Fluorescence spectra of uranium induced by a linearly polarized laser light in a magnetic field

In this paper we reported the fluorescence spectra of U~(238) induced by a linearly polarized laser field in a magnetic field and offered a theoretical analysis. The consistence between the theoretical prediction and experimental results was satisfactory.     

半导体泵浦铷蒸气激光实现线偏振基模输出

采用2400 1/mm的平面光栅搭建Littrow外腔压窄半导体激光器输出激光线宽,获得中心波长可调的线宽0.16 nm的半导体激光作为铷蒸气激光的泵浦源.实验中,使用斩波器将泵浦光变为脉宽1 ms,重复频率100 Hz的重复脉冲形式,聚焦进长度为8 mm的铷蒸气泡,泡内充入79 kPa甲烷作为缓冲气体.进入铷蒸气泡的泵浦光峰值功率为1.84 W时,控制铷泡温度在125℃,获得了峰值功率17.5 mW的基模线偏振铷激光输出.     

Photofission induced by linearly polarized photons

The asymmetry coefficients of fragments’ angular distribution (FAD) for fission of ^{234, 236, 238}U and ^{238, 240, 242}Pu isotopes, induced by linearly polarized photons, have been calculated. The optimal energies for observing the polarization parts in this asymmetry are found. Based on the experimental data on FAD for ²³²Th photofission induced by linearly polarized photons with the maximum energy E _γ = 10 MeV (with neglect of the contribution of absorption of electric quadruple photons), it is shown that the theoretical and experimental FAD asymmetry coefficients coincide within standard deviations. Original Russian Text ? S.G. Kadmensky, L.V. Titova, O.S. Khmelevskaya, 2009, published in Izvestiya Rossiiskoi Akademii Nauk. Seriya Fizicheskaya, 2009, Vol. 73, No. 6, pp. 878–881.     

Laser Compton scattering for a linearly polarized laser

Laser Compton light sources are potential candidates for the next generation of high-brightness X or γ-ray sources. When increasing the laser power to obtain intense X-ray laser, nonlinear Compton scattering happens. Nonlinear Compton scattering of linearly polarized laser beam is discussed in this paper. A complete transition probability formula is introduced and the polarization properties of final photons are discussed for different conditions.     

Laser Compton scattering for a linearly polarized laser

Laser Compton light sources are potential candidates for the next generation of high-brightness X or γ-ray sources. When increasing the laser power to obtain intense X-ray laser, nonlinear Compton scattering happens. Nonlinear Compton scattering of linearly polarized laser beam is discussed in this paper. A complete transition probability formula is introduced and the polarization properties of final photons are discussed for different conditions.     

1.5kW全光纤线偏振激光器

报道了一台全光纤结构的1.5kW线偏振光纤激光器。激光器采用振荡器结合一级放大的主振荡功率放大器(MOPA)方案。振荡器中心波长为1080nm,工作时输出功率30 W,经放大器一级放大后实现近衍射极限输出,功率达到1.5kW,光-光效率81.5%,消光比13.8dB。这是目前线偏振光纤激光器输出功率的最高值。     

Ionization of a hydrogen-like ion by a strong low-frequency linearly polarized laser field

The influence of the long-range Coulomb potential on the ionization rate of a hydrogen-like ion has been investigated within the framework of the quasi-classical method. In a rather strong field, the dependence of the ionization rate on the field intensity does not have a purely power-law character in the multiphoton region. The analytical equations obtained are in agreement with the experimental data on the cross section of multiphoton ionization and give an estimate of the threshold field values in the tunneling region.     

Acceleration of ions with a nonadiabatic linearly polarized laser pulse

Acceleration of ions during interaction of a nonadiabatic laser pulse (i.e., a pulse with a sharp front) with a nanofilm is considered. If the amplitude of such a pulse is large enough, all electrons are removed from the target at the beginning of interaction and an energy of the most energetic ions follows approximately a parabolic law with time. Two main physical mechanisms limiting the maximal ions energy are identified and investigated in detail with the help of two-dimensional (2D) particle-in-cell (PIC) simulations. The first effect is a compensation of the ions charge due to the longitudinal return of the electrons to their initial position. The second effect is the compensation of the ions charge in the laser spot due to the transverse motion of the electrons from the periphery of the target. The theory for both effects is developed and a good agreement with the 2D PIC results is established. This theory allows predicting the optimal parameters for ions acceleration.     

Quantum pump effect induced by a linearly polarized microwave in a two-dimensional electron gas

A quantum pump effect is predicted in an ideal homogeneous two-dimensional electron gas (2DEG) that is normally irradiated by linearly polarized microwaves (MW). Without considering effects from spin-orbital coupling or the magnetic field, it is found that a polarized MW can continuously pump electrons from the longitudinal to the transverse direction, or from the transverse to the longitudinal direction, in the central irradiated region. The large pump current is obtained for both the low frequency limit and the high frequency case. Its magnitude depends on sample properties such as the size of the radiated region, the power and frequency of the MW, etc. Through the calculated results, the pump current should be attributed to the dominant photon-assisted tunneling processes as well as the asymmetry of the electron density of states with respect to the Fermi energy.     

