原子在两个平行镜面间两层电介质板中的自发辐射率

利用光子的闭合轨道理论,我们研究了原子在两个平行镜面间两层电介质板（折射率分别为n1,n2）中的自发辐射率. 自发辐射率呈现出多周期的振荡结构。自发辐射率的傅立叶变换中的每一个峰和光子从原子出发到返回原子的一条闭合轨道相对应。结果表明自发辐射率和两层电介质的宽度和折射率有关。和只有一层电介质的辐射率比较,当两层电介质的折射率n1 和 n2 差别很小时, 两层电介质之间分界面的反射效应可以忽略;但是当二者的差别很大时,发射效应变得非常重要且自发辐射率中的振荡减弱。本文的结果为原子在不同电介质间的自发辐射率的研究提供了新的理解。     

Calculations of spontaneous emission rates of a single-impurity molecule in uniaxial host crystals

In a uniaxial host crystal the spontaneous emission rate of the dipole transition of the zero-phonon line of a single-impurity molecule depends on the angle between the transition dipole moment and the optical axis of a crystal and as well as on the ordinary and extraordinary refractive indices. The relative spontaneous emission rate (the spontaneous emission rate divided by the spontaneous emission rate in the case when the transition dipole moment is parallel to the optical axis) is determined through a simple formula by one coefficient. Here this coefficient is calculated as a function of the extraordinary refractive index for 40 values of the ordinary refractive index on the interval from 1.25 to 3.20. For comparison, the effects caused by the nearness to the plane interface between cinnabar crystal (HgS) and air, as an example, are calculated.     

Spontaneous emission of two interacting atoms near an interface

The spontaneous emission rate of two interacting excited atoms near a dielectric interface is studied using the photon closed-orbit theory and the dipole image method. The total emission rate of one atom during the emission process is calculated as a function of the distance between the atom and the interface. The results suggest that the spontaneous emission rate depends not only on the atomic-interface distances, but also on the orientation of the two atomic dipoles and the initial distance between the two atoms. The oscillation in the spontaneous emission rate is caused by the interference between the outgoing electromagnetic wave emitted from one atom and other waves arriving at this atom after traveling along various classical orbits. Each peak in the Fourier transformed spontaneous emission rate corresponds with one action of photon classical orbit.     

Fluorescence spectrum due to surface plasmon polariton emission in a three level atom

The dynamics of a V-type three level atom positioned inside a metallic slab sandwiched between two asymmetric infinite dielectrics is studied. The surface plasmon polaritons supported by this structure are calculated, quantized and their dispersions are found to exhibit plasmonic band gaps which in turn modify the spontaneous transition rates and the fluorescence spectrum. Interesting features arise from the variations of the decay rate and spectrum with the mode frequency and electron density including local field effects.     

Extracting Oscillation Frequencies in Spontaneous Emission Rate of an Atom Between Two Mirrors

For an atom in a medium with refractive index n sandwiched between two parallel mirrors, we derive an analytical formula for the spontaneous emission rate based on Fermi＇s golden rule. The oscillations are not transparent in this formula. By performing Fourier transform on scaling variable measuring system size while holding system configuration fixed, we extracted the frequencies of many oscillations in this system. We show that these oscillations correspond to emitted photon closed-orblts going away from and returning to the emitting atom.     

介质腔中自发辐射原子的寿命分布

在本文中,我们研究了半无限大介质板夹层对空腔中激发态原子的自发辐射率的影响,并利用寿命分布函数来描述原子衰变动力学的性质,在对称和非对称的结构中,分别计算了以原子在板中的相对位置为自变量的原子自发辐射率的函数,计算结果表明,原子的自发辐射率与介质腔的宽度以及外层半无限大介质板的折射率有关,介质腔可以增强或抑制激发态原子的激发,当介质腔的宽度足够大时,原子的寿命分布呈现指数衰减的形势,这些理论结果和实验值相符合的非常好.     

Correspondence Between Oscillations and Emitted Photon Closed-Orbits in Spontaneous Emission Rate of an Atom Near a Dielectric Slab

We study the oscillations in the spontaneous emission rate of an atom near a dielectric slab. The emission rate is calculated as a function of system size using quantum electrodynamics. It exhibits multi-periodic oscillations. Four frequencies of the oscillations are extracted by Fourier transforms. They agree with actions of photon closed-orbits going away and returning to the atom. These oscillations are explained as manifestations of quantum interference effects between the emitted photon wave near the atom and the returning photon waves travelling along various closed-orbits.     

Localization and kinetics of an atom in the spectral filtration of its resonance fluorescence

It is shown that spectral filtration of a significant fraction of radiation of a resonantly fluorescing atom changes its kinetics. The effect of a spectral observation event on the behavior of an atom is demonstrated by two examples: localization of an atom at its flight through a region occupied by a standing light wave and translatory dynamics of an atom at its motion along a standing light wave. In the first case, localization probabilities are calculated in the absence of spontaneous emission events and for one photoemission event. The arising distribution over the atomic momentum, which is sensitive to spectral filtration, is also calculated for one photoemission event. In the second example, it is shown that spectral filtration of spontaneous emission leads to the occurrence of an anomalous additive to the force acting on an atom in the standing-wave field.     

