各向异性光子晶体中∧型原子的自发辐射性质

讨论了各向异性光子晶体中∧型三能级原子的辐射性质.研究发现,原子上能级与光子晶体带边的相对位置和两低能级相对位置将直接影响原子的动力学性质及其周围辐射场的性质.通过数值计算和理论分析,得到了光子晶体中原子周围辐射场在不同位置随时间演化的图像,并讨论了光子晶体对原子辐射谱的影响.     

各向异性光子晶体中Λ型原子的自发辐射性质

讨论了各向异性光子晶体中Λ型三能级原子的辐射性质. 研究发现，原子上能级与光子晶体带边的相对位置和两低能级相对位置将直接影响原子的动力学性质及其周围辐射场的性质. 通过数值计算和理论分析，得到了光子晶体中原子周围辐射场在不同位置随时间演化的图像，并讨论了光子晶体对原子辐射谱的影响.     

Yb原子奇宇称受扰里德堡系n^1P1,n^3P1能级自然辐射寿命的研究

通过激光与原子束相互作用，三步激发及时间分辨光谱术，测量了Ｙｂ原子奇宇称受扰里德堡系６ｓｎｐ＾１，３Ｐ１２１个能级和两上干扰能级的自然辐射寿命，分析了各种因素对测量值的影响。     

磁约束飞秒激光诱导铜等离子体特性研究

建立磁约束飞秒激光诱导铜等离子体辐射光谱采集系统,通过发射光谱法分析磁约束效应对飞秒激光诱导铜等离子体特性的影响.在强度为0.67T的稳磁场约束下,等离子体辐射连续谱和分立谱均有增强,分立谱线增强更显著;铜原子上能级越高,其辐射的原子谱线增强因子越大,具有最高上能级的Cu I 507.6nm增强因子最大,为2.8;等离子体铜原子谱线持续时间明显延长,在等离子体演化初期,谱线增强显著,在较大延时,谱线增强迅速减弱;等离子体电子温度和电子密度均有提高.     

原子运动对双光子JC模型能级分裂的影响

研究了双光子JC模型中原子运动对能级分裂的影响及其在原子辐射谱中的反映。结果发现,当原子具有确定的动量和光场处于Fock态时,每个原子能级具有两个值,原子辐射谱的谱线相应地分裂为两条。原子分裂能级的间隔主要依赖于原子和光子的动量的差值。     

为什么吸收光谱中的暗线比发射光谱中的明线少

如图所示,表明了原子的各个可能的能级状态.原子所辐射的或吸收的光子的能量,总等于两个能级间的能量差,因此同一原子的发射光谱中的明线和吸收光谱中的暗线有其对应性.但并不是对应所有的发射光谱中的明线都能观察到相应的吸收光谱中的暗线,其原因有四.     

铥原子中等能量能级自然辐射寿命的时间分辨荧光测量

报道铥(Tm)原子10个中等能量激发能级自然辐射寿命的实验测量值.采用两台脉冲染料激光器将铥原子从基态激发到待测能级,再从铥原子激发态所释放的荧光随时间衰变的规律推算出自然辐射寿命值.测量精确度为10％.     

光解产生的铅原子中受激喇曼散射和共振激光辐射

用2660(?)的紫外激光解离PbCl_2分子时,发现在3740(?)和3734(?)波长上有较强的受激辐射输出.根据它们的光谱特性和铅原子的能级结构判断,这些辐射是基于双光子解离PbCl_2分子得到的铅原子在6p~(23)P_2亚稳能级上的布居而产生的光泵共振激光辐射和受激喇曼散射.提出了描述整个过程的理论模型,通过拟合实验结果,确定了2660(?)激光双光子解离PbCl_2产生6p~(23)P_2亚稳态铅原子的光解系数.当PbCl_2分子密度为N_(00)=6.21×10~(16)cm~(-3)时,光解产生的铅原子在6p~(23)P_2和6p~(21)D_2这两个亚稳态的最大布居数近似相等,称为2.0×10~(16)cm~(-3).     

V型三能级原子系统中电磁诱导各向同性的二维左手效应

研究被两正交光场耦合的V型三能级原子系统中电磁诱导下的左手效应.讨论了正交耦合光场强度、探测场失谐量和上能级间自发辐射耦合相干对该原子系统介电常数、磁导率和折射系数的影响.研究表明,在合适的参数条件下,该原子系统的介电常数、磁导率在二维相同的区域内同时为负值,且取值分布具有各向同性的特征;即产生了各向同性的二维左手效应.     

各向异性光子晶体中Λ型原子动力学性质研究

讨论了各向异性光子晶体中外驱动场作用下Λ型原子的动力学性质及辐射谱特性. 通过理论 分析和数值计算发现，原子上下能级的布居数将出现准周期性振荡的性质，其振荡的频率和 振荡的幅度与上能级的耗散系数γ， 驱动场的作用强度，驱动场和共振频率失谐度δ等相 关； 原子上能级与光子晶体带边的相对位置将直接影响到原子自发辐射的模式. 此外，从 辐射谱的角度分析光子晶体对原子周围辐射场的特性及其传输性质的影响.     

