Dynamically enhanced Autler–Townes splitting by orthogonal XUV fields

Based on numerical solutions of the time-dependent Schr ¨odinger equation, we theoretically investigate the photoelectron spectrum of hydrogen atoms ionized by a pair of ultrashort, intense, and orthogonally polarized laser pulses with a relative time delay in a pump–probe configuration. The pump pulse resonantly excites electrons from the 1s and 2p levels,inducing Rabi oscillations. The resulting dynamically enhanced Autler–Townes(AT) splitting is observed in the photoelectron energy spectrum upon interaction with the second probe pulse. In contrast to the previous parallel-polarization scheme, the proposed orthogonal-polarization configuration enables the resolution of dynamically enhanced AT splitting over a considerably wider range of probe photon energies.

四波混频Autler-Townes分裂中的探测光影响

在双Λ-型四波混频系统中,研究了探测光强度对Autler-Townes(AT)分裂效应的影响.随着弱探测光强度增大,由缀饰态共振产生的AT分裂双峰间隔不变,但却逐渐增宽线宽且减弱直至消失;而在强耦合光失谐条件下,不对称地位于单光子共振峰两侧的AT分裂双峰却会逐渐趋于对称分布.详细讨论了探测光场对原子的缀饰影响,提出通过探测光强度可以调控原子两基态之间的有效Raman相干,从而影响AT分裂双峰的特征.

钾原子4p能级Autler-Townes分裂的相干控制

用缀饰态理论研究了延迟双脉冲作用下钾原子4p能级的粒子布局特征,得出缀饰态粒子布局几率与脉冲强度、延迟时间之间的关系,进而讨论当第一个脉冲面积为0.5π时,脉冲间延迟时间与4p能级Autler-Townes分裂的关系.选择合适的延迟时间可实现粒子在4p能级缀饰态的选择布局,从而控制Autler-Townes分裂.

对Autler-Townes双峰谱表达式的修正

采用了考虑反旋项的V-型三能级双共振结构模型,分别从理论推导和计算机模拟两个方面,分析了计算过程中不同因子项所起的作用.通过对各级次项适当地进行取舍,得出了修正后的简洁准确描述Autler-Townes双峰谱的表达式.

Influence of Femtosecond Laser Parameters on Autler-Townes Splitting of Three-Level Ladder Molecules

We theoretically investigate the Autler-Townes （AT） splitting in the photoelectron spectra of three-level ladder K2 molecule driven by a pump-probe pulse via employing the time- dependent wave packet approach. The dependence of AT splitting on two laser intensities and wavelengths are studied in detail. We firstly quantify these effects on peak shift and AT separation. The photoelectron spectra show double splitting with symmetric profiles, but with asymmetric profiles when the wavelength is changed. The magnitude of AT splitting increases with the pump laser intensity, but does not vary with probe intensity. The shifts of the absorption peaks and the splitting between AT doublet are predicted by using an analyt- ical fitting function when the intensity/wavelength of one of the two fields is changed. These novel results are of importance for the molecular spectroscopy and may further stimulate the first principles theoretical studies analytically.

超冷铯Rydberg原子的Autler-Townes分裂

主要研究超冷铯Rydberg原子阶梯型三能级系统的Autler-Townes(A-T)分裂.铯原子基态6S_(1/2)、第一激发态6P_(3/2)和Rydberg态形成阶梯型三能级系统,强耦合光共振作用于6P_(3/2)(F′=5)→34D_(5/2)的跃迁,探测光由偏振光谱锁定在6S_(1/2)(F=4)→6P_(3/2)(F′=5)的跃迁,并由双通的声光调制器在其共振跃迁附近扫描,形成的Rydberg原子A-T分裂谱由单光子计数器探测.A-T光谱的双峰间距与耦合光的拉比频率成正比,实验结果与理论计算在耦合光拉比频率Ω_c<2π×9 MHz时符合得很好,在拉比频率Ω_c>2π×9 MHz时,测量的A-T分裂比理论计算值小13%.产生偏差的主要原因是由于较大的耦合光拉比频率Ω_c增加了激发的Rydberg原子数,Rydberg原子间的相互作用产生了较大的退相干率所致.

Li_2 Autler-Townes分裂的实验观察(英文)

用光学 光学双共振激光光谱研究了 7Li2 A1Σ+ u 态的Autler Townes (A T)分裂 .一个强的耦合场 (泵浦激光 )激发 7Li2 A1Σ+ u v′ ,J′←X1Σ+ g v″,J″跃迁 ,诱发A1Σ+ u v′ ,J′能级和X1Σ+ g v″ ,J″能级的A T分裂 .另一个探测激光从A1Σ+ u v′ ,J′能级进一步激发到 4 1Σ+ g 态 .扫描探测激光 ,监测 4 1Σ+ g 态碰撞诱导紫色荧光 ,从而探测A1Σ+ u v′,J′能级的A T分裂 .当耦合场频率偏离共振时 ,激发光谱线出现双重分裂 .在该实验条件下 ,分裂大小和泵浦激光频率偏离共振频率的失谐量成正比 .研究了A T分裂的两条线的相对强度与泵浦、探测光的强度及缓冲气体压力的关系 .

Autler-Townes splitting in photoelectron spectra of K_2 molecule

We investigate Autler-Townes splitting in the photoelectron spectra of K2 molecule driven by pump-probe pulses via employing the time-dependent wave packet approach. It is found that the magnitude of Aulter-Townes splitting varies with the wavelength of the intense laser pulse. In particular, the phenomenon of Aulter-Townes splitting vanishes for the far-off resonance of the pump pulse. Also, the split peaks of Autler Townes in the case of resonant pump pulse give us an approach to directly obtaining the transition dipole moment of a molecule.

Relationship between electromagnetically-induced transparency and Autler–Townes splitting in a Doppler-broadened system

We study the relationship between electromagnetically-induced transparency（EIT） and Autler–Townes（AT） splitting in a cascade three-level Doppler-broadened system. By comparing the absorption spectrum with the fluorescence excitation spectrum, it is found that for a Doppler-broadened system, EIT resonance cannot be explained as the result of quantum interference, unlike the case of a homogeneously broadened system. Instead, the macroscopic polarization interference plays an important role in determining the spectra of EIT and AT splitting, which can be explained within the same framework when being detected by the absorption spectra.

Effect of pump-1 laser on Autler Townes splitting in photoelectron spectrum of K_2 molecule

We theoretically investigate the Autler–Townes（AT） splitting in the photoelectron spectrum of four-level ladder K2 molecule driven by a pump 1-pump 2-probe pulse via employing the time-dependent wave packet approach. The effects of the pump-1 laser intensity and wavelength on AT splitting are studied for the first time. The magnitude of AT splitting increases with increasing the pump-1 laser intensity. The triple splitting with asymmetric profile occurs due to the nonresonant excitation. The triple structure is transformed into a double structure（near-resonant region）, and then becomes a peak（far-off resonant region） progressively as the pump-1 laser is detuned from the resonance wavelength, which can be explained in terms of the asymmetric excitation/population of dressed states. The splitting between adjacent peaks and the splitting between the two sideband peaks in the triplet do not change with the pump-1 pulse wavelength. The three peaks shift toward lower energy with the same shift 1/4^＊△1 as the pump-1 wavelength changes in near-resonant region.The asymptotic behaviors of AT splitting with the pump-1 laser intensity are interesting in the threshold points of the near-resonant region and the far-off resonant region.

Autler-Townes doublet in the absorption spectra for the transition between excited states of cold cesium atoms

Autler-Townes splitting in absorption spectra of the excited states 6^ 2P3/2 - 8^2S1/2 Of cold cesium atoms confined in a magneto-optical trap has been observed. Experimental data of the Autler-Townes splitting fit well to the dressedatom theory, by which the fact of the cold atoms dressed by cooling/trapping laser beams is revealed. The results of the theoretical fitting with experiment not only told us the effective Rabi frequency cold atoms experienced, but also could be used for measuring the probability amplitudes of the dressed states.

Autler–Townes spectroscopy of high-lying state by phase conjugate six-wave mixing

An Autler-Townes（AT） spectroscopy based on phase conjugate six-wave mixing（SWM） is proposed to detect AT doublet of high-lying state in a Doppler-broadened cascade four-level system.It is found that the SWM spectrum is dependent strongly on the ratios between the magnitudes of the wave vectors.We discuss how the Doppler broadening affects the SWM spectrum from a time-domain viewpoint and find that,due the atomic motion,the atomic polarizations acquire different phases for atoms with different velocities as time evolves.The Doppler free SWM spectrum can be obtained only when the atomic polarization can be rephasing again at certain time after the interactions of all the incident fields.

Autler-Townes doublet in novel sub-Doppler spectra with caesium vapour cell

With a coupling laser locked to caesium 6S1/2 Fg=4-6P3/2 Fe=5 cycling transition and a co-propagating probe laser scanned across 6S1/2 Fg=4-6Pa/2 Fe=3, 4 and 5 transitions, a novel scheme for sub-Doppler spectra in Dopplerbroadened V-type three-level system is demonstrated by detecting the transmission of the coupling laser through a caesium vapour cell. The Autler-Townes doublet in the sub-Doppler spectra of the coupling laser is clearly observed. The effects of coupling laser intensity on the splitting and linewidth of the Autler-Townes doublet are experimentally investigated and the results agree well with theoretical predictions. Taking the multiple hyperfine levels of caesium atom into account, a brief analysis is presented.

