Nonlinear surface waves in a symmetrical three-layer structure caused by the generation of excitons and biexcitons in semiconductors

A theory of nonlinear TE-polarized surface waves propagating along the flat interfaces of a symmetric flat three-layer structure with a linear core and nonlinear coatings is developed. The coatings are nonlinear due to the optical exciton-biexciton conversion. The dispersion laws of the propagating waves are found and analyzed.     

Scattering of electromagnetic waves from nonlinear thin dielectric coatings

In this paper the reflection and diffraction properties of nonlinear thin dielectric coatings are investigated. A quite simple geometry consisting of two semi-infinite homogenous linear spaces separated by a non-linear coating is considered. An incident plane wave propagating along the z direction towards the nonlinear thin coating is taken. The nonlinear thin coating is divided into elementary sectors, within each one of which one propagating and one reflected wave exists. The boundary conditions are then applied in order to develop an efficient numerical alogirthm to study the properties of the nonlinear thin coating.     

Nonlinear TE-polarized quasi-surface waves in a symmetric optical waveguide with a nonlinear core

A theory of nonlinear polarized symmetric quasi-surface waves in a symmetric planar structure with a nonlinear core and linear coatings has been proposed. The nonlinearity of the core is caused by exciton-photon interaction and optical exciton-biexciton conversion. The dispersion laws for propagating waves have been obtained and studied.     

Laser-based linear and nonlinear guided elastic waves at surfaces (2D) and wedges (1D)

The characteristic features and applications of linear and nonlinear guided elastic waves propagating along surfaces (2D) and wedges (1D) are discussed. Laser-based excitation, detection, or contact-free analysis of these guided waves with pump–probe methods are reviewed. Determination of material parameters by broadband surface acoustic waves (SAWs) and other applications in nondestructive evaluation (NDE) are considered. The realization of nonlinear SAWs in the form of solitary waves and as shock waves, used for the determination of the fracture strength, is described. The unique properties of dispersion-free wedge waves (WWs) propagating along homogeneous wedges and of dispersive wedge waves observed in the presence of wedge modifications such as tip truncation or coatings are outlined. Theoretical and experimental results on nonlinear wedge waves in isotropic and anisotropic solids are presented.     

Nonlinear Characteristics of an Intense Laser Pulse Propagating in Partially Stripped Plasmas

The nonlinear optic characteristics of an intense laser pulse propagating in partially stripped plasmas are investigated analytically. The phase and group velocity of the laser pulse propagation as well as the three general expressions governing the nonlinear optic behavior, based on the photon number conservation, are obtained by considering the partially stripped plasma as a nonlinear optic medium. The numerical result shows that the presence of the bound electrons in partially stripped plasma can significantly change the propagating property of the intense laser pulse.     

Nonlinear Characteristics of an Intense Laser Pulse Propagating in Partially Stripped Plasmas

The nonlinear optic characteristics of an intense laser pulse propagating in partially stripped plasmas are investigated analytically. The phase and group velocity of the laser pulse propagation as well as the three general expressions governing the nonlinear optic behavior, based on the photon number conservation, are obtained by considering the partially stripped plasma as a nonlinear optic medium. The numerical result shows that the presence of the bound electrons in partially stripped plasma can significantly change the propagating property of the intense laser pulse.     

高功率微波低电离层传输的聚焦和散焦特性

 基于高功率微波(HPM)混合气体传输模型,系统阐述了考虑磁效应条件下HPM窄波束在低电离层中传输时的聚焦与散焦原理,推导了考虑外加磁场和HPM热效应情况下,窄波束在低电离层中传输的非线性几何光学方程及聚焦和散焦特性描述参数,并对低电离层中的波束发散特性进行了仿真分析。仿真结果表明：低电离层表现出的散焦特性,使HPM窄波束发散,L,R,O,X波均发生了波束发散现象,且R波的波束发散角最大,O,X波次之,L波最小,但随着入射波频率的增加,这种差别逐渐减小;相同条件下,入射波频率越高,散焦现象越弱;一定入射波频率条件下,波束轴线上的场强越大,波束发散现象越明显。     

