-
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 hyperfine 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 extremely-narrowed 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-narrowing 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.
-
Keywords:
- spectrum linewidth /
- inverted-Y type atomic system /
- coherence decay rate /
- Doppler broadening








下载: