共查询到20条相似文献,搜索用时 125 毫秒
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报道了中心对称光折变晶体与线性电介质界面表面波的形成及能量变化. 通过调节传播常数和波导参数的方法,可以得到非局域、振荡、局域三种类型的表面波. 波导参数和传播常数之差大于阈值时,线性电介质和中心对称光折变晶体界面可以形成局域表面波. 波导参数为正值时,局域表面波主要聚集在中心对称光折变晶体内,随着传播常数的增大,波能量随之单调递增,表面波可以稳定传播. 在给定的条件下,调节决定非线性作用强度的可变参量可以控制局域表面波模的阶数和传播波形.
关键词:
非线性光学
中心对称光折变晶体
表面波 相似文献
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一维受限反铁磁光子晶体的性质 总被引:4,自引:0,他引:4
采用传输矩阵法计算了一维受限反铁磁光子晶体的带结构和透射比.研究结果表明:除来源于结构周期性的光子带隙外,体系还存在一种频率带隙,与反铁磁材料的共振性质以及受限尺寸有关.适当调节反铁磁各向异性轴的方向和受限尺寸,在反铁磁共振频率处可以出现比大块反铁磁材料的带隙宽约15倍的频率带隙.一定条件下,在大块反铁磁材料带隙的频率区间上,一些电磁波模式是可以在受限光子晶体中传播的.最后分析了几种典型的透射谱,与带结构吻合. 相似文献
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本文用微扰理论导出了横向磁化条件下铁磁薄膜中非线性静磁表面波满足的运动方程和它的解析解。获得非线性色散关系,揭示了传播功率致使静磁表面波频带压缩。研究了群色散和非线性频移随频率和薄膜厚度的变化规律。证明了横向磁化时非线性MSSW不能以静磁孤子的形式存在。
关键词: 相似文献
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利用非线性传递矩阵方法研究了Voigt位型下电介质/反铁磁/电介质 结构二次谐波生成的非倒易性. 研究发现外加静磁场反向和电介质层排序翻转均对二次谐波输出产生影响, 出现了二次谐波生成的非倒易性. 二次谐波生成非倒易性频率区域在反铁磁共振区, 此区间正处于THz频段. 随着入射角度的增加, 非倒易性的效果越来越明显. 研究二次谐波生成的非倒易性, 可为反铁磁器件的设计加工提供理论支持. 相似文献
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左手系材料界面上的非线性TE电磁波 总被引:4,自引:4,他引:0
针对电磁波在非线性左手系材料中的传播性质, 分别研究了左、右手系材料界面以及两左手系材料界面上非线性TE表面波的传播行为讨论了导波的频率特性、色散关系以及群速度随频率的变化规律分析表明,两种界面上的非线性TE表面波均存在频率通带和禁带,且带宽是传播功率的函数揭示了在一定条件下,左、右手系材料界面上既可以支持正向传播的非线性TE表面波,也可以支持反向传播的非线性TE表面波;两左手系材料界面上表面波的传播性质因材料参量的变化差异较大,一定参量条件下,该界面上仅支持反向传播的非线性TE表面波. 相似文献
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《低温物理学报》2016,(5)
晶体的物理性质可以通过晶体掺杂的方式来改变.因此,在这工作中,我们研究了Br掺杂效应对(CH_3)_2NH_2Cu(Cl_(1-x)Br_x)_3(0≤x≤1)晶体的结构,物理性质及比热的影响.研究表明,晶体结构几乎不受Br掺杂影响,而温度T2K的磁性质,其随掺杂浓度的变化而变化.掺杂浓度从x=0到x=1变化过程中,磁相互作用从顺磁态变为铁磁态.这现象可理解为随着掺杂浓度增大,最近邻磁性离子间相互作用发生改变,导致x=0晶体的磁结构中反铁磁二聚化解体.不同磁场下x=0和x=1掺杂的晶体比热研究,x=1晶体的磁比热在温度2-4.5K区域呈现出一个随磁场变化的"肩",表明存在于x=0晶体中的自发反铁磁有序相和磁场诱导有序相被抑制.综上所述,磁性质和比热特征均表明掺杂能有效改变物理性质:x=0晶体的磁结构中反铁磁二聚化解体,x=1掺杂的磁结构演变成铁磁二聚化的反铁磁链. 相似文献
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随着110 GHz高功率太赫兹波功率容量的提升,其引起的大气击穿问题越来越受到重视。将若干等效电离参数表达式引入到电子雪崩密度方程中,计算了不同压强下的大气击穿阈值。结果表明,由Ali等效电离参数得到的110 GHz击穿阈值与实验数据符合得很好。在此基础上,利用Ali等效电离参数对逃逸传输能量密度与太赫兹波振幅的关系进行了分析。结果表明,当太赫兹波振幅小于击穿阈值时,逃逸传输能量密度随功率密度的增加线性增加;当太赫兹波振幅大于击穿阈值时,逃逸传输能量密度随功率密度先减小后增大。 相似文献
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V. V. Tikhonov S. A. Nikitov 《Bulletin of the Russian Academy of Sciences: Physics》2017,81(8):969-977
The effects of parametric magnon–phonon instability and the self-modulation of magnetostatic and fast magnetoelastic waves are revealed. It is found that instabilities are caused by the decay of the initial waves stimulated by high-Q acoustic resonances. Decays of the first and the second order (three- and four-magnon–phonon decays) are observed. Their characteristics and existing conditions are determined. Magnetostatic wave decays have both upper and lower thresholds. It is shown that magnetoelastic waves become stable above the upper thresholds. The existence of the upper threshold is due to several competing decay scenarios. 相似文献
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《Physics letters. A》2020,384(24):126451