INFLUENCE OF ATOMIC MOTION ON SPONTANEOUS EMISSION FROM A THREE-LEVEL ATOM

本文研究了V型三能级原子的自发辐射谱。如果不考虑原子的质心运动,则自发谱中有一暗线,这是干涉所致。如果考虑原子的质心运动,则暗线消失,即原子的质心运动破坏了干涉效应。     

压缩真空中的三能级原子的自发辐射

对压缩真空与Ｖ型三能级原子的相互作用作了理论分析,探讨了量子干涉效应对压缩真空中原子自发辐射的影响。当原子的上能级简并时强的量子干涉效应影响原子的定态和定态出射光谱,使它们对原子的初态敏感。这种情况下,压缩使谱线趋于关于压缩真空中心频率对称,量子干涉使谱线趋于不对称。     

Modified spontaneous emission spectra of a three-level V-type atom in photonic crystals

We introduce a modified density of modes to investigate the spontaneous emission spectrum of a three-level V-type atom in photonic crystal using Laplace transform. The atom’s steady state behavior of spontaneous emission is treated for different locations of the upper band-edge frequency. Furthermore; the influence of quantum interference between the two decay channels on spontaneous emission is discussed.     

Coherent control of interference processes in radiative decays

Possibility of coherent control of spontaneous emission from four- and five-level system in the laser radiation field is studied. The four-level system consists of two levels resonantly driven by laser radiation where either of levels may decay to a separate level. For such a system, we show that the presence of the second decay channel may deteriorate the destructive interference occurring in case of one decay channel because of Autler-Townes effect. The five-level diagram represents two two-level resonantly driven systems with the upper levels decaying to a common level. For this diagram, interference between the two decay channels takes place and it is partially or completely destructive or constructive depending on the initial conditions and on the mutual orientation of the transition dipole moments. It is shown that population transfer takes place by the same quantum vacuum via spontaneous emission. The populations are shown to have damping oscillatory nature.     

Spontaneous emission spectrum of a three-level atom embedded in photonic crystal

The two models of three-level (one upper level and two lower levels, or two upper levels and one lower level) atom embedded in a double-band photonic crystal are adopted. The atomic transitions from the upper levels to the lower levels are assumed to be coupled by the same reservoir which are respectively the isotropic photonic band gap (PBG) modes, the anisotropic PBG modes and the free vacuum modes. The effects of the fine structure of the atomic ground state levels in the model with one upper level and two lower levels, and the quantum interferences in the model with two upper levels and one lower level on the spontaneous emission spectrum of an atom are investigated in detail. Most interestingly, it is shown that new spontaneous emission lines are produced from the fine splitting of atomic ground state levels in the isotropic PBG case. The quantum interferences induce additional narrow spontaneous lines near the transition from the empty upper level to the lower level.     

Quantum interference effect on spontaneous emission spectrum in a doubly driven M-type atom

An M-type atomic system with two closely spaced upper levels interacting with the same modes of the vacuum radiation field exhibits the interference effect between the spontaneous decay channels. The phenomenon of this decay-interference along with the dynamically induced quantum interference created in the system by two coherent fields can change significantly the spontaneous emission spectrum. Our results highlight large enhancement of ultranarrow spectral components within the spontaneous emission line shape in various conditions. We have shown the occurrence of two contradistinctive phenomena: compression of two spectral lines towards their mid-position and the spreading of two lines away from each other under different dynamic conditions. The phenomenon of suppression of spectral line and the quenching of spontaneous emission have also been focused.     

Spontaneous emission of a three-level lambda-type atom coupled to separate reservoirs

Considering the anisotropic dispersion model, the upper state population and spontaneous emission spectrum of three-level lambda-type atom with two transitions coupled to separate reservoirs are investigated using the resolvent operator. The upper state population reaches to a steady state value after a weak oscillation when the decay rate is zero and one transition frequency is inside the bandgap. The spectrum associated with each transition was given. Compared with results that were obtained by using isotropic dispersion model, the shape of spectrum changes significantly, and no dark line appears in the spectra.     

Effect of atomic initial phase difference on spontaneous emission of an atom embedded in photonic crystal

<正>We investigate the effect of initial phase difference between the two excited states of a V-type three-level atom on its steady state behaviour of spontaneous emission.A modified density of modes is introduced to calculate the spontaneous emission spectra in photonic crystal.Spectra in free space are also shown to compare with that in photonic crystal with different relative positions of the excited levels from upper band-edge frequency.It is found that the initial phase difference plays an important role in the quantum interference property between the two decay channels.For a zero initial phase,destructive property is presented in the spectra.With the increase of initial phase difference,quantum interference between the two decay channels from upper levels to ground level turns to be constructive.Furthermore, we give an interpretation for the property of these spectra.     

Quantum interference enhancement with left-handed materials

The quantum interference between two spontaneous emission transitions, which are orthogonal, in a three-level system, can be greatly enhanced by using left-handed materials due to the focusing and phase compensation effects. The influence of the dispersion and dissipation of the materials on the quantum interference enhancement is investigated, and the enhancement of quantum interference is still significant. The quantum interference enhancement will result in a large quenching of the spontaneous emission, even if the distance between the materials and systems is larger than 10 wavelengths.     

压缩真空中的三能级原子的自发辐射强场高次谐波时间特性的理论分析

对压缩真空与V型三能级原子的相互作用作了理论分析, 探讨了量子干涉效应对压缩真空中原子自发辐射的影响。当原子的上能级简并时强的量子干涉效应影响原子的定态和定态出射光谱, 使它们对原子的初态敏感。这种情况下, 压缩使谱线趋于关于压缩真空中心频率对称, 量子干涉使谱线趋于不对称。通过用单电子近似求解含时薛定谔方程, 用加窗傅里叶分析的方法, 分析了单原子产生的高次谐波的时间特性。理论分析表明, 基态粒子数消耗对不同级次谐波辐射的影响程度不一样; 谐波辐射随着入射激光场强度的增加会出现饱和; 随着谐波级次的增加, 谐波辐射越来越趋向于集中在更短的时间间隔内, 相应的线宽也随着谐波级次的增加而增加。