Nonlinear propagation of ultraslow pulses in media with electromagnetically induced transparency

The nonlinear behavior of a probe pulse propagating in a medium with electromagnetically induced transparency is studied both numerically and analytically. A new type of nonlinear wave equation is proposed in which the noninstantaneous response of nonlinear polarization is treated properly. The resulting nonlinear behavior of the propagating probe pulse is shown to be fundamentally different from that predicted by the simple nonlinear Schr?dinger-like wave equation that considers only instantaneous Kerr nonlinearity.     

Asymmetry in Negative Refraction of Nonlinear Waves

Recently, inwardly propagating waves (called antiwaves, AWs) in nonlinear oscillatory systems have attracted much attention. An interesting negative refraction phenomenon has been observed in a bidomain system where one medium supports forwardly propagating waves (normal waves, NWs) and the other AWs. In this paper we find that negative refraction (NR) in nonlinear media has an asymmetric property, i.e., NR can be observed only by applying wave source withproper frequency to one medium, but not the other. Moreover, NR appears always when the incident waves are dense and the refractional waves are sparse. This asymmetry is a particular feature for nonlinear NR, which can neither be observed in linear refraction processes (both positive and negative refractions) nor in nonlinear positive refraction. The mechanism underlying the asymmetry of nonlinear NR are fully understood based on the competition of nonlinear waves.     

Parametric excitation of traveling waves in a circular non-dispersive medium

This paper discusses a special type of propagating waves created by parametric excitation in a circular taught string. The string, being a non-dispersive medium propagates deformations in a similar manner to electromagnetic waves in vacuum, both have simple wavelength–frequency relationship that play an important role here. Nonlinear equations are derived under the assumption of finite deformations, whose solution produces a square-wave like, limited-amplitude, traveling wave. Closed-form expressions are obtained for the parametric excitation characteristics of the nonlinear system and the steady-state traveling waves are described by a generalized eigenvalue problem. The latter relates the nonlinear elongation of the neutral axis to the participating wavelengths forming the propagating wave. Detailed numerical simulations are provided to validate the solution and to illustrate graphically the waveforms. It is shown that propagating sinusoidal parametric excitation gives rise to various square-wave like deformation shapes which a unique phenomenon is arising in non-dispersive media.     

无缝钢轨中温度对应力非线性超声检测的影响

研究了温度与应力共同作用下的非线性超声响应规律。构建了纵波在无缝钢轨内传播的数学模型,将传统原子间势能引入非线性波动方程,得到了无缝钢轨在自由状态及受约束状态两种情况下超声非线性系数随温度变化的函数关系。在理论分析的基础上,进行了无缝钢轨受约束时内部温度应力变化的实物模拟实验,获得的非线性系数变化趋势与理论预期相一致。研究结果表明:温度和应力都对固体介质非线性影响明显,介质非线性系数随着温度的升高而增大,随着内部压应力的增加而减小。因此,当利用非线性系数检测钢轨纵向应力时,需要对温度的影响进行补偿。      

Nonlinear electrostatic waves in a magnetized plasma

The modulational interaction of finite-amplitude high-frequency electrostatic waves propagating at an arbitrary angle to an external magnetic field with slow plasma motion is considered. A set of nonlinear evolution equations describing the interaction is obtained. New types of solitary waves propagating at near sonic speeds are found.     

Nonlinear asymmetric waves induced in a symmetrical three-layer structure by the generation of excitons and biexcitons in semiconductors

A theory of asymmetric TE-polarized quasi-surface waves propagating inside a symmetrical planar three-layer structure with a linear core and nonlinear plates is developed. The nonlinearity of the plates is associated with the inclusion of the optical exciton-biexciton conversion. The dispersion laws of the propagating waves are derived and investigated.     

