基于脉冲泵浦的固体激光制冷研究

Research on Solid-State Laser Refrigeration Based on Pulsed Pumping

摘要: 固体激光制冷因其具有静音、无污染和微型化等优点，在光电探测器制冷、传感器制冷和空间飞行器冷却等领域中有着广阔的应用前景。本文将讨论以脉冲光作为泵浦源来进行固体激光制冷。我们以掺Yb³⁺氟化物晶体(Yb³⁺:YLiF₄)为例，基于密度矩阵，进一步建立更精确的四能级模型，系统分析脉冲泵浦下的动力学，给出制冷系统的优化激发方案。通过简化二能级模型解析求解出激发态粒子数极值对应的最优泵浦持续时间，并与四能级模型的数值解作误差比较。结合共振吸收截面和背景吸收截面与温度的变化关系，并带入制冷效率公式，最后模拟了制冷功率密度和制冷效率随脉冲持续时间和温度的变化关系。

Abstract: Solid-state laser cooling, with its advantages of being silent, pollution-free, and miniaturized, holds broad application prospects in fields such as photodetector cooling, sensor cooling, and spacecraft cooling. This paper discusses solid-state laser cooling using pulsed light as the pump source. Taking Yb³⁺-doped fluoride crystal (Yb³⁺:YLiF₄) as an example, we further establish a more precise four-level model based on the density matrix, systematically analyze the dynamics under pulsed pumping, and propose an optimized excitation scheme for the cooling system. By simplifying the two-level model, we analytically determine the optimal pump duration corresponding to the extremum of excited-state particle numbers and compare it with the numerical solution of the four-level model. Combining the variation relationships of resonance absorption cross-section and background absorption cross-section with temperature, we incorporate them into the cooling efficiency formula. Finally, we simulate the variation relationships of cooling power density and cooling efficiency with pulse duration and temperature.