Coherent interaction of laser pulses in a resonant optically dense extended medium under the regime of strong field-matter coupling

Nonstationary pump-probe interaction between short laser pulses propagating in a resonant optically dense coherent medium is considered. A special attention is paid to the case, where the density of two-level particles is high enough that a considerable part of the energy of relatively weak external laser-fields can be coherently absorbed and reemitted by the medium. Thus, the field of medium reaction plays a key role in the interaction processes, which leads to the collective behavior of an atomic ensemble in the strongly coupled light-matter system. Such behavior results in the fast excitation interchanges between the field and a medium in the form of the optical ringing, which is analogous to polariton beating in the solid-state optics. This collective oscillating response, which can be treated as successive beats between light wave-packets of different group velocities, is shown to significantly affect propagation and amplification of the probe field under its nonlinear interaction with a nearly copropagating pump pulse. Depending on the probe-pump time delay, the probe transmission spectra show the appearance of either specific doublet or coherent dip. The widths of these features are determined by the density-dependent field-matter coupling coefficient and increase during the propagation. Besides that, the widths of the coherent features, which appear close to the resonance in the broadband probe-spectrum, exceed the absorption-line width, since, under the strong-coupling regime, the frequency of the optical ringing exceeds the rate of incoherent relaxation. Contrary to the stationary strong-field effects, the density- and coordinate-dependent transmission spectra of the probe manifest the importance of the collective oscillations and cannot be obtained in the framework of the single-atom model.Comment: 10 pages, 8 figures, to be published in Phys. Rev.

Violations of local realism by two entangled quNits are stronger than for two qubits

Tests of local realism vs quantum mechanics based on Bell's inequality employ two entangled qubits. We investigate the general case of two entangled quNits, i.e. quantum systems defined in an N-dimensional Hilbert space. Via a numerical linear optimization method we show that violations of local realism are stronger for two maximally entangled quNits (N=3,4,...,9), than for two qubits and that they increase with N. The two quNit measurements can be experimentally realized using entangled photons and unbiased multiport beamsplitters.Comment: 5 pages, 2 pictures, LaTex, two columns; No changes in the result

Resonant nonstationary amplification of polychromatic laser pulses and conical emission in an optically dense ensemble of neon metastable atoms

Experimental and numerical investigation of single-beam and pump-probe interaction with a resonantly absorbing dense extended medium under strong and weak field-matter coupling is presented. Significant probe beam amplification and conical emission were observed. Under relatively weak pumping and high medium density, when the condition of strong coupling between field and resonant matter is fulfilled, the probe amplification spectrum has a form of spectral doublet. Stronger pumping leads to the appearance of a single peak of the probe beam amplification at the transition frequency. The greater probe intensity results in an asymmetrical transmission spectrum with amplification at the blue wing of the absorption line and attenuation at the red one. Under high medium density, a broad band of amplification appears. Theoretical model is based on the solution of the Maxwell-Bloch equations for a two-level system. Different types of probe transmission spectra obtained are attributed to complex dynamics of a coherent medium response to broadband polychromatic radiation of a multimode dye laser.Comment: 9 pages, 13 figures, corrected, Fig.8 was changed, to be published in Phys. Rev.

Formation and Primary Heating of The Solar Corona - Theory and Simulation

An integrated Magneto-Fluid model, that accords full treatment to the Velocity fields associated with the directed plasma motion, is developed to investigate the dynamics of coronal structures. It is suggested that the interaction of the fluid and the magnetic aspects of plasma may be a crucial element in creating so much diversity in the solar atmosphere. It is shown that the structures which comprise the solar corona can be created by particle (plasma) flows observed near the Sun's surface - the primary heating of these structures is caused by the viscous dissipation of the flow kinetic energy.Comment: 46 pages including 7 pages of figures, Submitted to Phys.Plasma

Dense Plasma Focus: physics and applications (radiation material science, single-shot disclosure of hidden illegal objects, radiation biology and medicine, etc.)

