搭载的电子装置的局部制冷,因而受到研究者们的广泛关注。在过去的20年中,光学制冷研究已经取得了长足的发展。但是,为了实现其具体应用,当前光学制冷的性能仍有待于提高,工作波长范围仍有待于拓展。本文以稀土离子掺杂氟化物晶体为例,开展固体激光制冷新机制研究,在完善Ho~(3+)光学制冷理论的基础上,给出若干种改进光学制冷性能的理论模型,包括双频泵浦加强的Ho~(3+)光学制冷,能量传递加强的光学制冷,以及双脉冲泵浦增强的超辐射光学制冷。首先,基于对Ho~(3+)掺杂氟化物晶体发射光谱的分析,将现有的光学制冷模型进行推广,使其能更加精确地描述Ho~(3+)光学制冷过程,并以此模型为基础,导出上转换辅助光学制冷的判据条件。结合Ho~(3+):YLiF4晶体的光谱参数,数值模拟Ho~(3+)光学制冷过程,给出不同背景吸收条件下,制冷功率密度和制冷效率随泵浦光强及掺杂浓度的变化关系;以及不同泵浦波长条件下的最大制冷功率密度和相应的最佳掺杂浓度。接着,研究双频泵浦加强的Ho~(3+)光学制冷。根据Ho~(3+)离子的能级特点,分析各跃迁通道的产热情况,阐明双频泵浦对Ho~(3+)光学制冷性能的改进作用。为双频泵浦的Ho~(3+)光学制冷进行理论建模,导出制冷功率密度和制冷效率的表达式。并针对背景吸收,指出双频泵浦机制的适用范围。结合Ho~(3+):YLiF4晶体的光谱参数,给出不同掺杂浓度样品中,制冷功率密度和制冷效率随两种频率的泵浦激光光强的变化关系;最大制冷功率密度,以及相应的制冷效率和最优泵浦光强。然后,研究能量传递加强的光学制冷。通过分析比对Ho~(3+)单掺和Ho~(3+),Tm~(3+)双掺氟化物晶体在负调谐泵浦条件下的发射光谱,粗略推算Ho~(3+)→Tm~(3+)能量传递过程对系统制冷效率的提升幅度。根据能量传递的速率方程理论对Ho~(3+)-Tm~(3+)能量传递光学制冷进行理论建模,导出制冷功率密度和制冷效率的解析表达式。分析能量传递系数、掺杂浓度、泵浦光强和波长等对双掺光学制冷系统性能的影响。结合Ho~(3+),Tm~(3+):YLiF4晶体的光谱参数,数值模拟Ho~(3+)-Tm~(3+)光学制冷系统的制冷功率密度和制冷效率随共振吸收功率密度的变化关系,并与传统Ho~(3+)光学制冷的情况作对比。利用能量传递的平衡参数,给出能量传递制冷增强幅度随温度的变化规律。最后,研究双脉冲泵浦增强的超辐射光学制冷。在阐明超辐射光学制冷基本原理的基础上,分析双脉冲泵浦机制较之连续-脉冲泵浦机制的优势所在。从闭合λ能级系统的动力学方程出发,导出密度矩阵元的解析解。结合Yb~(3+):YLiF4,Tm~(3+):YILiF4和Ho~(3+):YLiF4晶体的光谱参数,数值模拟利用两种泵浦机制实现的超辐射光学制冷过程,给出超辐射光学制冷功率随温度的变化规律。根据面积定理推算适宜超辐射光学制冷的样品尺寸。讨论采用不同泵浦能级对系统制冷表现的影响,通过合理的近似和理论推导给出超辐射光学制冷泵浦能级的优化选择依据。
[Abstract]:Solid laser refrigeration, also known as optical refrigeration, is a technology that uses laser induced anti Stokes fluorescence to refrigerate the solid or semiconductor materials doped with rare earth ions. Because of its advantages of compact, no vibration, no electromagnetic interference and no pollution, it can be applied to the local refrigeration of the electronic device carried by the aeronautical device. In the past 20 years, the research of optical refrigeration has made great progress. However, in order to realize its application, the performance of optical refrigeration still needs to be improved and the range of working wavelength still needs to be expanded. On the basis of improving the theory of Ho~ (3+) optical refrigeration, some theoretical models for improving the performance of optical refrigeration are given, including double frequency pumped Ho~ (3+) optical refrigeration, energy transfer enhanced optical refrigeration, and double pulse pumping enhanced ultra radiation light refrigeration. First, based on the emission of Ho~ (3+) doped fluoride crystals The existing optical refrigeration model is popularized to make it more accurate to describe the Ho~ (3+) optical refrigeration process. Based on this model, the criterion conditions of the upconversion auxiliary optical refrigeration are derived. Combined with the spectral parameters of Ho~ (3+): YLiF4 crystal, the Ho~ (3+) optical refrigeration process is numerically simulated, and the different background absorption conditions are given. The relationship between the cooling power density and the cooling efficiency with the change of the pump light intensity and the doping concentration; and the maximum cooling power density and the corresponding optimum doping concentration under different pumping wavelengths. Then, the Ho~ (3+) optical refrigeration strengthened by double frequency pump is studied. The heat production of various transition channels is analyzed according to