一种基于非线性光纤环镜开关特性的超短光孤子产生方法

提出了一种利用非线性光纤环镜的开关特性将连续波同时转化为亮孤子和暗孤子的新方法 ,即让连续波和另一波长的调制脉冲串共同耦合入光纤环镜 ,交叉相位调制使得一部分连续波被环镜透射 ,其余部分被反射 ;再让透射波和反射波分别在反常色散光纤和正常色散光纤中传输 ,自相位调制和群速度色散之间的相互作用使得透射波和反射波分别演化为亮、暗孤子。数值计算表明 ,该方法不仅可产生脉宽比调制脉冲窄、重复频率比调制脉冲高的亮孤子和暗孤子 ,而且几乎可将全部的连续波能量转化为孤子能量。     

Effect of dark soliton on the spectral evolution of bright soliton in a silicon-on-insulator waveguide

The spectral evolution of bright soliton in a silicon-on-insulator optical waveguide is numerically simulated using the split-step Fourier method. The power and input chirp of the dark soliton and the second-order dispersion are varied to investigate the effect of dark soliton on the spectrum of bright soliton. The simulations prove that the dark soliton modifies the spectral shape of the bright soliton. Further, the variation in the power of dark soliton affects the splitting of bright soliton. Furthermore, the chirped dark soliton can improve the spectral width and flatness. The variation in the dispersion of dark soliton modifies the phase matching of the bright soliton and the dispersive wave emission, thereby affecting the spectral evolution.     

Dipole-exchange spin wave spectrum in an anisotropic ferromagnetic waveguide with a rectangular cross section

A theory has been constructed that strictly describes the spectrum of dipole-exchange spin waves in an arbitrarily magnetized anisotropic ferrite waveguide with a rectangular cross section. The theory takes into account the spatial inhomogeneity of the internal magnetic field in the waveguide cross section. The influence of parameters of the ferrite waveguide on the distribution of the internal magnetic field in the waveguide cross section is analyzed. The dispersion characteristics of two waveguide types most widely used in practice are investigated. The dipole-exchange spin wave spectra calculated for a transversely magnetized waveguide are presented and the distributions of the dynamic magnetization in the waveguide cross section for several types of volume and localized spin-wave modes are constructed.     

Quantized spin excitations in a ferromagnetic microstrip from microwave photovoltage measurements

Quantized spin excitations in a single ferromagnetic microstrip have been measured using the microwave photovoltage technique. Several kinds of spin wave modes due to different contributions of the dipole-dipole and the exchange interactions are observed. Among them are a series of distinct dipole-exchange spin wave modes, which allow us to determine precisely the subtle spin boundary condition. A comprehensive picture for quantized spin excitations in a ferromagnet with finite size is thereby established. The dispersions of the quantized spin wave modes have two different branches separated by the saturation magnetization.     

BCVIG单晶的布里渊散射

用布里渊散射技术测量了BCVIG(Bi_3-2xCa_2xFe_5-xV_xO₁₂)单晶的磁振子散射谱,同Sande-rcock,Wettling对YIG以及刘玉龙等人对Bi-YIG单晶的测量相比,我们得到了除主峰之外的连续谱带。按照偶极-交换自旋波理论讨论了测到的自旋波谱。测量还表明BCVIG单晶的自旋波劲度系数D比YIG和Bi-YIG单晶大得多,讨论了D增大的原因,研究了D与入射激光功率的关系。 关键词：     

Dark solitons in ferromagnetic chains with first- and second-neighbor interactions

We present a study of the ferromagnetic spin chain with both first- and second-neighbor interactions. We obtain the condition for the appearance and stability of bright and dark solitons for arbitrary wave number in the Brillouin zone. The influence of the second-neighbor interaction and the anisotropy on the soliton properties is considered. The scattering of dark solitons from point defects in the discrete spin chain is investigated numerically.     