线性偏振激光在相对论等离子体中的调制不稳定性

 从相对论等离体中电磁波的非线性色散方程出发,利用Karpman方法获得了线性偏振波模所满足的非线性控制方程,在非线性色散方程和非线性控制方程的基础上对线性偏振激光在相对论等离体中传播的调制不稳定性进行分析,给出了调制不稳定的时间增长率与扰动态波数之间的函数关系。     

Dynamics of whistler spheromaks in magnetized plasmas

Recent laboratory experiments [Stenzel et al., Phys. Rev. Lett. 96, 095004 (2006)10.1103/PhysRevLett.96.095004] have demonstrated interesting phenomena of propagating nonlinear whistler structures (spheromaks) and stationary field-reversed configurations, whose magnetic fields exceed the ambient magnetic field strength. Our objective here is to present simulation studies for these nonlinear whistler structures based on the three-dimensional nonlinear electron magnetohydrodynamic equations. The robustness and longevity of the propagating whistler spheromaks found in the experiments are confirmed numerically. Varying the toroidal field of the spheromak in the initial conditions, we find that the polarity and the amplitude of the toroidal field determine the propagation direction and speed of the spheromak. Our simulation results are in excellent agreement with those observed in the laboratory experiments.     

Self-action of ultrasonic pulses in a marble rod

The nonlinear effects due to the self-action of finite-amplitude ultrasonic pulses (limitation of both amplitude and carrier phase delay) propagating in a marble rod are studied experimentally and theoretically. On the basis of the measured amplitude dependences, a nonlinear equation of state is proposed for the propagation medium. With the use of this equation, the experimental results are analytically described and the nonlinear parameters of marble are determined. It is shown that the dissipative and reactive high-frequency nonlinearities of marble are caused by different mechanisms.     

Self-localized nonlinear surface magnetic polaritons in a ferromagnetic medium

The properties of electromagnetic waves propagating in a semibounded, nonlinear, ferromagnetic medium are investigated. It is shown that under certain conditions the interaction between the spin and electromagnetic waves results in the localization of volume polaritons near the surface. Self-localization of surface polaritons due to the nonlinear properties of the medium occurs thereby. The nonlinear Schrödinger equation for nonlinear surface and volume polaritons is derived, and the conditions under which solitons of these waves exist are determined. The wave intensity required to observe the predicted effects is estimated.     

Nonlinear wave processes in media containing cracks partially filled with a viscous liquid

A nonlinear (in the cubic approximation) relaxation equation of state is derived for a rod containing cracks partially filled with an incompressible viscous liquid. The nonlinear effects of the self-action and interaction of low-and high-frequency longitudinal elastic waves propagating in such a rod are studied for the cases of identical and size-varied cracks. Linear and nonlinear acoustic parameters characterizing the self-action and interaction of elastic waves in a cracked rod are determined.     

克尔介质中超连续谱的产生与自聚焦的抑制

 从（3+1）维非线性薛定谔方程出发,理论上分析了超短脉冲频谱展宽与自聚焦的影响因素。分析得出：通过改变泵浦光的功率和光束口径,可以实现光谱的极大展宽并避免自聚焦成丝。数值模拟了小口径强泵浦光束在BK7玻璃中的传输过程并进行了实验验证。模拟结果显示在超连续谱产生的同时小尺度调制被完全抑制。实验结果表明：降低泵浦光功率,使光束不会因为全光束自聚焦而发生塌陷,同时还能控制除自聚焦外的其它非线性效应,进而改善近场光束质量。由于自相位调制是超短超强脉冲产生超连续谱的重要机制之一,需要维持传输过程中的泵浦光功率,由此最佳的入射光功率应选在全光束自聚焦功率阈值附近。     

Nonlinear effects on the propagation of waves in a magnetizedrotating plasma

The nonlinear dispersion relation for an electromagnetic wave propagating through a cold, homogeneous magnetized rotating plasma is derived to investigate certain nonlinear effect for the case where only the Coriolis force part of the consequences of rotation is taken into account. Characteristics of variation of refractive indices with variation of the wave amplitude and rotational frequency are discussed. It is shown that the nonlinear effects considerably influence the propagation of waves in rotating plasmas