All-fiber linearly polarized laser oscillator by fiber coiling loss control

In this paper,we demonstrate an all-fiber linearly polarized fiber laser oscillator.The single polarization of the oscillator is achieved through the careful designing of the active fiber coiling.The relationship between fiber coiling diameter and polarization extinction ratio and optical efficiency is studied,whose results lead to an optimized system.The thermal management of the oscillator is also refined,which allows the oscillator to reach a maximum output power of44.1 W with an optical-to-optical efficiency of 57.9%.A high average polarization extinction ratio of 21.6 d B is achieved during a 2-hour stability test.The oscillator also owns a narrow 3-d B bandwidth of 0.1 nm,as well as near-diffraction-limit beam quality of M~2~ 1.14.     

非相对论线偏振激光下的J×B加热

利用解析的方法研究了非相对论线偏振激光与等离子体相互作用中的J×B加热吸收机理,建立了一种包含两类有质动力效应在内的自洽理论.探讨了密度轮廓修正下的J×B加热机理,给出了相应的吸收系数随激光场强度变化的关系曲线.研究发现,当激光场强度A0=20时,J×B加热所导致的吸收系数fabs约为2.8%.     

The above-threshold ionization spectrum in a strong linearly polarized laser field

We use the saddle-point method to derive analytical expressions for the spectral-angular probability distributions of the ionization by a strong linearly polarized laser field in Keldysh’s model that are valid for an arbitrary electron energy and adiabaticity parameter. We obtain asymptotic expansions of the general formulas in the multiphoton and tunneling regimes, analyze their accuracy, and formulate the validity conditions. We provide literal estimates of the parameters that characterize the properties and evolution of the distributions.     

Natural orbitals of helium in linearly polarized laser fields

Practicable equations of motion for the natural orbitals of a spin-singlet helium atom in a linearly polarized laser field are presented. The cylindrical symmetry of the two-electron problem with quantum number M = 0 is shown to yield a sparse expansion of natural orbitals in spherical harmonics. This optimization facilitates the propagation of renormalized natural orbitals of the helium atom. As a demonstration, the equations of motion are solved for a high-harmonic-generation process. In addition to the expected plateau from the single-active-electron picture, the spectrum of emitted radiation features a second plateau at higher harmonic orders.     

New manifestation of atomic parity violation in cesium: a chiral optical gain induced by linearly polarized 6S-7S excitation

We have detected, by using stimulated emission, an atomic parity violation (APV) in the form of a chiral optical gain of a cesium vapor on the 7S-6P(3/2) transition, consecutive to linearly polarized 6S-7S excitation. We demonstrate the validity of this detection method of APV, by presenting a 9% accurate measurement of expected sign and magnitude. We stress several advantages of this new approach which fully exploits the cylindrical symmetry of the setup. Future measurements at the percent level will provide an important cross-check of an existing more precise result obtained by a different method.     

Dynamic study of compressed electron layer driven by linearly polarized laser

The dynamics of the compressed electron layer(CEL) are investigated when a linearly polarized(LP) laser pulse irradiates a plasma target. The turbulent motion of the CEL is investigated by a simple model, which is verified by particlein-cell(PIC) simulations. It is found that the compressed layer disperses in a few cycles of the laser duration, because the CEL comes back with a large velocity in the opposite direction of the laser incident. A larger wavelength laser can be used to tailor the proton beam by reducing the turbulence of the CEL in the region of the LP laser acceleration.     

Angular scattering diagrams of linearly polarized relativistic-intensity electromagnetic radiation in a plasma

Instability of the propagation of nonlinear nonmonochromatic relativistic-intensity electromagnetic waves in a cold subcritical-density plasma is analyzed in three-dimensional geometry. Angular diagrams of their scattering are presented. The calculations show that forward and backward scattering may occur. The radiation in a specific direction is a set of harmonics, propagating against a continuum background, whose frequencies depend on the angle. Radiation at a specific frequency propagates in a set of scattering cones. The azimuthal cone angles depend on frequency. Zh. éksp. Teor. Fiz. 116, 1947–1962 (December 1999)     

Amplification of a weak circularly polarized light signal in a multilevel atomic medium

Amplification of a weak circularly polarized light signal in a multilevel atomic medium excited by a strong linearly polarized resonant radiation is studied. A strong optical pumping may lead to the population inversion between magnetic sublevels of hyperfine components of the ground and excited states. Solution to the self-consistent system of density matrix equations and Maxwell equations for propagation of the weak signal allows analyzing optimum conditions of amplification.     

Nonlinear interaction of linearly polarized laser radiation with condensed media and overcoming the diffraction limit

We have analyzed known experimental results on the formation of periodic structures in condensed media under the action of a series of femtosecond linearly polarized laser pulses. The found examples of the formation of spatial periods of structures with a scale smaller than the diffraction optical limit in the condensed medium have been interpreted in terms of a nonlinear mathematical model, a one-dimensional unimodal logistic mapping that describes how a change in the period that is multiple of two depends on the changing control parameter.