Ph.D. Thesis
Ph.D. Thesis
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DOI：
10.1088/0004-637x/766/2/114
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
Nir S. Kampel
中科院分区：
文献类型：
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作者：
Nir S. Kampel
在本论文中，描述了处理光散射不同方面的两个不同项目。首先，我们正在研究瑞利超辐射中所体现的后向散射的起源。在这里，我们研究了探针失谐符号的起始依赖性。在第二个项目中，我们以记忆实验的形式研究了相干前向散射。在这样的实验中，我们将输入光脉冲转换为原子激发，并在稍后将原子激发转换回检索到的光脉冲。在第一个项目中，我们研究了瑞利超辐射开始时失谐符号差异的来源。当使用铷 87 中的 D1 线时，我们发现红色和蓝色失谐之间的差异高达三倍。我们通过在超辐射率的速率方程描述中添加失谐相关损耗项来对此进行建模。通过对光辅助碰撞和辐射捕获造成的损失项的微观描述，我们发现模型和实验之间存在合理的定量一致性。在第二个项目中，我们在磁阱中的超冷热样品中实现了非共振拉曼存储器，总效率为15%。此外，我们还使用平衡零差成像的检测系统对检索到的信号进行成像，该系统可以区分 30 种独立模式。本论文提出的存储器实验的目标是利用超冷样品的高光学深度实现多模存储器的第一步。在这里，我们发现，由于地平面的磁相移，相干时间为 7μs，并且当我们增加光学深度或驱动光功率时，总效率会降低，这与我们对总效率饱和的预期相反。
In this thesis two different projects are described dealing with different aspects of light scattering. In the first we are examining the origin of backward scattering as manifest in Rayleigh superradiance. Here we have studied the onset dependence on the sign of the probe detuning. In the second project, we have studied coherent forward scattering in the form of a memory experiment. In such an experiment we convert the input light pulse to an atomic excitation, and at a later time convert back the atomic excitation into the retrieved light pulse. In the first project, we investigate the source for the detuning sign difference in the onset of Rayleigh superradiance. We find a difference of up to a factor of three between red and blue detuning when using the D1 line in Rubidium 87. We model this by adding a detuning dependent loss term to a rate equation description of the superradiance. With a microscopic description of the loss term due to light assisted collisions followed by radiation trapping, we find a reasonable quantiative agreement between model and experiment. In the second project we have realized off resonance Raman memory in an ultracold thermal sample in a magnetic trap, with total efficiency of 15%. In addition we have imaged the retrieved signal using a detection system that can distinguish between 30 independent modes, using balanced homodyne imaging. The goal with the memory experiment, as presented in this thesis, is a first step towards multimode memory utilizing the high optical depth of the ultra-cold sample. Here we find that due to magnetic dephasing of the ground levels the coherence time is 7μs, and that as we increase the optical depth or the drive light power we get a reduction of the total efficiency contrary to our expectations of saturating the total efficiency.