Steady-State Spatial Solitons in Low-Amplitude Regime in Biased Photorefractive-Photovoltaic Crystals

A theory of the space-charge field is improved in biased photorefractive-phorovoltaic crystals. Steady-state spatial solitons are obtained in the low-amplitude regime in biased photorefractive-photovoltaic crystals. When photovoltaic effect is neglected, these solitons are screening solitons, and their space-charge field is the space-charge field of screening solitons. When the external field is absent, these solitons are photovoltaic solitons for the closed or the open circuit and we also predict that gray solitons exist in photorefractive-photovoltaic crystals, and their space-charge field is the space-charge field of photovoltaic solitons.     

Antiferromagnets in a field and ferromagnets in a random field

A new mean field approach for antiferromagnets in a field is shown to be equivalent to a mean field treatment of ferromagnets in a random field. Phase diagrams of the two systems are analogous.     

Hot-Electron Magneto-Transport in InSb

The balance equations are used to investigate the hot electron magneto-transport in narrowgap semiconductor InSb at 77 K in crossed weak magnetic field and electric field. In the case of vanishing transverse velocity, the drift mobility and the Hall mobility are calculated and it is shown that the Hall factor in InSb at 77K is less than 1 and decreases with electric field. In the case of vanishing transverse electric field, the longitudinal velocity and the transverse velocity are calculated as a function of the magnetic field and the electric field. The effect of the magnetic field on the longitudinal velocity is different from that on the transverse velocity.     

Steady-State Spatial Solitons in Low-Amplitude Regime in Biased Photorefractive-Photovoltaic Crystals

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　　Ｓｔｅａｄｙ ｓｔａｔｅｐｈｏｔｏｒｅｆｒａｃｔｉｖｅ (ＰＲ)ｓｐａｔｉａｌｓｏｌｉｔｏｎｓ[1～ 3] ｈａｖｅｂｅｅｎｉｎｖｅｓｔｉｇａｔｅｄｅｘｔｅｎｓｉｖｅｌｙｉｎｔｈｅｐａｓｔｆｅｗｙｅａｒｓ.Ａｔｐｒｅｓｅｎｔｔｈｅｓｅａｒｅｔｗｏｄｉｆｆｅｒｅｎｔｋｉｎｄｓｏｆｓｔｅａｄｙ ｓｔａｔｅＰＲｓｏｌｉｔｏｎｓ :ｓｃｒｅｅｎｉｎｇ[1 ,2 ] ｓｏｌｉｔｏｎｓａｎｄｐｈｏｔｏｖｏｌｔａｉｃ (ＰＶ) [3]ｓｏｌｉｔｏｎｓ.Ｍｏｒｅｒｅｃｅｎｔｌｙ ,ｗｅｈａｖｅｓｈｏｗｎｔｈｅｏ…     

Radiative corrections in a vector-tensor model

In a recently proposed model in which a vector non-Abelian gauge field interacts with an antisymmetric tensor field, it has been shown that the tensor field possesses no physical degrees of freedom. This formal demonstration is tested by computing the one-loop contributions of the tensor field to the self-energy of the vector field. It is shown that despite the large number of Feynman diagrams in which the tensor field contributes, the sum of these diagrams vanishes, confirming that it is not physical. Furthermore, if the tensor field were to couple with a spinor field, it is shown at one-loop order that the spinor self-energy is not renormalizable, and hence this coupling must be excluded. In principle though, this tensor field does couple to the gravitational field.     

Electric Field in a Gravitational Field

The potential of a static electric charge located in a Schwarzschild gravitational field is given by Linet. The expressions for the field lines derived from this potential are calculated by numerical integration and drawn for different locations of the static charge in the gravitational field. The field lines calculated for a charge located very close to the central mass can be compared to those calculated by Hanni–Ruffini. Maxwell equations are used to analyze the dynamics of the falling electric field in a gravitational field.     

ANSYS在气体探测器电场分布计算中的应用

介绍了气体探测器电场分布的计算方法,以计算MSGC探测器单元电场分布为例说明了如何用ANSYS软件包来计算结构较复杂的气体探测器内部电场分布,同时讨论了电场分布对气体探测器性能的影响.     

