Cavity Field Spectra of a Cascade Three-Level Atom Interacting with a Single-Mode Field with Kerr-Like Medium

The cavity field spectrum of a cascade three-level atom interacting with single-mode field with Kerr-like medium in the cavity is investigated. The numerical results for the initial field in pure number state, coherent state and squeezed vacuum state are calculated, respectively. It is found that the Kerr-like medium affects the spectral structure even though the initial field is in vacuum when the atom is in upper level. In the case of strong input field, the number state spectrum shows two peaks with different heights; and the superposition state spectrum shows a multipeak structure with an equal distance of two neighboring peaks. The spectral ＂central frequency＂ shifts away from the resonant frequency with the increasing of average photon number.     

Multiscaling wavelet analysis of infrared and Raman data on polyethylene glycol 1000 aqueous solutions

Infrared and Raman scattering spectra of aqueous solutions of poly(ethylene glycol) with nominal weight 1000 Da have been collected and analyzed as a function of the water content both in terms of a two-state physical model and in terms of an innovative multiscale wavelet cross-correlation approach. Both the analysis procedures allow to highlight the spectral shape changes occurring when water is added to pure polymer, showing the effectiveness of the wavelet analysis. It is shown that, provided that the pure polymer spectral contribution is subtracted from the aqueous solutions spectra, the shape of the intramolecular O–H stretching band can be reproduced by a superposition of the spectrum of bulk water and of the spectrum of hydration water, i.e., the spectrum relative to the water molecules bonded to the polymer chain. The weight of the bonded-water spectrum changes with concentration furnishing a polymer hydration number value which well agrees with hydration number data, reported in literature, obtained with other techniques. On the other hand, the intramolecular infrared O–H stretching band and the low-frequency Raman spectra, for all the investigated polymeric aqueous solutions, when analyzed through a multiscale wavelet cross-correlation approach reveal that significant spectral changes are registered in the 0.00–0.46 water weight fraction range. Such complementary experimental and analytic findings suggest the picture that when the water content increases, the water molecules saturate the two lone pairs of each oxygen atom of the polymer furnishing a hydration number which agrees with previous determinations and hence supporting the validity of the wavelet approach.     

理想腔中具有正交偶极矩的级联型三能级原子发射谱

假设原子具有两正交跃迁电偶极矩，运用全量子论研究了与单模电磁场共振相互作用的等距三能级原子的发射谱. 对不依赖于场强耦合和依赖强度耦合两种情况分别进行了发射谱的计算，并比较了原子偶极矩正交和平行条件下发射谱的异同. 结果表明，一般情况下，具有平行偶极矩的原子的发射谱谱线少于具有正交偶极矩的原子的谱线，一些谱线由于干涉而消失. 关键词： 量子光学 发射谱 电偶极矩 级联型三能级原子     

The effect of detuning upon resonance fluorescence

The excitation spectrum of a two-level atom interacting with a strong laser field is considered as a function of the detuning. The spectral function of the system is calculated by making use of the Green's function formalism and includes a physical process which is neglected in many earlier treatments of the one photon problem. It is found that for zero and small detunings, the spectral function describes the well known three peak spectrum which evolves into a four line spectrum as the detuning is increased. Results of numerical calculations for a wide range of detuning are presented and analytic expressions are derived to describe the small and large detuning limits.     

Resonance fluorescence spectrum of a three-level atom

We consider the excitation spectrum arising from the interaction between a three-level atom and a strong electromagnetic field in the frequency region where the two atomic transition frequencies are nearly equal to once and twice the frequency of the pump field respectively. Detailed expressions for the spectral functions are derived describing the two-, one- and zero-photon excitations as well as those arising from the coupling between them, in the limit of high photon densities. The zero-photon excitations describe low frequency modes induced by the pump field under resonance conditions.     