Effect of Spontaneous Emission on Both Atomic Dynamics and Momentum Transfer of an Atom-cavity System

The dynamics of an atom coupling to a quantized cavity field have been studied. The atom is treated as a two-level system with a spontaneous emission rate. The transition probabilities have been given for both adiabatic and non-adiabatic situations. For a special Λ-type atom with dark state, the problem of momentum transfer is discussed in details. The influence of spontaneous emission on validity of the adiabatic approximation is also discussed.     

Effect of Spontaneous Emission on Both Atomic Dynamics and Momentum Transfer of an Atomcavity System

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Bosonic enhancement of spontaneous emission near an interface

We show how the spontaneous emission rate of an excited two-level atom placed in a trapped Bose-Einstein condensate of ground-state atoms is enhanced by bosonic stimulation. This stimulation depends on the overlap of the excited matter-wave packet with the macroscopically occupied condensate wave function, and provides a probe of the spatial coherence of the Bose gas. The effect can be used to amplify the distance-dependent decay rate of an excited atom near an interface.     

The Electromagnetically Induced Transparency of Quasi-A-type Four-level Atom System at Low Light Levels

The probe gain and the population in high level in the Quasi-A-type four-level atom system interacting with two fields at low light levels are investigated in this paper： The system always displays three gain peaks with probe detuning. At the same time, the electromagnetically induced transparency （EIT） can be observed in two windows which only relate to coupling detuning. When the system displays EIT, the population in the high level is zero. If the phase of the probe field is changed, the probe gain would be changed and absorption occurs but the population in the high level is a constant. It is worth noting that all results are got on the condition that the fields are as weak as the spontaneous emission fields and without any approximation.     

太赫兹波段微腔器件的设计及其特性研究

采用磁控溅射法制备了金属Cr膜, 并利用太赫兹时域光谱法获得了其光学参数. 利用Cr膜的光学参数计算了其相位穿透深度, 设计了基于低温GaAs 的全金属平面微腔光电导太赫兹辐射器件. 模拟结果表明: 器件的谐振频率分别为0.32, 0.65, 0.98, 1.31和1.65 THz, 与自由空间的光电导太赫兹谱相比, 在谐振频率为0.32 THz处的峰值强度提高了25倍, 光谱半高全宽压缩了50倍. 讨论了辐射偶极子与腔内驻波场之间的耦合强度对器件辐射强度的影响, 发现当辐射中心位于驻波场波腹处时, 器件辐射最强, 位于波节处时辐射被严重抑制. 太赫兹波段微腔效应的研究对于实现单色性好, 连续调谐, 高效高辐射强度的太赫兹源具有一定的理论意义.     

Anisotropy of IR Absorption of an Ultrathin Water Layer on a Water/Quartz Glass Interface

Optics and Spectroscopy - The optical properties of an ultrathin water layer at the interface between two dielectrics (ZnSe–SiO2) are studied by FTIR spectroscopy. Effective refractive...     

Spontaneous emission from Bloch states of a two-level atom in a periodic field of the biparabolic shape

By analogy with the Wigner-Weisskopf model, spontaneous emission of an atom is considered in a spatially periodic field of the resonance counter-propagating waves. The Bloch state obtained by the interaction of the initially excited (unexcited) atom with a field of the counter-propagating waves plays the role of the excited (ground) state of the free atom. The spontaneous emission probability averaged over polarizations is shown to become anisotropic, with the symmetry axis directed along the wave propagation path. The anisotropy is caused by the spatially periodic distribution of the wave function of the translational motion of an atom in the external field. The degree of anisotropy depends on the position of Bloch energy levels in the allowed bands of the energy spectrum.     

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.     

Spontaneous emission from a ladder three-level atom in anisotropic photonic crystals

We investigate the spontaneous radiation from a ladder three-level atom embedded in a three-dimensional anisotropic photonic crystal with an external driving field. The properties of the spontaneous emission are dependent strongly on the relative position of the middle level from the band edge. Due to the Autler-Townes splitting by the action of the driving field, the external driving field can also affect the properties of the spontaneous emission. The population exchanged between the upper and the middle levels decreases as the detuning of the external driving field frequency from the corresponding transition frequency increases. The properties of the emission field can be changed or so much as controlled by choosing suitable intensity of the external driving field. The emission spectrum is more complex, and dependent on the location of the observer in this case.     

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.     

Influence of dielectric microcavity on the spontaneous emission rate of atom: a perspective on the closed-orbit theory of photons

The formulas of the quantum electrodynamics have been applied to calculate the spontaneous emission rate of excited atom in dielectric microcavity.The results exhibit damping oscillating Patterns which depend sensitively on the scaling parameter and geometrical structure.Compared with the case that the emitting atom is immersed in dielectric,the spontaneous emission rate is depressed obviously and the center or the mean value of the oscillations is intimately related to the real refractive index of the local position where the atom is.In order to explain this phenomenon,we utilize the closed-orbit theory to deal with the classical trajectories of the emitted photon.and extract the corresponding frequencies of the oscillations by Fourier transform.It is found that the oscillations can be represented in terms of the closed-orbits of the photon motion constrained in dielectric microcavity,thus providing another perspective on the spontaneous emission of atom sandwiched by dielectric slabs.     

Time Quanta

Secondary quantizing of the “passive mass” of an isotropic and uniform nonstationary scalar field is realized, and the intensity of quantum emission of the massless scalar field is calculated for spontaneous transitions of the effective Planck particle in the line energy spectrum of the primordial Lema?tre atom. It is shown that the scalar-field quanta in the effective Riemann space can manifest themselves as time quanta of the real Minkowski space.