Linear and nonlinear spin wave resonances in a very thin amorphous wire

Linear and nonlinear FMR spectra of a very thin amorphous wire are investigated. A phenomena called “spin wave ripple” is reported here. It is observed on the low field side of the linear resonance curve and is attributed to the excitation of radial standing spin waves with the energy corresponding to the incident microwave frequency. The fine structure of the nonlinear resonance curves, recently observed on thin amorphous wires, is then explained by the dipole-exchange models of a cylinder parametrically excited by Suhl's first-order process. This explanation is consistent with the value of the exchange stiffness constant A determined from the spin wave ripple.     

非相干耦合的亮和暗光伏空间孤子对的偏转特性

采用数值方法研究了在一个具有扩散效应的光伏光折变晶体中的非相干耦合的亮和暗光伏空间孤子对的偏转特性.结果表明,由于非相干相互作用,晶体中的一个亮孤子和一个暗孤子互相俘获,且两个孤子的中心沿着相同的轨迹移动.发现,当亮孤子的入射峰值强度不变时,通过调节暗孤子的入射背景强度可以控制亮孤子的偏转;当暗孤子的入射背景强度处于一个特殊值时,亮孤子的偏转被抑制,而当暗孤子的入射背景强度偏离这个特殊值时,亮孤子发生偏转.同样,当暗孤子的入射背景强度不变时,其偏转可以通过调节亮孤子的入射峰值强度来控制.     

Observation of spin-wave envelope Dark solitons in ferromagnetic films

Microwave spin-wave envelope dark solitons were experimentally observed for the first time. Dark solitons with zero minimum amplitude were generated by two-frequency excitation of input spin waves with a fixed amplitude. Nonlinear interaction between these two traveling waves gave rise to periodic sequences of dark solitons in a ferromagnetic film.     

Exact soliton solution of spin chain with an external magnetic field in linear wave background

Employing a simple, straightforward Darboux transformation we construct exact N-soliton solution for anisotropic spin chain driven by an external magnetic field in linear wave background. As a special case the explicit one- and two-soliton solution dressed by the linear wave corresponding to magnon in quantum theory is obtained analytically and its property is discussed in detail. The dispersion law, effective soliton mass, and the energy of each soliton are investigated as well. Our result show that the stability criterion of soliton is related with anisotropic parameter and the amplitude of the linear wave.     

Observation of the chaotic spin-wave soliton trains in magnetic films

The transition from stationary to chaotic spin-wave soliton trains has been observed. The experiment utilized cw excitation of envelope solitons through self-modulation instability of spin waves. By increasing the spin-wave power, the secondary self-modulation instability succeeded the primary modulation instability, resulting in after-modulation of the soliton train amplitude. Further increase of the spin-wave power led to development of the higher-order instabilities, resulting in formation of the chaotic soliton train.     

增益色散及双光子吸收所支持的小幅孤波

通过连续波背景上的小幅近似，给出了光纤中增益色散及双光子吸收所支持的小幅暗孤波解，讨论了它们在参数空间中不同区域的演化特征，结果表明：在一些区域存在稳定的小振幅暗孤波，但在另一些区域，这种孤波是不稳定的。     

The microstructure of amorphous Co−P and Ni−P investigated with TEM and SAXS

The lowest order quantum corrections to the energy of a static soliton, of an easy plane spin chain, are calculated. The discreteness of the lattice of spins is shown to significantly effect the quantum corrections. However, if one uses a similar approximation to treat the spin wave dispersion relation, then the parameters which one extracts from the experimentally determined dispersion are such that the magnitude of the quantum corrections calculated in the continuum approximation are essentially exact.     

