Light scattering by nanosized systems with different spatial organizations

The integrodifferential equation method is used to study the spectrum of a nanoparticle colloid for the example of interaction of three arbitrarily arranged dielectric particles made up of nonresonant atoms (the eigenfrequency of the transition is far from the emission frequency) with incorporated barium atoms in an external optical radiation field. The effect on the light-scattering properties of a nanosphere in the ensemble of its distant “neighbors” is studied; an additional peak associated with them is observed as a frequency close to the resonance for an isolated nanosphere, which under certain conditions has higher intensity than the main peak corresponding to optical near-field resonance in a two-particle system. The dependence of the spectrum of the nanosized system on the geometric structure is studied, and it is shown that very precise tuning of the resonance frequency is possible by varying the angular distribution of the particles. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 5, pp. 641–646, September–October, 2006.     

虚光场效应对原子激光压缩性质的影响

在压缩真空态光场和二能级原子玻色-爱因斯坦凝聚体相互作用系统中, 应用全量子理论, 分别在旋波近似和非旋波近似下, 研究了原子激光的压缩特性以及原子本征频率、光场-原子的耦合系数、光场初始压缩因子以及虚光场对原子激光压缩特性的影响. 研究表明,原子激光的两个正交分量均可被周期性压缩,原子的本征频率决定了原子激光两个正交分量涨落的量子Rabi频率,光场与原子的耦合系数决定了原子激光正交分量涨落的崩塌-回复振荡频率,当光场初始压缩因子增大和考虑虚光场效应时,原子激光正交分量的压缩深度均加深. 关键词： 玻色-爱因斯坦凝聚 压缩真空态 原子激光 虚光场效应     

Modified Bloch Equations for Subsystems of Two-Level Atoms

Modified Bloch equations that describe the interaction of high-power optical radiation with a dense resonance medium consisting of two subsystems of different two-level atoms of high density are obtained. It is shown that, unlike the one-component resonance medium in which the effect of internal optical bistability manifests itself on the red wing of the absorption line, in the two-component system it appears on the blue wing of one component of the system. The switching of the two subsystems from one steady state to another occurs at the same points of rotation of the hysteresis dependence of the population differences of resonance atomic levels on the radiation intensity that varies adiabatically slowly. The influence of the processes of upconversion on the spectral-threshold characteristics of the effect of internal optical bistability is investigated.     

Effect of driving laser intensity fluctuations on optical bistability of a system with large permanent-dipole molecules

The statistical properties of an optical bistable system consisting of two-level atoms with large permanent dipole moments contained in a Fabry-Perot cavity are investigated assuming the external laser intensity fluctuations to be the main source of noise. The probability transformation rule is applied to obtain the probability distribution for the transmitted intensity whereas the probability distribution for the incident intensity is assumed to be that of the partially coherent laser light. It turns out that in the optical bistability region two values of fluctuation parameters are possible for a given value of input intensity, which produces interesting hysteresis effects.     

Method of resonance near-field optical microscopy

We have solved the problem in which a thin metal wafer (probe) with a nanohole interacts with the flat surface of a metastructured film consisting of metal nanoparticles in an external optical radiation field. Nanoparticles are considered as two-level atomic systems. This interaction of the wafer-probe and the flat surface in the external optical radiation field gives rise to optical near-field resonance, the frequency of which differs significantly from the natural frequencies of two-level atoms in the medium and the probe. The fields inside and outside the probe and metastructured film are calculated in the near-field and far-field zones. The maximum resolution, which is achievable in the suggested scheme of near-field optical microscopy, can reach about 10 nm. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 4, pp. 499–506, July–August, 2007.     

原子在弱相干场光纤耦合腔系统中的纠缠特性

研究由两个相同的二能级原子分别处于用单模光纤耦合的两弱相干光场系统的共生纠缠特性, 通过数值计算研究了光纤模-腔模与原子-腔模的耦合强度比、弱相干光场的强度和两光场相对相位差等因素对系统纠缠演化的影响. 结果表明: 两腔中的两原子之间、两光场之间和每个腔中的原子与光场之间的纠缠随时间呈现周期或准周期性演化, 两腔场之间的纠缠与腔中的两原子的纠缠可以相互转换, 与两原子之间和两光场之间的纠缠相比, 每个腔中光场与原子之间的纠缠随时间变化的周期缩短. 光纤模-腔模与原子-腔模的耦合强度比与两腔中光场相位差对系统纠缠的影响很大, 较小的光纤模-腔模与原子-腔模的耦合强度之比可以获得较大的系统纠缠度. 关键词： 弱相干场 光纤耦合腔 耦合强度 量子纠缠     

Untersuchung an einem Theta-Pinch-Plasma im Bereich der Plasmafrequenz

It is investigated to what extent the radiation of a thetatron plasma near the plasma frequency can be interpreted by means of Bremsstrahlung emission. A new type of infrared scanning system allowing for radial resolution of the plasma radiation around 2.5 THz was designed for this purpose. The radiation intensities measured herewith are compared with the results of a computer program. This program based on an experimentally verified hydromagnetic model gives the time-dependent Bremsstrahlung intensity in a ray optical approximation; supplementary computations have been carried out in wave optical approximations. The results of both calculations are in good agreement with the infrared measurements except for a short radiation peak during the first shock wave phase of the discharge. This peak can be interpreted, however, by means of a semiquantitative evaluation as a two-stream instability-induced radiation burst.     

