摘要
基于五能级结构手征原子媒质,对光学时域隐身在外场调控下的实现进行了研究。在该五能级手征原子系统下,推导了原子媒质与光场参数相关的等效电磁响应参数的广义表达式,进而根据群折射率计算输出光脉冲。数值计算了五能级原子系统的外场以及原子媒质相关参数对隐身时域窗口大小以及形成时域窗口的光脉冲强度的影响。结果表明,时域窗口大小随控制场Rabi频率改变但基本不依赖于控制场的相位变化;两个耦合场相位在一个周期内的变化对左右旋圆极化输出波特性影响相反;两个耦合场中,当其中一个耦合场的Rabi频率减小时,对应时域窗口增大,但同时也会使形成窗口的脉冲强度减弱,而另一个耦合场Rabi频率则对时域窗口的大小影响较小。因此改变控制场和两个耦合场的强度、相位和失谐等参量可有效地调控输出脉冲的加速和延迟,产生显著的隐身时域窗口,提供了一种可操控的光学时域隐身的方案。
With the advancement of optical temporal cloaking,this technology has attracted increasing attention,and the related theoretical and experimental studies were intensively carried out.Unlike spatial cloaking,which controls the path of electromagnetic wave propagation by manipulating controllable electromagnetic parameters of the medium,optical temporal cloaking does not result in light deviating from its expected spatial trajectory.Instead,the optical signals is divided into leading and trailing parts,which creates a temporal cloak window that can conceal events.Typically,two light signals are either speed up or slowed down,preventing them from reaching inside the temporal cloak window and interacting with nonemitting materials,thus rendering internal events unobservable to observers.This approach,which conceals events for a limited duration rather than the object itself,has broad application prospects in many fields.In this work,we explore the implementation of optical temporal cloaking via a chiral atomic medium with a five-level structure.By enhancing the laser control field and employing a weak probe field,coherent coupling between electric dipoles and magnetic dipoles can be induced during the transition process.Alterations to the external laser field allow for the control of magnetoelectric coupling,leading to significant chirality.Within the chosen five-level chiral atomic system,the generalized expressions in terms of the parameters related to the atomic medium and the light field are derived.Subsequently,based on the group refractive index,the output light pulse were calculated.Numerical calculations were then carried out to analyze the influence of the external field and the length of atomic medium for the five-level atomic system on the width of the temporal cloak window and the intensity of the light pulses that form the window.The results show that the input pulse generates left and right circularly polarized beams through the five-level chiral atomic medium.The intensity variation of the output pulse depends on the parameter of the external field,and the output time has different extents of advance or delay.An effective temporal window is formed within a certain parameter range.In the effective temporal window,the amplitude of the control field influences the width of the temporal window,while the phase of the control field hardly affect the window width.Furthermore,within the amplitude range of one of the two coupling fields,the temporal cloak window is nearly unaffected by that amplitude.Conversely,an increase in the amplitude of the other coupling field results in a reduction of the temporal cloak window width,while a weaker amplitude of the coupled field causes both output pulses to exhibit characteristics of speeding up.In a certain range of control field phase and coupling field phase,an effective cloaking time window can be observed,in which the optical pulse shows the opposite law to the control field phase change in the process of one of the coupling field phase change,while in the change process of the phase of the other coupling field,it shows a law similar to that of the control field phase change.As the length of the medium increases,the temporal window is gradually widened,but the intensity of the light pulse weakens due to increased loss in the medium.Therefore,it is necessary to avoid long transmission distance to ensure the effectiveness of optical temporal cloaking.Consequently,the acceleration and delay of the output pulses can be controlled effectively by manipulating the strength,phase,and detuning of the control and the coupling fields,and a significant temporal cloak window can be obtained,and this provides a tunable optical temporal cloaking scheme.
作者
方世超
曾然
徐静俏
吕晓燕
李浩珍
杨淑娜
羊亚平
FANG Shichao;ZENG Ran;XU Jingqiao;LV Xiaoyan;LI Haozhen;YANG Shuna;YANG Yaping(School of Communication Engineering,Hangzhou Dianzi University,Hangzhou 310018,China;MOE Key Laboratory of Advanced Micro‒Structured Materials,School of Physics Science and Engineering,Tongji University,Shanghai 200092,China)
出处
《光子学报》
EI
CAS
CSCD
北大核心
2024年第2期190-199,共10页
Acta Photonica Sinica
基金
浙江省自然科学基金(No.LY20A040003)
国家自然科学基金(Nos.12274326,61901148,11574068)
浙江省属高校基本科研业务费专项资金(No.GK199900299012-015)。
关键词
手征原子媒质
磁电耦合
光学时域隐身
五能级系统
量子相干
Chiral atomic medium
Magnetoelectric coupling
Optical temporal cloaking
Five-level system
Quantum coherence