Electron polarization in quantum wells in a strong variable field

The wave function of an electron in a symmetric double quantum well placed in a strong time-periodic electric field is found, expressions for quasienergy functions are derived, and the dependence of the dipole moment on the average electric field is analyzed for the case where the average field remains constant. In the case of slow monotonic variation of the “constant” component of the electric field, the Schro dinger equation is solved by the WKB method. It is found that the dependence of the dipole moment on the average field is of a clearly nonlinear almost-periodic nature and that in the event of adiabatic monotonic variation of the average field there is a periodic relocation of the electron density from well to well with a small frequency proportional to the rate of variation of the average field. Zh. éksp. Teor. Fiz. 116, 217–235 (July 1999)     

Ultrafast field dynamics in large-aperture photoconductors

We investigated field screening mechanisms in large-aperture GaAs photoconductors, using an ultrafast pump-probe terahertz technique. After photoexcitation the bias field decreases to an intensity-dependent value as a result of near-field screening of the bias field. For longer delays the field exhibits an intensity-dependent decrease that results from a space-charge field caused by transport-induced charge separation. These measurements support recent theoretical results that the dominant saturation mechanism that limits terahertz output from large-aperture photoconductors is near-field screening of the bias field because the space-charge field develops on a much longer time scale than that of the terahertz pulse.     

Rapid magnetization reversal in magnetic small particles induced by non-static bias field

Magnetization reversal processes by a switching field in single-domain nano-sized magnetic particles in the presence of a small transverse non-static bias field are studied. Applying an oscillating bias field instead of a static field, the reversal time becomes much shorter when the switching field is slightly stronger than the effective anisotropy field. A pulsed bias field of a suitably chosen duration in the nanosecond scale is found to induce a rapid switching, even when the switching field is smaller than the anisotropy field. The dependence of the reversal time on the frequency of an oscillating bias field and the duration of a pulsed bias field are studied. The present work thus complement the earlier studies on switching in the presence of a static bias field.     

Continuous-variable Entanglement in a Correlated Spontaneous Emission Laser

We discuss the generation and evolution of entangled light in a correlated spontaneous emission laser in the linear regime. The master equation for the two-mode cavity field is derived and solved analytically in phase space. The time-dependent characteristic function in the Wigner representation for the two-mode field is obtained. It shows that the two-mode field in the cavity evolves in a two-mode Gaussian state. The entanglement degree of the two- mode field in the cavity increases initially, then decreases, and finally vanishes as the field evolves from an initial vacuum. The period of the entanglement is extended as the intensity of the driving field is increased. It is found that the entanglement still exists even when the two-mode squeezing disappears. During the entanglement period, the intensity of the field is amplified. The entanglement for the initial field being a two-mode squeezed vacuum and the entanglement of the output field are also discussed.     

Theory of interband and intraband light scattering in semiconductors in an external electric field

A theory is developed for interband and intraband light scattering in semiconductors in an external electric field. Explicit results are given for a simple two-band model. The field induced change of the interband scattering cross section shows oscillation close to the scattering edge. Intraband scattering being approximately elastic without an external electric field becomes inelastic in the presence of the field. A numerical estimation of the field influence on the scattering cross section is given in both cases.     

Magnetic field effect in photodetachment from negative ion in electric field near metal surface

Based on the closed-orbit theory, the magnetic field effect in the photodetachment of negative ion in the electric field near a metal surface is studied for the first time. The results show that the magnetic field can produce a significant effect on the photodetachment of negative ion near a metal surface. Besides the closed orbits previously found by Du et al. for the H in the electric field near a metal surface (J. Phys. B 43 035002 (2010)), some additional closed orbits are produced due to the effect of magnetic field. For a given ion-surface distance and an electric field strength, the cross section depends sensitively on the magnetic field strength. As the magnetic field strength is very small, its influence can be neglected. With the increase of the magnetic field strength, the number of the closed orbits increases greatly and the oscillation in the cross section becomes much more complex. Therefore we can control the photodetachment cross section of the negative ion by changing the magnetic field strength. We hope that our results may guide future experimental studies for the photodetachment process of negative ion in the presence of external fields and surfaces.     

