1.College of Physics and Electronic Science, Hubei Normal University, Huangshi 435002, China 2.Hubei Key Laboratory of Optoelectronic Technology and Materials, Hubei Normal University, Huangshi 435002, China
Fund Project:Project supported by the Program for Innovative Teams of Outstanding Young and Middle-aged Researchers in the Higher Education Institutions of Hubei Province, China (Grant No. T2020014) and the National Natural Science Foundation of China (Grant No. 11874251)
Received Date:08 December 2020
Accepted Date:18 January 2021
Available Online:22 May 2021
Published Online:05 June 2021
Abstract:In this paper, we study the interaction of a giant ladder type four-level Rydberg atomic system with a weak light field and two strong control fields separately. We use the Monte Carlo method to calculate the dynamic evolution of this system and investigate the influence of dipole-dipole interaction on the transmission spectrum and second-order intensity correlation function of the weak probe field. By changing the value of detuning $\delta_e$ and $\delta_r$, we can obtain the asymmetric transmission spectrum of the four-level Rydberg atomic system. The influence of Doppler effect on transmission spectrum and second-order intensity correlation function are also studied. By using super atom model, the influences of different incident probe field intensities on the transmission spectrum and the second-order intensity correlation function of probe field are discussed in the Rydberg atomic system. The results show that the transmission spectrum of the four-level Rydberg atomic system is symmetric when the detuning $\delta_e=\delta_r=0$. We obtain the asymmetric transmission spectrum of the system when the value of detuning $(\delta_e, \delta_r)$ changes from 0 to 43 MHz. In order to evaluate the influence of temperature on the transmission spectrum of the system, the Lorentz distribution function is introduced to calculate the polarizability analytically. And, the influence of temperature on the asymmetric transmission spectrum and the second-order intensity correlation function are discussed at finite temperature separately. The results show that the transmittance of the outgoing probe field at the transparent window decreases with the increase of the intensity of the incident probe light field under the condition of electromagnetically induced transparency. When the intensity of the incident probe field is constant, the asymmetric transmission spectrum can be obtained by changing the detuning of the strong field. In addition, when the propagation direction of the probe field is consistent with that of the strong field, the peak value of the transmission spectrum and the peak value of the second-order intensity correlation function of the system slightly increase as the temperature increases. When the propagation direction of the detection field is inconsistent with that of the strong field, the influence of the Doppler effect on the transmission spectrum and the second-order intensity correlation function of the system can be ignored. Keywords:Rydberg atom/ Doppler effect/ asymmetry/ dipole-dipole interaction
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2.理论模型考虑图1所示的巨梯型四能级原子系统[39], 由基态$ |g\rangle $, 亚激发态$ |k\rangle $, 激发态$ |e\rangle $和一个里德伯态$ |r\rangle $组成. 一个频率为$ \omega_{\rm p} $的探测场驱动跃迁$ |g\rangle $到$ |k\rangle $, 其拉比频率为$ \widehat{\varOmega}_{\rm p}(r) = \widehat{E}_{\rm p}(r) \mu_{g k} \sqrt{\omega_{\rm p} / (2 \hbar \varepsilon_{0}V) } $; 而两个频率为$ {\varOmega_{\rm c1}} $和$ {\varOmega_{\rm c2}} $的控制场分别驱动跃迁$ |k\rangle $到$ |e\rangle $和$ |e\rangle $到$ |r\rangle $, 对应的拉比频率分别为${\varOmega_{\rm c1}} = $$ E_{\rm c 1} \mu_{k e} / (2 \hbar)$和$ {\varOmega_{\rm c2}} = E_{\rm c2} \mu_{er} /( 2 \hbar) $. 其中$ E_{\rm c1} $和$ E_{\rm c2} $分别描述第一个控制场的振幅和第二个控制场的振幅, $\mu_{xy\;(xy = g,\; k,\; e,\; r)}$表示$ |x\rangle\rightarrow|y\rangle $跃迁的电偶极矩, $ \widehat{E}_{\rm p}(r) $表示探测场的振幅算符, V表示里德伯原子的量子探测体积, 考虑偶极-偶极相互作用, 系统的哈密顿量可以表示为 图 1 里德伯原子系统能级示意图, 一个失谐量为$ \delta_{\rm p} $的弱探测场驱动基态到亚激发态的跃迁, 第一个失谐量为$ \delta_e $的强控制场驱动亚激发态到激发态的跃迁, 第二个失谐量为$ \delta_r $的强控制场驱动激发态到里德伯态的跃迁. 实际能级基于铯原子选取 Figure1. General energy level diagram for four levels Rydberg atomic system. A weak probe field, detuned from the intermediate level by $ \delta_{\rm p} $, drives transitions from the ground state $ |g\rangle $ to the intermediate state $ |k\rangle $. The first strong control field, detuned from the intermediate level by $ \delta_e $, drives transitions from the intermediate state $ |k\rangle $ to the excited state $ |e\rangle $. State $ |r\rangle $ is a Rydberg state directly coupled to state $ |e\rangle $ by the second strong control field $ {\varOmega_{\rm c2}} $. Real energy levels are shown based on Cs atoms.
$ \widehat{H} = \widehat{H}_{\rm a}+\widehat{V}_{\rm a f}+\widehat{H}_{\rm v d w}, $