The near-field effect in a system of two-level dipole particles

We have solved a self-consistent problem on interaction of two dipole atoms located at an arbitrary distance from each other with the field of a quasiresonance light wave, whose intensity is sufficient for the system to manifest nonlinear properties. The atoms are considered as two-level systems described by means of Bloch optical equations, while the field inside of the system includes both Coulomb and retarded parts. We consider a situation where atoms are identical and the distance between them is much smaller than the length of an outer light wave. The distribution of an electric field both inside of a small object and outside of it is found numerically. It is shown that the amplitude of the electric field in a wave zone depends substantially on the frequency of the external field and interatomic distance, while the field distribution differs from the field pattern of an electric dipole. At definite values of the external field intensity an optical multistability is a feature of the system under investigation. We have elucidated the conditions under which the multistability is manifested in the present system. The results obtained are considered as the near-field effect in the optics of small objects, which makes it possible to investigate the structure of small objects by means of optical radiation. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 3, pp. 375–378, May–June, 2000. The present work was supported by the Russian Foundation for Fundamental Research (grant 98-02-16035) and by a grant from the Federal Purpose-Oriented Program “Integration.”     

W类态三纠缠原子与相干态光场相互作用过程中光场的量子特性

研究了处于W类态的三纠缠原子与相干态光场相互作用过程中光场的量子特性;运用数值方法,讨论了三纠缠原子初始状态和相干态光场的强弱对系统光场压缩和二阶相干特性的影响。     

Structure and optical properties of lead iodide based two-dimensional perovskite compounds containing fluorophenethylamines

Phenethylammonium-based perovskites, which can be regarded as a semiconductor/insulator multiple quantum well consisting of lead halide semiconductor layers sandwiched between phenethylammonium insulator layers were prepared. To investigate the effects of the electronic state and the orientation of organic insulator layers on the optical properties of layered perovskites, fluorine substituted analogues were also prepared. The structure and optical properties were investigated by the XRD, UV–Vis absorption, and fluorescence measurements. The exciton absorption peak was shifted by the substitution of fluorine atoms in organic ammonium compounds. It became clear that the optical properties of two-dimensional perovskite compounds were controlled by the substitution of fluorine atoms.     

Coherent backscattering under conditions of pulsed radiation trapping

Coherent backscattering of pulsed radiation emitted by optically dense atomic ensembles is considered. The diagrammatic technique is used for deriving analytic expressions for correlation functions of scattered light, which make it possible to take into account all main factors affecting the dynamics of the process, including the hyperfine and Zeeman structure of the ground and first excited states of atoms, polarization of probe radiation, the actual shape and size of an atomic cloud, its spatial inhomogeneity, motion of atoms, and angular-momentum polarization of atoms. On the basis of these relations, the time dependence of the total intensity and the dependence of enhancement factor of backscattered light on the pulse duration, type of polarization of the polarization system of observation, optical thickness of the scattering medium, and the carrier frequency of the pulse are investigated. The calculations are performed for an ensemble of rubidium-85 atoms cooled in magnetooptical traps.     

三维光学晶格中铯原子的装载与冷却

建立了四光束的三维光学晶格势场,在铯原子磁光阱和光学粘团的基础上实现了红失谐三维光学晶格中冷原子的装载.借助于短程飞行时间吸收谱测量冷原子温度,通过改变光学晶格的总光强和频率失谐等条件,对光学晶格中铯原子的亚多普勒冷却以及光学晶格中冷原子的寿命进行了研究. 关键词： 光学晶格 磁光阱 光学粘团 冷原子     

The production of excimer molecules and excited atoms in a positive corona discharge in He/Xe(Kr)/SF6/CCl4 mixtures

Electrical and optical characteristics of a positive corona discharge in He/Xe(Kr)/SF₆/CCl₄ mixtures, which are of interest for the use in multiwavelength excimer radiation sources, are studied in the needle-grid electrode configuration. The length of the discharge, which is usually used to pump repetitive high-pressure multiwavelength radiation sources, is equal to the length of the electrodes of an excimer laser or lamp pumped by a transverse electric discharge. The discharge current-voltage and frequency characteristics, panoramic emission spectra, and the dependences of the relative emission intensity from the halogenides and excited noble gas atoms on the corona discharge current are investigated. The main processes resulting in the production of halogenides, as well as xenon and krypton excited atoms, in the generation regions of a corona discharge are studied.     

