Tm3+掺杂玻璃激光致冷新方案的理论分析

提出了一种用于块状Tm3 掺杂玻璃ZBLANP(ZrF4-BaF2-LaF3-NaF-PbF2)激光致冷的新方案,即通过两组相互垂直的高反射率平面镜的多次反射,增加对抽运光的吸收,为了减少抽运光在样品表面入射时的反射损失,抽运光以布儒斯特角入射。重点就该方案的样品致冷温度和时间常量进行了详细的理论计算与分析,从理论上分析了入射激光功率为1 W时致冷功率和反射次数的关系,研究了不同入射激光功率下致冷温度和反射次数的关系。结果表明,入射激光功率分别为3 W、4 W5、W时,样品可以分别从室温(300 K)被冷却到275.7 K、267.4 K、259.1 K。特别是在入射激光功率为4.5 W时,样品从室温开始被冷却到263.2 K,即致冷后样品的温度下降了36.8K,比传统致冷方法提高了约53.3%,相应的致冷时间常量为22.7 min。

Theoretical Analysis on New Scheme to Cool Tm3+ -Doped Glass Sample

A) new scheme to realize laser cooling of blocky Tm~(3 )-doped glass ZBLANP(ZrF_4-BaF_2-LaF_3-NaF-PbF_2) is proposed.In this scheme,the absorption of pumping laser power is greatly enhanced by multiple reflections between two sets of mirrors with high reflectance,and with the incident angle of the pumping laser being Brewster angle,the reflection losses on the two end-faces of the sample are reduced to nearly zero.The cooling temperature of the bulk sample and its cooling time constant in this scheme are calculated in detail,and the relationship between cooling power and number of passes with 1 W incident laser power and between sample temperature and number of passes under the different incident laser power is studied.It is found that the sample is cooled from ambient temperature(300 K) to 275.7 K,267.4 K and 259.1 K when the incident laser power are 3 W,4 W and 5 W respectively.Especially,when the incident laser power is 4.5 W,the sample temperature is reduced to 263.2 K,namely,the sample temperature change is 36.8 K,which is 1.53 times of that froma conventional scheme,and the corresponding cooling time constant is about 22.7 min.