【作者】 钟标；

【导师】 印建平；

【作者基本信息】 华东师范大学 ， 光学， 2014， 博士

【摘要】 固体材料激光冷却有许多有趣的物理现象,同时在航空航天、遥感遥测、光电探测、高功率激光器等领域有着广泛而重要的应用。因此,固体材料激光冷却的研究不仅有着重要的科学意义,而且有着强烈的应用背景。本文以掺杂Yb3+的氟化物晶体作为激光冷却的研究对象展开深入系统的理论和实验研究。我们采用四能级模型描述掺杂稀土离子激光冷却的物理过程,得出固体材料激光冷却的制冷效率与外部量子效率、吸收效率、平均荧光波长和泵浦激光波长的关系。样品的热负载主要有三部分组成：黑体辐射热负载、空气对流热负载和支撑物传导热负载,我们详细分析了这三种不同热负载对固体材料激光制冷的影响,并给出减小这些热负载的解决方案。微纳探测器的全固态冷却对科研工作者提出了新的挑战。本文提出了两个微纳米尺度范围探测器的全固态冷却新设想。这两个新设想是采用表面等离子体共振增强激光冷却方案和相长干涉增强激光冷却方案来实现微纳米探测器的有效冷却。我们首先推导了增强因子在薄膜中的空间分布,得到平均增强因子表达式。然后,以10wt%Yb3+:YLiF4薄膜为例,计算了不同薄膜厚度时,泵浦激光增强因子在薄膜内的空间分布。最后,计算了10wt%Yb3+:YLiF4薄膜能被激光冷却的最终温度和泵浦功率的关系。在计算时我们考虑了样品对激光的饱和吸收效应。本文采用共振腔增强吸收激光技术实验研究掺杂2wt%Yb3+:YLiF4晶体的激光冷却。首先,我们测量该晶体的平均荧光波长和温度的变化关系；接着,用DLT测温法对该晶体进行温度定标。然后,我们利用电子伺服系统,把谐振腔锁定在半导体激光上。谐振腔与入射激光共振约一小时后,我们同样采用DLT测温法测量样品光谱信号,并与原先的温度定标曲线作比较得到样品的实际温度。接下来,利用四能级模型分析实验结果,得到样品的制冷功率、制冷效率和背景吸收系数。并根据理论分析得到的实验结果,我们做出了能全面而准确反映该2wt%Yb3+:YLiF4晶体的激光制冷属性的“窗口”。最后,把我们实验结果与阿拉莫斯实验室和新墨西哥大学的实验结果做简单直接的比较。本文采用共振腔增强吸收激光技术实验探索研究掺杂2wt%Yb3+:LuLiF4晶体的激光冷却。首先,我们在理论上分析了掺杂Yb3+氟化物材料能被激光冷却至低温学温度的要求,并得出能被激光冷却到低温学温度的几种可能氟化物晶体材料。然后,我们测量该晶体的平均荧光波长和温度的变化关系；接着,用DLT测温法对该晶体进行温度定标。然后,我们利用电子伺服系统,把谐振腔锁定在半导体激光上。谐振腔与入射激光共振约一小时后,我们采用DLT测温法测量样品光谱信号,并与原先的温度定标曲线作比较得到样品的实际温度。接下来,利用四能级模型分析实验结果,得到该晶体的制冷功率、制冷效率和背景吸收系数。根据理论分析并结合实验结果,我们做出了能全面而准确反映该2wt%Yb3+:LuLiF4晶体的激光制冷属性的“窗口”。最后,我们比较了Yb3+:LuLiF4晶体和Yb3+:YLiF4晶体两者之间的制冷潜力,以及在晶体生长和实际应用方面的优缺点,并发现Yb3+:LuLiF4晶体与Yb3+:YLiF4晶体有着同样迷人的制冷前景。更多还原

【Abstract】 Laser cooling of solids is becoming more attractive for both fundamental physical scientists and applied physical scientists due to it has tremendous charming physical phenomenon and extremely important application in the area of aerospace, remote sensing and telemetry, photoelectric detection, high power laser and so on. This dissertation main study laser cooling of Yb3+-doped fluoride crystal in theory and in experiment.We adopted four energy level model describe the process of laser cooling of the rare earth doped system. According to this model, we obtained the relationship the cooling efficiency with external quantum efficiency, absorption efficiency, mean fluorescence wavelength, and pump wavelength. The heat loads of the sample come from three parts:blackbody radiative load, air convective heat load, supporting conductive heat load. We analyzed the effect of heat load from these three different sources and give the solution to reduce the heat load correspondingly.Cooling micron or nano scale detector is the new challenge for us. We propose two new conceptions which are Surface Plasmon Resonant enhancement laser cooling of solids (SPRELCS) and resonant waveguide structure coherent enhancement laser cooling of solids (RWCELCS) for cooling the micro or nano scale detectors. Firstly, we deduced the relationship the enhancement factor with the position of film and obtained the express of the mean enhancement factor. Secondly, we adopted the10wt%Yb3+:YLiF4film as our model in the theory, and calculated the enhancement factor function in the film with the different thickness of the film. Finally, we calculate relationship the final temperature of10wt%Yb3+:YLiF4film with the power of the pumping laser. While the process of the calculation, we taken account of the saturate power intensity.We adopt the resonant external cavity enhancement absorption experiment study the laser cooling of2wt%Yb3+:YLiF4crystal. Firstly, we measured the relationship the mean fluorescence wavelength with temperature. And then, we obtained the temperature calibration curve of the sample with DLT method. After that, we lock the length of the cavity on the wavelength of the pump laser. On hour later, the sample reached the state of thermal balance with environment, and then we recorded the DLT single of sample. Compared with the temperature calibration curve in early, we can deduce the final temperature of the sample. Utilizing the four energy level model, we can obtain the cooling power, cooling efficiency and background absorption. According to these results, we can draw the cooling window of2wt%Yb3+:YLiF4crystal by which we can comprehensive understanding of the properties of laser cooling of this crystal. Finally, we compared our experiment results with the results of LANL and University of New Mexico research group directly.We adopt the resonant external cavity enhancement absorption experiment study the laser cooling of2wt%Yb3+:LuLiF4crystal. Firstly, we analyzed the demands for Yb3+-doped fluoride materials cooled down to cryogenics temperature by laser in theory. And obtained some Yb3+-doped fluoride crystal as potential candidates who can be cooled down to cryogenics temperature by laser. And then, we measured the relationship the mean fluorescence wavelength with temperature. We also obtained the temperature calibration curve of the sample with DLT method. After that, we lock the length of the cavity on the wavelength of the pump laser. On hour later, the sample reached the state of thermal balance with environment, and then we recorded the DLT single of sample. Compared with the temperature calibration curve in early, we can deduce the final temperature of the sample. Utilizing the four energy level model, we can obtain the cooling power, cooling efficiency and background absorption. According to these results, we can draw the cooling window of2wt%Yb3+:LuLiF4crystal by which we can comprehensive understanding of the properties of laser cooling of this crystal. Finally, we compared the potential of cooling ability of both the Yb3+:LuLiF4crystal and the Yb3+:YLiF4crystal and the advantages for the crystal growth and the practical application between them. And we found out both of them there is the same promising potential for laser cooling to cryogenics temperature.更多还原