依赖强度耦合的Λ型三能级Jaynes-Cummings模型的原子发射谱及腔场谱

在假设原子初始处于激发态并计入原子-场耦合强度依赖性的条件下,用本征函数法研究了Λ型三能级原子与单模腔场共振相互作用系统的原子发射谱和腔场谱。结果表明,基态能级裂距对谱结构有重要影响。发射谱和腔场谱的谱线随初场增强不发生合并现象,腔场谱对初场光子统计性质不敏感。     

Modification of spontaneous emission from a five-level M-type atom in coupled cavity waveguide

We study the spontaneous emission spectrum of a five-level M-type atom driven by a microwave field, in which two upper levels are coupled by the same-coupled cavity waveguide reservoir to a lower level. The spectrum behavior presents a strong non-Lorentzian shape that originates from effective quantum interference in Markovian reservoir, in which the spectral line can be significantly enhanced and eliminated by adjusting the proper parameters of the system. However, for non-Markovian reservoir, it seems that the shape of emission spectrum is quite dependent on the geometry behavior of a coupled cavity waveguide.     

Spectral shifts and spectral switches of partially coherent vector beams propagating through an astigmatic aperture lens

By using the polarization matrix and propagation equation of the cross-spectral density function matrix, the spectral shifts and spectral switches of partially coherent vector beams propagating through an astigmatic aperture lens are studied, where the effect of lens astigmatism and beam cross-correlation on the spectral switches is stressed. It is shown that the critical position, spectral transition height and spectral minimum at spectral switches depend on the astigmatism. The beam cross-correlation plays a role in spectral switches under the condition that a polarizer is inserted. The spectral switch vanishes when the astigmatic coefficient is larger than a certain value, or the cross-correlation length is less than a certain value.     

Macroscopic manifestations of specific features of quantum statistics of the radiation field in the spectrum of resonance fluorescence

The fluorescence spectrum of a two-level atom excited by the field, whose state represents a superposition of the coherent states, is investigated. It is shown that to each mode of the quantum-statistical distribution of the incident field, a spectral mode of the scattered radiation corresponds, and one can determine the number of statistical modes of the incident field from the number of spectral modes of the scattered field. This result is a consequence of the fact that in the quasi-classical limit, statistical modes of the superimposed state interact with the atom independently of one another.     

非共振耗散腔耦合系统的发射光谱

研究了非共振耗散二能级双原子与双单模腔耦合系统发射光谱的性质。探讨了原子和腔场之间的失谐、腔场衰减率及原子失相对该系统发射光谱的影响。结果表明,体系的腔场谱呈现出三重峰结构,原子发射谱呈现出二重峰结构。非共振情况时,腔场谱和原子发射谱的图像皆为非对称图像。在原子与腔场失谐时,与共振情况相比,峰位发生了明显的漂移,且中峰明显增大。增大腔场与原子的失谐,会引起边峰向低频段漂移,并改变其光谱强度;增大原子与腔场的失谐,可以使光谱整体向低频段漂移,并改变其所有峰的光谱强度。随着腔场衰减率的增大,共振情况下,会导致边峰的强度减小;失谐情况下,会导致所有峰的强度均减小。随着原子失相的增大,共振或失谐情况下,会使光谱所有峰的强度均减小。     

Absorption properties of a driven Doppler—broadened ladder system with hyperfine structure

We have studied the absorption spectrum of a Doppler-broadened ladder system,where the highest level is coupled into two middle hyperfine sublevels by a strong coherent field.We find that,when the system is considered as homogeneous,either two or three spectral components are observed,depending on the detuning of the coherent field.but when the velocity distribution of atoms is considered,we can always observe one electromagnetically induced transparency (EIT) window with high dispersion.So the atomic hyperfine structure cannot be an impediment for obtaining EIT.     

On the two-point cross-correlation function of anisotropic, spatially homogeneous ambient noise in the ocean and its relationship to the Green's function

It is well established that the free-space Green's function can be recovered from the two-point cross-correlation function of a random noise field if the noise is white and isotropic. Ambient noise in the ocean rarely satisfies either of these conditions. However, a non-uniform spectrum could be pre-whitened by the application of a suitable filter but anisotropy cannot be so readily eliminated. To investigate the effects of vertical anisotropy, three azimuthally uniform, spatially homogeneous noise fields are analyzed, two of which are idealized, while the third is representative of ambient noise in the deep ocean. In each case, the coherence function, the cross-correlation function, and the derivative of the latter with respect to the correlation delay, are derived for vertical and horizontal alignments of the sensor pair. With vertical sensors, any step-function discontinuity in the directional density function is mapped into a delta function at an appropriate time delay in the derivative (with respect to time delay) of the cross-correlation function. No such mapping occurs with horizontal sensors. In this case, only horizontally traveling noise can generate delta functions in the derivative of the cross-correlation function, and these always appear at the retarded time on either side of the origin.     