Rydberg electromagnetically induced transparency and Autler–Townes splitting in a weak radio-frequency electric field

We utilize an electromagnetically induced transparency(EIT) of a three-level cascade system involving Rydberg state in a room-temperature cell, formed with a cesium 6 S_(1/2)–6 P_(3/2)–66 S_(1/2) scheme, to investigate the Autler–Townes(AT)splitting resulting from a 15.21-GHz radio-frequency(RF) field that couples the |66 S_(1/2) → |65 P_(1/2) Rydberg transition.The radio-frequency electric field induced AT splitting, γAT, is defined as the peak-to-peak distance of an EIT-AT spectrum.The dependence of AT splitting γAT on the probe and coupling Rabi frequency, ?_p and ?_c, is investigated. It is found that the EIT-AT splitting strongly depends on the EIT linewidth that is related to the probe and coupling Rabi frequency in a weak RF-field regime. Using a narrow linewidth EIT spectrum would decrease the uncertainty of the RF field measurements.This work provides new experimental evidence for the theoretical framework in [J. Appl. Phys. 121, 233106(2017)].

Crossover between electromagnetically induced transparency and Autler–Townes splitting with dispersion

Based on Akaike＇s information criterion（AIC） for a coherently driven ensemble of cold rubidium atoms, we study the crossover between electromagnetically induced transparency（EIT） and Autler–Townes（AT） splitting from the dispersion as well as the absorption viewpoint. We find that the dispersion signal is more sensitive than the absorption signal, showing more pronounced features in the Akaike per-point weights spectrum, which provides a cleaner way of discerning EIT from AT splitting.

The difference in noise property between the Autler-Townes splitting medium and the electromagnetically induced transparent medium

The quantum noise of squeezed probe light passing through an atomic system with different electromagnetically induced transparency and AutlewTownes splitting effects is investigated theoretically. It is found that the optimal squeezing preservation of the outgoing probe beam occurs in the strong-coupling-field regime rather than in the weak- coupling-field regime. In the weak-coupling-field regime, which was recently recognized as the electromagnetically induced transparency regime （Abi-Salloum T Y 2010 Phys. Rev. A 81 053836）, the output amplitude noise is affected mainly by the atomic noise originating from the random decay process of atoms. While in the strong-coupling-field regime, defined as the Autler-Townes splitting regime, the output amplitude noise is affected mainly by the phase-to- amplitude conversion noise. This is useful in improving the quality of the experiment for efficient quantum memory, and hence has an application in quantum information processing.

K_2分子Autler-Townes分裂的理论研究

利用三态模型和含时波包法,研究了三态阶跃型K2分子在泵浦—探测激光场中场强、波长对光电子能谱Autler-Townes(AT)分裂的影响.首次量化了AT分裂的峰移和间距.共振时光电子能谱为对称双峰,失谐时为不对称双峰.AT分裂间距随泵浦场强增强而增大,但不随探测场强改变而改变.AT分裂间距因泵浦波长不同而不等,但不因探测波长不同而改变.随着泵浦波长偏离共振,光电子能谱逐渐由双峰变为单峰.

单缀饰四波混频Autler-Townes分裂的分析

主要研究了单缀饰四波混频Autler-Townes分裂的相干控制。首先通过扫描探测场失谐的方式获得单缀饰四波混频信号的一阶Autler-Townes分裂;紧接着研究了一阶Autler-Townes分裂位置和宽度与缀饰场功率和失谐的定量关系。研究发现在缀饰场大失谐处,一阶Autler-Townes分裂的宽度随缀饰场功率呈现非线性变化过程,而当缀饰场位于共振频率附近则表现为线性过程。研究表明,通过选择缀饰场功率和失谐可实现对一阶Autler-Townes分裂位置和宽度的灵活控制。

多普勒加宽非匹配Λ型能级系统的无反转增益效应

对Λ型能级系统连续波无反转增益效应的研究表明 ,在耦合光的拉比频率小于多普勒宽度的情况下 ,多普勒加宽的非匹配能级系统 (耦合光波长λc 小于探测光波长λp)的无反转增益不仅存在 ,而且还强于匹配系统 (λc=λp)的无反转增益 ,文中从与无反转增益紧密联系的电磁感应透明 (EIT)

基于里德堡原子天线的短波信号接收技术

短波信号可通过电离层反射实现天波传播,传输时无需通信中继站,具有通信距离远、通信建立迅速、机动灵活、组网容易等优势,因此成为军事通信、应急通信等应用的重要方式。但由于电子学物理机理限制,传统短波天线存在尺寸大、对场地要求高、系统成本高等缺陷。基于里德堡原子天线的短波信号接收技术突破了传统短波天线的物理尺寸限制,具有尺寸小、灵敏度高等诸多优势。本文利用里德堡原子电磁感知系统进行了短波信号接收能力验证,通过对所得的EIT光谱进行转换,进而解调得到短波信号所携带信息,实现了15MHz信号接收,验证了系统短波信号接收能力。文章成果可为里德堡原子电磁感知系统短波通信应用提供技术支撑。