Dipole emission of a nanostructure system composed of two atoms and dimensional resonances

A stationary solution is obtained for the joint system of equations for atomic and field variables for two different atoms with dipole-dipole interaction in the radiation field taking into account the common radiative friction. The atoms are treated as an Lorentz oscillator with one isolated resonance. The interaction of atoms in the radiation field forms four dimensional resonances at frequencies that are substantially different from the natural frequencies of isolated atoms. Two of the four dimensional resonances are characterized by negative dispersion, and the intensity of dipole emission at these frequencies may be increased with respect to the intensity of emission at the frequencies of natural atomic resonances by a factor of about 10¹².     

等同双原子Jaynes-Cummings模型的量子特性及系统光谱

在全量子理论的背景下提出两个二能级原子分别与一单模腔场相互作用的系统模型,利用量子主方程和数值模拟计算等方法,研究该体系中腔场平均光子数、Mandel's Q因子及二阶量子相关度在非稳态时的变化规律。此外,对体系中原子及腔场中光谱结构进行了分析。结果表明:减小腔场耗散系数,增大原子间耦合系数,体系量子特性愈加明显。体系光谱呈现出Mollow三重峰结构,且原子辐射谱强度远大于腔场辐射谱强度。当原子跃迁频率与腔场跃迁频率为近共振时,Mollow峰值为三峰中最大值。此外,增大原子与腔场间耦合系数,可增大原子光谱的中峰强度;而增大腔场光谱的中峰强度,则需减小原子与腔场间耦合系数。     

Scattering tightly bound dimers off a scattering potential

The motion of two attractively interacting atoms in an optical lattice is investigated in the presence of a scattering potential. The initial wavefunction can be prepared by using tightly bound exact two-particle eigenfunction for vanishing scattering potential. This allows to numerically simulate the dynamics in the generation of two-particle Schrödinger cat states using a scheme recently proposed for scattering of quantum matter wave solitons.     

High frequency intensity noise spectra of axial mode groups in the radiation from CW GaAIAs diode lasers

The dependence of the intrinsic random intensity noise spectrum of the radiation from CW DH GaAIAs diode multimode lasers on optical wavelength has been investigated for the first time in a wide frequency range 30 MHz to 3 GHz. It was generally observed, that a lasing mode which is optically isolated from the rest of the radiation, shows much stronger intensity fluctuations as compared to the fluctuations of the total output, particularly in the frequency range below the intrinsic natural resonance frequency of the laser. The magnitude of the fluctuations decreases when the number of modes in the detected radiation increases. Our experimental results are compared to computer solutions which were obtained with a simple, analytical laser noise model. Good qualitative agreement between theory and experiment is demonstrated.     

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。     

Dynamics of moving interacting atoms in a laser radiation field and optical size resonances

The forces acting on interacting moving atoms exposed to resonant laser radiation are calculated. It is shown that the forces acting on the atoms include the radiation pressure forces as well as the external and internal bias forces. The dependences of the forces on the atomic spacing, polarization, and laser radiation frequency are given. It is found that the internal bias force associated with the interaction of atomic dipoles via the reemitted field may play an important role in the dynamics of dense atomic ensembles in a light field. It is shown that optical size resonances appear in the system of interacting atoms at frequencies differing substantially from transition frequencies in the spectrum of atoms. It is noted that optical size resonances as well as the Doppler frequency shift in the spectrum of interacting atoms play a significant role in the processes of laser-radiation-controlled motion of the atoms.     

Optical holography of nanostructure diatomic objects for different polarizations of the external wave and dimensional resonances

For the combined system of equations of field and atomic variables for two different atoms in the ground state, a stationary solution is obtained, which takes into account their dipole-dipole interaction in the field of external emission. Atoms are treated as linear dipole oscillators with different natural frequencies and linear polarizabilities. Formulas for effective polarizabilities of atoms in a nanostructure object, whose dispersion properties substantially differ from the dispersion properties of isolated atoms in the region of their natural resonances, are obtained. It is found that a nanostructure object consisting of two different atoms has four dimensional resonances, whose frequencies strongly depend on the interatomic separation and the object orientation with respect to the direction of propagation of an external wave. Using interference from the coherent field of dipoles of a small object with a reference coherent wave in a certain plane of observation points in the wave region far from a small object, an optical hologram of a small object is obtained. It is shown by numerical experiments that a small object forms interference fringes with good contrast, which makes possible the use of optical quasi-resonant emission for the development of a nondestructive method of study of small objects.