倒Y型四能级系统中吸收谱线的窄化极限研究  

Narrowing the absorption linewidth and its limitation in a four-level inverted-Y atomic system

作　　者：邸凤清 贾宁 钱静[1] Di Feng-Qing;Jia Ning;Qian Jing(School of Physics and Electronic Science,East China Normal University,Shanghai 200241,China;Public Experiment Center,University of Shanghai for Science and Technology,Shanghai 200093,China)

机构地区：[1]华东师范大学物理与电子科学学院,上海200241 [2]上海理工大学公共实验中心,上海200093

出　　处：《物理学报》2022年第19期92-102,共11页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:12174106,11474094,12104308)资助的课题。

摘　　要：基于倒Y型四能级系统,理论研究了探测光吸收谱线的线宽窄化极限.发现得益于中间激发态与另一超精细基态之间施加的第三束控制光,线宽窄化极限的限制条件转变为两个基态能级之间的相干衰减率,而非基态与高激发态之间.与传统的梯型结构相比,吸收光谱线宽的窄化极限能够提高2个数量级.研究表明,通过适当调节这束控制光的拉比频率和失谐量,可以获得兼具超窄线宽和高对比度的吸收光谱信号.数值计算结果与理论分析完全相符.此外,还讨论了吸收谱线对光场的响应规律和多普勒效应的影响.对原子热运动的研究发现,倒Y模型由于缺少三光子作用的过程而无法完全消除多普勒增宽的影响.借助传播光场的优化设计可以减小多普勒效应的影响,在有限温度下获得较窄的吸收谱线.本文的研究成果对高分辨光谱学的实验发展具有重要的指导意义.Depending on a four-level inverted-Y atomic system,we demonstrate the limitation of linewidth-narrowing for the probe absorption spectrum in the electromagnetic induced absorption platform.Thanks to the use of an auxiliary control field which couples one hyper fine ground state and one middle-excited state we show that the linewidth limitation can be constrained by a coherence decay rate between two hyperfine ground states,rather than by the decay rate between the ground and the excited states as in previous Ladder schemes.That fact makes the theoretically-predicted absorption linewidth at least two orders of magnitude narrower.By using a suitable adjustment for the control-field amplitude and the detuning we numerically show that an extremelynarrowed probe absorption spectrum accompanied by a higher spectra contrast can be obtained,which confirms well with our theoretical predictions.We study the transient time response to the absorption spectrum and show that a relatively longer response time arises due to the small coherence decay rate between two hyperfine ground states.Furthermore,we reduce the influence on linewidth-narr owing from the Doppler effect via an optimized design of lasers,and reveal that no Doppler-free effect exists due to the lack of three-photon process.Our results may pave a route to the development of high-resolution spectroscopy in current experiments.

关 键 词：谱线线宽 倒Y型原子系统 相干衰减率 多普勒增宽 

分 类 号：O562.3[理学—原子与分子物理]