Rigorous Analysis of Electromagnetic Wave Propagation in Cylindrical Dielectric Waveguide Array

Cylindrical Dielectric Waveguide Array(CDWA) should be considered as a kind of two-dimensionally periodic(2DP) medium. Based on the established rigorous theory for 2DP medium, a great amount of numerical results for CDWA were presented. Wave propagation in CDWA was analyzed in detail in this paper. Firstly, given the longitudinal wave vector (k _z=0), Brillouin dispersion relations between transverse wave vectors were analyzed when modulation coefficients or the rate of different dielectric areas in a unit cell varied. Interactions between space harmonics were also studied. Secondly, when the area of dielectric cylinder in the unit cell varied within a given range, CDWA dispersion relations were compared with Rectangle Dielectric Waveguide Array's, some interesting conclusions were obtained.     

SiO2波导布拉格器件中声表面波及声光相互作用分析

针对SiO2光波导声光布拉格器件,计算了SiO2非对称平板波导TE模式的横向场分布;给出了SiO2/ZnO/Air层状介质结构的性能方程、运动方程和麦克斯韦方程,推导出这种层状结构的特征方程,并结合所满足的边界条件,得到了各层介质的位移及电磁场分布;计算了声表面波所引起的光学相对介质隔离率张量的变化,最后讨论了声光衍射效率和光场与声场的重叠积分、声功率、声频率、声孔径和光波导参数之间的关系。结果表明,在低频范围内光场与声表面波场重叠良好;低阶模的重叠积分始终大于高阶模重叠积分,最低阶模与声表面波相互作用最强,所需声功率最小;当声功率一定时,增加声孔径可以提高衍射效率。     

The Sound Field in a Marine Waveguide with a Cylindrical Inhomogeneity

Acoustical Physics - A three-dimensional analytical solution is constructed for the model of an inhomogeneous hydroacoustic waveguide with a cylindrical inhomogeneity within the sedimentary layer....     

Analysis of Forced Vibrations in a Functionally Gradient Cylindrical Waveguide

Acoustical Physics - Wave propagation that occurs in a prestressed cylindrical waveguide with inhomogeneity along the radial coordinate under a periodic radial load concentrated in a ring-shaped...     

On Estimating the Laws of Radial Inhomogeneity in a Cylindrical Waveguide

Acoustical Physics - The inverse problem about reconstruction of a function characterizing the variation of the elastic modulus in an inhomogeneous cylindrical waveguide according to information...     

Relativistic Electromagnetic Solitary Wave in a Cylindrical Magnetized Plasma

In the presence of an applied static and uniform magnetic field, a cylindrical Kadomtsev-Petviashivili equation is derived for a relativistic electromagnetic solitary wave propagating in collisionless plasma consisting electrons, positrons, and ions in the case of weak relativistic limit. This equation is solved in a stationary frame to obtain explicit expression for the velocity, amplitude and width of solitons. The amplitude of the solitary wave has a maximum value at a critical αc of the ratio of the ion equilibrium density to the electron one, and it increases as the applied magnetic field becomes larger.     

Wave Propagation Along a Helical Step-Loaded Groove Waveguide

A new kind of helical groove structure, step-loaded groove waveguide is presented and analyzed in this paper. The dispersion equation of this structure is derived by means of a field-matching method. This equation may be reduced to the dispersion equation of helical ridge-loaded structure and rectangular one. In order to demonstrate the influence of the step on the dispersion properties, the comparison of the dispersion characteristics is made in these helical rectangular and modified rectangular groove structures. Form the analysis, it is shown that the step loading tends to reduce the dispersion of the helical groove circuit and the step-loaded structure has the weaker dispersion compared with the rectangular one or the ridge-loaded one. The effect of the step shape on the wave properties is also discussed under the deep groove case. The theoretical results explicitly indicate that the V-like step-loaded structure has the weakest dispersion in all step-loaded structures.     

A Second-Order Theory for Electron Plasma Solitary Waves in a Cylindrical Waveguide

To describe the long time asymptotic behaviour of weakly nonlinear plasma waves propagating in a strongly magnetized plasmafilled cylindrical waveguide the usual KDV equation which is first order in wave amplitude is extended to second order including the effects of finite temperature, mobile ions and giving a proper treatment to the radial co-ordinate for all possible modes of propagation. The second-order effects on the first-order solitary wave profile, phase speed and first order correction to the wavelength are all determined and discussed.     

Cyclotron Wave-Particle Interactions in the Whistler-Mode Waveguide

We study the cyclotron interaction of energetic electrons and whistler waves in plasma waveguides formed by inhomogeneous distribution of cold plasma. Such waveguides can be formed in the Earth's magnetosphere, e.g., by the plasmapause or by ducts with enhanced background-plasma density. In this paper, we consider a cylindrically symmetric model of a magnetospheric duct with enhanced cold-plasma density in a homogeneous magnetic field. The spatial structure of the eigenmodes of such a waveguide is found. We obtain a set of self-consistent quasilinear equations for cyclotron instability with eigenmode structure taken into account, thus generalizing the quasilinear theory of a magnetospheric cyclotron maser.     

Linear Theory of Free Electron Laser with a Plasma-Loaded Cylindrical Waveguide

The dispersion characteristics of plasma–loaded free-electron laser has been analyzed using linear fluid model. The device under consideration consists of the cylindrical metallic waveguide, completely filled with background plasma and a relativistic electron beam which passes through a helical wiggler magnetic field. The result predicts that reasonable plasma density tends to improve the growth rate of the low-frequency optical wave of FEL and causes an shiftup in the operating frequency, However it has little effect on the growth rate of the high-frequency wave. In the plasma–loaded FEL, for the FEL oscillator, it may be tuned by varying the plasma density; and for the FEL amplifier, the wider frequency bandwidth is gained. A critical density n ^c _p for the background plasma density is found.     