Numerical study of laser-induced collision process in Eu-Sr in strong field

Theoretically based on the four-level model, one LICET process in Eu-Sr system in both weak and strong fields was calculated by immediate numerical integrations. Numerical results in weak field are in fair to good agreement with analytical ones. Numerical results in strong field show that: (a) the peak of the LICET profiles moves to the violet side and the tuning range of the profiles obviously becomes narrower when the laser field intensity increases; and (b) numerical results in strong field differ a lot from analytical ones, which indicates that in strong field, the analytical expressions are not applicable any longer.     

Magnetic field driven domain-wall propagation in magnetic nanowires

The mechanism of magnetic field induced magnetic domain-wall (DW) propagation in a nanowire is revealed: A static DW cannot exist in a homogeneous magnetic nanowire when an external magnetic field is applied. Thus, a DW must vary with time under a static magnetic field. A moving DW must dissipate energy due to the Gilbert damping. As a result, the wire has to release its Zeeman energy through the DW propagation along the field direction. The DW propagation speed is proportional to the energy dissipation rate that is determined by the DW structure. The negative differential mobility in the intermediate field is due to the transition from high energy dissipation at low field to low energy dissipation at high field. For the field larger than the so-called Walker breakdown field, DW plane precesses around the wire, leading to the propagation speed oscillation.     

Selective modes excitation in multimode photonic crystal waveguides

We investigate modes excitation with the input field of different positions in two-dimensional multimode photonic crystal waveguides. Odd modes can be selectively excited by the input field of odd symmetry. The input field with different positions can excite different modes due to the field intensity distribution of modes. When the input field locates at the position of the zero field, intensity of waveguide modes is zero and the modes are not excited. The finite-difference time-domain method is used to obtain the excited field distributions.     

Chaotic imaging in frequency downconversion

We analyze and recover, by means of spatial intensity correlations, the image obtained by a seeded frequency-downconversion process in which the seed field is chaotic and an intensity modulation is encoded in the pump field. Although the field generated is as chaotic as the seed field and does not carry any information about the modulation of the pump, one can extract an image of the pump by measuring the spatial intensity correlations between the generated field and one Fourier component of the seed.     

微谐振环结构体内太赫兹增强效应

基于严格电磁场理论,给出了微型谐振环形和Fishnet结构体内太赫兹波的严格表达式,并利用电磁场的边界条件分析了太赫兹波在微型谐振环形和Fishnet结构体内空间分布的增强效应。数值模拟结果表明:谐振环金属条附近的电场大于磁场,金属条附近的电场相对其他区域明显要强得多,开口处表现更为突出,太赫兹波在Fishnet结构体内电磁场的峰位处电场和磁场分布关于x对称;电场的极值出现在大十字架的上下四个角,而磁场的极值则出现在小十字架的上下两端点。同时用电磁场传输线理论对该现象作出一定的物理解释。收稿日期:; 修订日期:     

Radiating Kerr particle in Einstein universe

A generalized Kerr-NUT type metric is considered in connection with Einstein field equations corresponding to perfect fluid plus a pure radiation field. A general scheme for obtaining the exact solutions of these field equations is developed. Two physically meaningful particular cases are investigated in detail. One gives the field of a radiating Kerr particle embedded in the Einstein universe. The other solution may probably represent a deSitter-like universe pervaded by a pure radiation field.     

Generation of Electric Field and Net Charge in Hall Reconnection

Generation of Hall electric field and net charge associated initial conditions of plasma density and magnetic field. with magnetic reconnection is studied under different With inclusion of the Hall effects, decoupling of the electron and ion motions leads to the formation of a narrow layer with strong electric field and large net charge density along the separatrix. The asymmetry of the plasma density or magnetic field or both across the current sheet will largely increase the magnitude of the electric field and net charge. The results indicate that the asymmetry of the magnetic field is more effective in producing larger electric field and charge density. The electric field and net charge are always much larger in the low density or/and high magnetic field side than those in the high density or/and low magnetic field side. Both the electric field and net charge density are linearly dependent on the ratios of the plasma density or the square of the magnetic field across the current sheet. For the case with both initial asymmetries of the magnetic field and density, rather large Hall electric field and charge density are generated.