the energy level characteristics of Ho~ (3+) ions. The effect of the dual frequency pump on the performance of Ho~ (3+) optical refrigeration is improved. A theoretical modeling for the dual frequency pumped Ho~ (3+) optical refrigeration is made. The expression of the power density and efficiency of the refrigeration is derived. The application range of the dual frequency pump mechanism is pointed out. The application range of the dual frequency pumping mechanism is pointed out. The different doping concentration samples are given with the spectral parameters of the Ho~ (3+): YLiF4 crystal. In the product, the relationship between the cooling power density and the cooling efficiency with the intensity of the pumped laser at two frequencies; the maximum refrigeration power density, the corresponding refrigeration efficiency and the optimal pump light intensity. Then, the optical refrigeration of the enhanced energy transfer is studied. By analyzing the ratio of Ho~ (3+) and Ho~ (3+), Tm~ (3+), double doped fluoride crystals in negative tuning pumps The emission spectrum of the Ho~ (3+) - Tm~ (3+) energy transfer process is roughly calculated. The theoretical modeling of Ho~ (3+) -Tm~ (3+) energy transfer optical refrigeration is modeled based on the rate equation theory of energy transfer, and the analytical expression of the refrigeration power density and refrigeration efficiency is derived. The energy transfer coefficient is analyzed, and the addition of the energy transfer coefficient is analyzed. The influence of impurity concentration, pumping intensity and wavelength on the performance of the dual optical refrigeration system. Combined with the spectral parameters of Ho~ (3+), Tm~ (3+): YLiF4 crystal, the relation between the cooling power density and the refrigeration efficiency of the Ho~ (3+) -Tm~ (3+) optical refrigeration system with the change of the resonance absorption power density is numerically simulated and compared with the traditional Ho~ (3+) optical refrigeration. Using the equilibrium parameters of energy transfer, the law of the amplitude of energy transfer enhancement with the temperature is given. Finally, the double pulse pump enhanced ultra radiation optical refrigeration is studied. On the basis of clarifying the basic principle of the ultra radiation optical refrigeration, the advantages of the double pulse pump mechanism are compared with that of the continuous pulse pump mechanism. The analytic solution of the density matrix element is derived from the kinetic equation of the stage system. Combining the spectral parameters of Yb~ (3+): YLiF4, Tm~ (3+), YILiF4 and Ho~ (3+): YLiF4 crystal, the ultra radiation optical refrigeration process is simulated by two kinds of pumping mechanism, and the power of ultra radiation optical refrigeration is changed with the temperature. It is suitable for the sample size of ultra radiation optical refrigeration. The effect of different pump energy levels on the performance of the system is discussed. The optimum selection basis for the pump energy level of the ultra radiant optical refrigeration is given through reasonable approximation and theoretical deduction.
【学位授予单位】：哈尔滨工程大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TN249

【相似文献】