The paper presents some outcomes obtained during the year of 2013 of the activity in the frame of the International Atomic Energy Agency Co-ordinated research project "Investigations of Materials under High Repetition and Intense Fusion-Relevant Pulses". The main results are related to the effects created at the interaction of powerful pulses of different types of radiation (soft and hard X-rays, hot plasma and fast ion streams, neutrons, etc. generated in Dense Plasma Focus (DPF) facilities) with various materials including those that are counted as perspective ones for their use in future thermonuclear reactors. Besides we discuss phenomena observed at the irradiation of biological test objects. We examine possible applications of nanosecond powerful pulses of neutrons to the aims of nuclear medicine and for disclosure of hidden illegal objects. Special attention is devoted to discussions of a possibility to create extremely large and enormously diminutive DPF devices and probabilities of their use in energetics, medicine and modern electronics

Effect of different utilization kinds of arable sandy soil on its chemical and biological properites

На пахотной песчаной аллювиальной почве опытной станции своец проводились химические и биологические исследования почвы используемой в течение 25 лет в качестве поля севооборота, черного пара и природной залежи. В сравнении с почвой поля севооборота в почве черного пара уменьшилось на около 30% содержание органического С, общего N, P₂O₅ и K₂O, а в почве залехи содержание органического С на 68%, N на 54% и СаО на 30%, при одновременном четком снижении содержания P₂O₅ и K₂O. В составе гумуса увеличилось участие фульвовых и гуминовых кислот, а уменьшилось содержание гумина в почве черного пара. В почве залежи направление изменений было обратным. Активность сахаразы и каталазы была самой сильной в почве залежи, а гораздо слабее в почве под севооборотом и черным паром. Густота Collembola и Acarina были в почве залежи двухкратно выше, чем в почве поля севооборота, а в почве черного пара наполовину меньше.Chemical and biological investigations of arable sandy soil were investigated. The investigations were carried out at the Experiment Station Swojec on the arable sandy alluvial soil utilized for 25 years as a crop rotation field, black fallow and natural wasteland. The organic C, total N, P₂O₅ and H₂O content in the soil of black fallow decreased by about 30% as compared with the soil of the crop„ rotation field, whereas in the soil of wasteland increased the content of organic C by 68%, of N by 54% and of CaO by 30% and distinctly decreased the P₂O₅ and K₂O content. In the humus composition increased the share of fulvic and humic acids and decreased the content of humins in the black fallow soil. The saccharase and catalase activity was the highest in the soil of wasteland and considerably decreased in the soil of crop rotation field and black fallow. The density of Collembola and Acarina was over twice higher in the wasteland soil than in soil on the crop rotation field and was by a half lower in the black fallow soil

On tuning mechanisms of DPF devices

A global instability theory of pinching plasmas allows us to justify the well-known empirical facts of the use of a mismatched dense plasma focus (DPF) and heavy inert gas admixtures. We assume that an instability of tangential discontinuity is responsible for the instability of a current-carrying plasma column. To inhibit development of a tangential discontinuity in a plasma focus, an array of insulator fibers or metallic wires placed on the anode near the axis of a discharge camera can be used

Frequency up-conversion and trapping of ultrashort laser pulses in semiconductor plasmas

It is shown that the interaction of ultrashort laser pulses with nonstationary semiconductor plasmas can, under appropriate conditions, lead to a variety of interesting phenomena including controlled upshifting of the laser frequency leading to the possibility of tunable lasers in a wide range of frequencies, and trapping (nonpropagation) of a substantial part of the incident pulse

On the robustness of the localized spatiotemporal structures in electron-positron-ion plasmas

It is shown that, in an electron-positron plasma with a small fraction of ions, large-amplitude localized spatiotemporal structures (light bullets) can be readily generated and sustained. These light bullets are found to be exceptionally robust: they can emerge from a large variety of initial field distributions and are remarkably stable