In this paper, we explore transverse electric surface waves propagating along the crystal with jump change of Kerr nonlinearity in dependence on field amplitude. The dielectric permittivity in the proposed model of nonlinearity is characterized by abruptly changing unperturbed dielectric constant and Kerr nonlinearity coefficient from one value to another when field amplitude exceeds the threshold value of the switching field. This allows to find exact solutions of model equations in different cases of nonlinearity signs, and to obtain the dependence of wave characteristics, including total power flux, on effective refractive index in explicit form. Such solutions describe two new types of nonlinear surface waves with specific structure depending on electric field amplitude. We derive the conditions of surface domain formation. It is found that the largest percentage of radiation is concentrated within the domain. 相似文献
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On the stability of capillary waves on the surface of a charged jet moving relative to the environment 总被引:1,自引:0,他引:1
A dispersion relation is derived for capillary waves with arbitrary symmetry (arbitrary azimuthal numbers) on the surface
of a charged cylindrical jet of an ideal incompressible conducting liquid moving relative to an ideal incompressible dielectric
medium. It is shown that a tangential discontinuity in the velocity field on the surface of the jet leads to periodic instability
of waves (similar to the Kelvin-Helmholtz instability) at the interface and destabilizes both axisymmetric and flexural waves.
The wavenumber range for unstable waves and the instability growth rate increase with the field strength and relative speed
of motion, varying as the square of these parameters. In the case of the neutral jet, the flexural instability is of the threshold
character and sets in starting from a certain finite value of the speed rather than at an arbitrary small speed. 相似文献
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Yu. V. Gulyaev P. E. Zil’berman A. V. Lugovskoi 《Journal of Experimental and Theoretical Physics》1997,84(1):109-119
The equations of motion for the slowly varying complex amplitudes of spin waves parametrically excited by a localized pumping
magnetic field have been derived. A solution of these equations satisfying given boundary and initial conditions has been
obtained. The energy dissipated by spin waves decreases with the pumping intensity beyond a certain pumping power, which can
be termed the regeneration threshold. The losses vanish and change sign at the instability threshold. Both thresholds depend
heavily on the linear dimension L of the pumping zone, increasing with decreasing L. Owing to the regeneration process, the dissipation length of spin waves increases without bound as the pumping power approaches
the instability threshold. Consequently, perturbations of a uniform state due to the boundary penetrate throughout the pumping
zone, regardless of the dimension L. As a result, the full pattern of parametric instability is strongly affected by the zone boundary: 1) the spatial distribution
of wave amplitudes becomes nonuniform everywhere inside the zone; 2) the amplitude growth rate in the unstable regime decreases
at all points when perturbations due to the boundary reach these points; 3) the instability threshold is independent of the
spin-wave frequency offset from the parametric resonance frequency. The calculated minimum instability threshold as a function
of the bias magnetic field (the “butterfly” curve) changes shape with L, in agreement with the available experimental data.
