梯形三能级原子在驻波场中的偶极力分析 Alternative Title Analysis of the Dipole Force Received by a Ladder-Type Three-Level Atom in Standing Wave 王月明 Thesis Advisor 汪志诚 2005-05-20 Degree Grantor 兰州大学 Place of Conferral 兰州 Degree Name 硕士 Keyword 偶极力 主方程 三能级 驻波 涨落 Abstract 本文从原子的主方程出发应用光学布洛赫方程的方法来推导原子在激光场中所受偶极力的稳态解。首先我们推导了单色驻波场中近似等间距梯形三能级原子（ES）所受的偶极力并用数值计算作图的方法显示了偶极力及原子布居随失谐量和空间的变化。我们看到原子激发态的布居随失谐量的减小，光场强度的增加而变大，我们也观察到了跃迁饱和现象；最高能级布居在发生双光子共振时达到极大值，中间能级布居在双光子共振和单光子共振附近各出现一个极大值。可以看到偶极力主要以正弦形式振荡为主，在各波节处均为零，在波节内也会出现零点，那是因为偶极力两个分量相抵消的结果。 然后我们推导了非等间距(NES)梯形三能级原子在双色驻波场中所受到的偶极力，通过选择合适的参数我们得到了在几十个波长的空间范围内符号保持不变的的整流偶极力，并且力的大小也相当可观（相对耗散力的饱和值），从而可以为中性原子提供深势阱，这在原子的冷却，捕获和操纵上有极其重要的应用；最后我们用量子回归定理分析了所得整流偶极力的涨落，我们发现偶极力的涨落与力的大小成比例，并且可以看到归一化的扩散系数在数量级上是很小的。 Other Abstract Here we mainly derived the dipole force’s steady expressions using Optical Bloch Equations from atomic master equation. First we got the dipole force of a ladder-type three-level atom of nearly equispaced energy level at rest in a standing-wave field and showed graphically how the force and the population develop as the detuning and the space. We can see the population of the excited states becomes greater with the decrease of the detuning and the increase of the laser’s intensity. The population of the up-most level attains its maximum in the neighborhood of the two-photon resonance and the intermediate-level reaches its maximum both in the vicinity of the two-photon resonance and the one-photon resonance .The dipole force mainly varies as the sign function and becomes zero at each beat. The zero point’s occurrence of the dipole force in one beat is due to the counteract of the two component of the force . Then we derived the dipole force of a still ladder-type three-level atom of nonequispaced energy level in two standing waves of different frequencies and obtained a unidirectional rectified-force of values much greater than the dissipative force’s saturation value over tens of optical wavelength scales when the parameters are appropriately chosen,which can be used to supply a deep potential well for a neutral atom and be of great use in atom’s cooling, trapping and controlling. At last we tried to analyze the fluctuation of the rectified force using the quantum aggression theory. We find the fluctuation of the rectified-force is proportional to the force’s value and normalized fluctuation is of very small magnitude order. URL 查看原文 Language 中文 Document Type 学位论文 Identifier https://ir.lzu.edu.cn/handle/262010/229293 Collection 物理科学与技术学院 Recommended CitationGB/T 7714 王月明. 梯形三能级原子在驻波场中的偶极力分析[D]. 兰州. 兰州大学,2005.
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