Multitweezers generation using dark soliton pulses and applications

Multi-dark soliton pulses have been successfully generated by using forward and backward pumping of the S-band erbium doped fiber in the fiber optic loop, where the Stimulated Brillouin Scattering (SBS) is a nonlinear interaction between pump fields with Stokes field through acoustic wave. Results obtained have shown that the dark soliton trains can be generated and configured as the multi-optical tweezers. The advantage is that the generated tweezers are in the form of dynamic tweezers, where they can transmit/transport via the soliton communication link. The single dark soliton is also experimentally generated by using the different fiber optic scheme. We have also theoretically shown that the dynamic tweezers can be controlled and tuned, which is available for trapping and transportation in the communication link via a wavelength router. The quantum states of the transported atoms/molecules by the dynamic tweezers can be performed by using the quantum processing unit incorporating in the system.     

Magnetic excitations in solids

This article presents a review of low to moderate frequency magnetic excitations, termed magnons or spin waves, in magnetically ordered materials. The emphasis is on intuitive behavior rather than analytical theory. Topics include spin waves, magnetostatic modes, dipole-exchange modes, surface anisotropy, dispersion properties, nonlinear effects, and relaxation. These phenomena are illustrated with experimental examples based on magnon light scattering results as well as conventional microwave techniques.     

非均匀光纤中暗孤子传输特性研究

由于变系数非线性Schrödinger方程的增益、色散和非线性项都是变化的, 根据方程这一特点可以研究光脉冲在非均匀光纤中的传输特性. 本文利用Hirota方法, 得到非线性Schrödinger方程的解析暗孤子解. 然后根据暗孤子解对暗孤子的传输特性进行讨论, 并且分析各个物理参量对暗孤子传输的影响. 经研究发现, 通过调节光纤的损耗、色散和非线性效应都能有效的控制暗孤子的传输, 从而提高非均匀光纤中的光脉冲传输质量. 此外, 本文还得到了所求解方程的解析双暗孤子解, 最后对两个暗孤子相互作用进行了探讨. 本文得到的结论有利于研究非均匀光纤中的孤子控制技术.     

Microscopic theory of dipole-exchange spin waves in magnetic multilayers

A microscopic model is employed to calculate the spectrum of dipole-exchange spin waves in multilayers in which thin ferromagnetic films are separated by non-magnetic spacers. Two configurations are considered: in one the films have magnetizations parallel to each other, in the other the magnetizations are antiparallel. The calculations extend a previous microscopic formalism that allows the calculation of the dipole-exchange spin wave spectrum in thin films. The results show the splitting of the frequency bands and the mode mixing caused by the dipolar interaction between the films as a function of spacer thickness.Received: 26 May 2004, Published online: 12 August 2004PACS: 75.30.Ds Spin waves - 75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.) - 75.70.-i Magnetic properties of thin films, surfaces, and interfaces     

Modulational instability of dark solitons in three wave resonant interaction

We study the propagation of velocity-locked dark triplet solitons in the three wave resonant interaction model. The modulational instability of the plane wave background where the solitons sit prevents the long range propagation. However even a small second order dispersion proves to greatly reduce, or suppress, the modulational instability gain, allowing for effective stable soliton propagation.     

Parallel pump spin wave instability in thin ferromagnetic films

The spin wave instability generated by parallel pumping in a tangentially magnetized ferromagnetic film is considered, with simultaneous regard for both the dipole and exchange fields. A dispersion equation and some expressions for the critical microwave threshold of the spin wave parametric excitation have been obtained. The dependence of the critical field on the magnetizing field has an unusually oscillating character. This is connected both with the discreteness of spin wave spectrum and the peculiarities of spin wave polarization in a tangentially magnetized film.     

Applicability of the Group Velocity Concept in Describing a Surface Spin Wave

The conditions under which a useful signal modulating a surface spin wave is not distorted and its propagation in a ferrite film can be characterized using the group velocity concept is studied. It is shown that the greater the ratio of the first and second derivatives of the dispersion dependence for the spin wave, the greater the distance this signal can pass without distortion. It is found that for a surface spin wave, the best conditions for the transmission of the useful signal are observed for a small region of wave numbers in the initial part of the wave spectrum, where this distance can be as great as several millimeters.