Zh. éksp. Teor. Fiz. 111, 199–219 (January 1997) 相似文献
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The TM-polarized waves propagating along the interface between a nonlinear Kerr-like material and linear cladding are investigated. We analyse the nonlinear dielectric permittivity as a function of the electromagnetic field. It is shown that an exact analytical solution of Maxwell's equations corresponding to the TM surface polariton in the form described by sech function do exist in a Kerr-like nonlinear medium with the permittivity profile given by a hypergeometric function. We compare our analytical solution and analogous exact numerical solution in a Kerr medium. The power flow down the interface between two media is also discussed. 相似文献
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Some factors that may affect human perception thresholds of the vertical whole-body vibrations were investigated in two laboratory experiments with recumbent subjects. In the first experiment, the effects of gender and age of subjects on perception were investigated with three groups of 12 subjects, i.e., young males, young females and old males. For continuous sinusoidal vibrations at 2, 4, 8, 16, 31.5 and 63 Hz, there were no significant differences in the perception thresholds between male and female subjects, while the thresholds of young subjects tended to be significantly lower than the thresholds of old subjects. In the second experiment, the effect of vibration duration was investigated by using sinusoidal vibrations, at the same frequencies as above, modulated by the Hanning windows with different lengths (i.e., 0.5, 1.0, 2.0 and 4.0 s) for 12 subjects. It was found that the peak acceleration at the threshold tended to decrease with increasing duration of vibration. The perception thresholds were also evaluated by the running root-mean-square (rms) acceleration and the fourth power acceleration method defined in the current standards. The differences in the threshold of the transient vibrations for different durations were less with the fourth power acceleration method. Additionally, the effect of the integration time on the threshold was investigated for the running rms acceleration and the fourth power acceleration. It was found that the integration time that yielded less differences in the threshold of vibrations for different durations depended on the frequency of vibration. 相似文献
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The effect of unidirectional propagation of surface electromagnetic waves on the interface between an isotropic Faraday medium
and isotropic optically inactive medium is predicted. Such waves can be excited when the intensity of an external magnetic
field exceeds a certain threshold. Solutions to the dispersion relation are analyzed, and existence conditions for the surface
waves are established. 相似文献
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Radiation of elastic waves is studied that is emitted by a point load that crosses the interface of two elastic half-planes. It is assumed that the load has a constant magnitude, moves along a straight line normal to the interface, and has a constant speed that is smaller than the minimum shear wave speed in the half-planes. In this case the mechanism of excitation of elastic waves is conventionally referred to as transition radiation. The adopted model allows to obtain an analytical expression for the elastic field excited by the load in the frequency-wavenumber domain. Using this expression, the energy of transition radiation is derived in a closed form. It is shown that transition radiation of the body waves occurs at any non-zero velocity of the load. Additionally, transition radiation of interface waves may occur provided that parameters of the half-planes allow existence of Stoneley waves. A parametric analysis of the directivity diagram of radiated body waves is accomplished focusing on dependence of the diagram on the load speed, load direction, and parameters of the half-planes. Using parameters that allow radiation of interface waves, the energy of this radiation is compared to that of the body waves. It is shown that the energy of the interface waves is greater unless the load velocity is close to the lowest body wave velocity. 相似文献