非线性光子晶体中原子辐射光场的非经典性质

讨论了非线性光子晶体微腔中二能级原子在相干场驱动下腔场的频谱特性及光子的统计性质.研究结果表明,当光子晶体的态密度很大时,如果腔场模与原子共振荧光Mollow峰的中心峰共振,则腔场的涨落压缩到量子散弹噪声之下,且与线性光子晶体微腔的情况相比其谱线峰值变大.当驱动场频率较大时光子服从亚Poisson分布,且非常接近Poisson分布.     

非线性光子晶体中原子辐射光场的非经典性质

讨论了非线性光子晶体微腔中二能级原子在相干场驱动下腔场的频谱特性及光子的统计性质.研究结果表明,当光子晶体的态密度很大时,如果腔场模与原子共振荧光Mollow峰的中心峰共振,则腔场的涨落压缩到量子散弹噪声之下,且与线性光子晶体微腔的情况相比其谱线峰值变大.当驱动场频率较大时光子服从亚Poisson分布,且非常接近Poisson分布. 关键词： 光子晶体 参量振荡 非弹性谱 二阶相关函数     

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.     

Stark效应对双模压缩真空场与原子耦合系统腔场谱的影响

研究了Stark效应对两模双光子J-C模型腔场谱的影响,推导计算出了腔场处于压缩真空态时腔场谱的计算公式和数值结果,讨论了Stark效应和初始场强对腔场谱的影响.发现初始场较弱时,Stark效应主要影响谱线的频率,对峰的强度影响不大;初始场n1=n2≥2后,Stark效应对主峰有较强的强化作用,对边峰产生抑制作用;在初始场较强时,对谱强度的影响显著.改变Stark移动参数和初始场的强度,可得到各式各样的腔场谱结构.     

级联三能级原子与单模场相互作用下的腔场谱

研究了高Q腔内级联三能级原子与单模光场相互作用模型的腔场谱.结果表明,原子初态处于上能级时，随R=g2/g1的增大,真空场的拉比峰个数按2→6→4→2→4的规律变化，在R1时，所有的拉比峰都消失.在初始场较弱时,腔场谱可出现3峰、5峰或7峰.在初始场很强时,腔场谱中只有单一的经典共振峰.如果原子初态处在中能级且R=1,腔场谱为简单的对称双峰结构，与标准J-C模型的谱相似. 关键词： 级联三能级原子 单模光场 腔场谱     

Emission Spectrum Property of Modulated Atom-Field Coupling System

The emission spectrum of a two-level atom interacting with a single mode radiation field in the case of periodic oscillation coupling coefficient is investigated. A general expression for the emission spectrum is derived. The numerical results for the initial field in pure number stare are calculated. It is found that the effect of the coupling coefficient modulation on the spectral structure is very obvious in the case of a low modulation frequency and larger amplitude when the initial field is vacuum, which is potentially useful for exploring a modulated light source.     

Structure characterization of foams and filled polymers by means of MRI

The structure of foams and filled polymers can be analyzed by means of MRI. It is also possible to observe the deformation behavior of the structure of foams and filled polymers in situ. A displacement experiment (rigid body) was performed in the magnet and observed by MRI. The NMR images are analyzed by image processing. Average distances between particles are estimated by the use of the autocorrelation function and the spectrum of the autocorrelation function. The spectrum shows the spatial frequency of the distances. The displacement field was calculated by the cross-correlation function. Information about particle distances and micromechanical deformation can be obtained by NMR imaging methods by combining autocorrelation and cross-correlation.     

Emission Spectrum Property of Modulated Atom-Field Coupling System

The emission spectrum of a two-level atom interacting with a single mode radiation field in the case of periodic oscillation coupling coefficient is investigated.A general expression for the emission spectrum is derived.The numerical results for the initial field in pure number stare are calculated.It is found that the effect of the coupling coefficient modulation on the spectral structure is very obvious in the case of a low modulation frequency and larger amplitude when the initial field is vacuum,which is potentially useful for exploring a modulated light source.