Longitudinal Wave Propagation in Dielectric Waveguide Array

Based on the established rigorous theory for two-dimensionally periodic (2DP) medium, Longitudinal propagation in Dielectric Waveguide Array (DWA) was analyzed in detail. Firstly, given longitudinal wave vector (k _z), Brillouin dispersion relations between transversal wave vectors were analyzed. Interactions between space harmonics were also studied. Secondly, on condition that transversal wave vector k _x equaled k _y, dispersion relations between longitudinal and transversal wave vectors were analyzed in detail. Because of interactions between space harmonics increasingly getting stronger with k _z or modulation coefficients increasing, stop-bands could be distinctly displayed and thus longitudinal propagation in DWA could be comprehensively analyzed. The applications about longitudinal propagation in DWA were also discussed.     

三波非共线作用参变过程的相位匹配研究

对各向异性单轴和双轴非线性晶体中三波非共线作用参变过程的相位匹配进行了详细的研究，给出了参变光在非线性晶体主平面内传播的所有非共线参变过程可能的相位匹配类型和相位匹配条件，并推出了所有可能的非共红参变过程的临界相位匹配解的解析表达式。     

Diffraction of Electromagnetic Waves by an Anisotropic Cylindrical Inhomogeneity in a Planar Waveguide

We consider diffraction of electromagnetic waves by an anisotropic cylindrical inhomogeneity located in a planar waveguide with perfectly conducting walls. Anisotropy is allowed for by using the uniaxial-crystal approximation. A rigorous analytical solution is represented in the form of double sums over eigenfunctions of a planar waveguide with perfectly conducting walls and azimuthal eigenfunctions of a cylinder. Different components of the intensity of the electric field scatttered by an anisotropic inhomogeneity are numerically calculated. The influence of the anisotropy and sizes of the inhomogeneity on the scattered field is analyzed. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 7, pp. 605–615, July 2005.     

Eigenwave Spectra of an Anisotropic Cylindrical Solid-State Waveguide

Technical Physics - Dispersion properties of eigenwaves of an anisotropic cylindrical solid-state waveguide without frequency dispersion in permittivity tensor components have been analyzed...     

光波导振荡场传感器

针对消逝场传感器的不足,提出了一种传感介质处于波导芯层,且以超高阶导模为探针的光波导振荡场传感器.由于其波导芯层处于功率密度极高的振荡场区域,而超高阶导模又具有对芯层参数极为灵敏的性质,因此这种新型传感器的灵敏度大大增强.实现了超越消逝场传感器灵敏度极限值几个量级的位移传感器.     

Talbot Effect in Three Waveguide Arrays

By taking the coupling between the non-neighbourhood waveguides into account, the coupling characteristic of three waveguide arrays is analysed. The strong coupling equation of three waveguides is dealt with Laplace transform and LU decomposition. The general field evolution equation is obtained by inversion of the Laplace transform. The results show that the self-imaging conditions （Talbot effect） do not satisfy in general. The theoretical predictions are in good agreement with the BPM simulations.     

On the Symmetrical Modes in a Cylindrical Nonisothermal Plasma Waveguide in a Finite External Magnetic Field

A MHD, symmetrical, nonpotential waves in nonuniform, cylindrical nonisothermal plasma waveguide placed in a finite external magnetic field H ₀ directed along the axis of the waveguide are considered. The thermal velocity of the electrons ν_Te = (kT_e/m_e)^1/2 (k — Boltzman's constant, T_e — temperature, m_e — mass of the electron) is not neglected. As a consequence we obtain one more solution in the plasma region and respectively an equation of third power on χ² — the transverse wave number. As far as we know only equations of second power on χ² describing non-potential waves are investigated. The dispersion equations are written solving the boundary-value problem. Our results coincide with well known ones when the electron thermal velocity tends to zero.     

Global Wave Solution of generalized MHD Equations in a Cylindrical Plasma

The linear eigenstate problem of generalized magnetohydrodynamics(MHD) equations in a cylindrical plasma is discussed. The effects of finite frequency and finite pressure perturbation lead to an important result: the resonant layer of the shear Alfven waves is not a singular layer. In this paper, the MHD equations are reduced to four differential equations of first order for perturbed quantities. An analytical dispersion relation for a homogeneous plasma cylinder is obtained. The K. Appert theory is a limiting case of our theory     

声波导管对圆柱型共鸣腔声场扰动的研究

声学共鸣法是目前测量流体热物性、热力学温度和玻尔兹曼常数最精确的方法之一,声波导管为共鸣腔提供声源和气体进入口,但是会破坏共鸣腔的理想表面从而导致腔体内气体介质共鸣频率的偏移(△f)和共鸣峰半宽的增加(g)。本文从一阶声学微扰出发建立了声波导管对共鸣腔声场的扰动模型,分析了导管位置、长度和半径大小对腔体中介质共振频率的影响。进一步测量了52～1763 mm之间六个不同长度的导管在T=332 K和p=50～500 kPa时,圆柱共鸣腔中轴向共鸣模式的共鸣频率和半宽的变化,测量结果与理论计算值吻合较好,证明了理论模型的正确性。