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1.
Cross-phase modulation instability in optical fibres with exponential saturable nonlinearity and high-order dispersion 下载免费PDF全文
Utilizing the linear-stability analysis, this paper
analytically investigates and calculates the condition and gain
spectra of cross-phase modulation instability in optical fibres in
the case of exponential saturable nonlinearity and high-order
dispersion. The results show that, the modulation instability
characteristics here are similar to those of conventional saturable
nonlinearity and Kerr nonlinearity. That is to say, when the
fourth-order dispersion has the same sign as that of the
second-order one, a new gain spectral region called the second one
which is far away from the zero point may appear. The existence of
the exponential saturable nonlinearity will make the spectral width
as well as the peak gain of every spectral region increase with the
input powers before decrease. Namely, for every spectral regime,
this may lead to a unique value of peak gain and spectral width for
two different input powers. In comparison with the case of
conventional saturable nonlinearity, however, when the other
parameters are the same, the variations of the spectral width and
the peak gain with the input powers will be faster in case of
exponential saturable nonlinearity. 相似文献
2.
高阶色散和指数饱和非线性光纤的调制不稳定性 总被引:1,自引:0,他引:1
采用线性稳定性分析法,解析和计算了指数饱和非线性和高阶色散光纤中的调制不稳定条件和增益谱。结果表明:当二阶和四阶色散同为负时,随着参数的不同,增益谱可能只有一个谱区,也可能出现两个分离的谱区;当二阶和四阶色散分别为正和负时,无调制不稳定性;在其它色散区,则只有一个谱区。指数饱和非线性可能使各谱区的谱宽、峰值增益随入纤功率的增大呈现出先增大后减小的特点,即出现两个不同的输入功率对应同一个不稳定增益峰值和谱宽的情形。在其它参数相同时,指数饱和非线性下增益谱的谱宽和峰值增益随入纤功率的变化速度将比传统饱和非线性更快。 相似文献
3.
Modulation instability in negative refractive metamaterials with exponential saturable nonlinearity and self-steepening effects 总被引:1,自引:0,他引:1
Modulation instability (MI) in negative refractive metamaterials with exponential saturable nonlinearity and the self-steeping effect is investigated by using the standard linear stability analysis and the Drude electromagnetic model. The dispersion relation, instability condition, cut-off frequency, gain spectrum, and their corresponding dimensionless expressions are analytically deduced and then calculated. The results show that, the self-steepening effect will suppress MI by decreasing the cut-off frequency and the maximum gain. And the larger the power density ratio is, more slowly the cut-off frequency and the maximum gain decrease with increase of the self-steepening parameter. Although the sign of the self-steepening parameter does not influence MI but its absolute value must be smaller than a certain value. Depending on different self-steepening parameters, the cut-off frequency and maximum gain may decrease or increase before decrease with increase of the power density ratio. In particular, for large self-steepening parameters, the power density ratio may have a threshold value. When the power density ratio is under this threshold, MI will disappear. 相似文献
4.
基于Drude模型研究了异向介质的色散磁导率对调制不稳定性的影响. 结果表明,在反常色散情形,赝五阶非线性在异向介质的负折射区中增大了调制频谱的范围及增益值,这与常规正折射介质中出现的现象正好相反;自陡峭效应在异向介质中有可能为负值,但无论正负,也无论在正折射区还是负折射区,它都抑制调制不稳定性的产生;二阶非线性色散效应在正、负折射区中分别促进和抑制调制不稳定性的产生. 在正常色散情形,由于二阶非线性色散效应的作用,使本来在常规正折射介质中不可能出现的调制不稳定性现象也能出现,这一特性为在正常色散区形成孤
关键词:
异向介质
调制不稳定性
色散磁导率
二阶非线性色散 相似文献
5.
基于Drude模型研究了异向介质的色散磁导率对调制不稳定性的影响. 结果表明,在反常色散情形,赝五阶非线性在异向介质的负折射区中增大了调制频谱的范围及增益值,这与常规正折射介质中出现的现象正好相反;自陡峭效应在异向介质中有可能为负值,但无论正负,也无论在正折射区还是负折射区,它都抑制调制不稳定性的产生;二阶非线性色散效应在正、负折射区中分别促进和抑制调制不稳定性的产生. 在正常色散情形,由于二阶非线性色散效应的作用,使本来在常规正折射介质中不可能出现的调制不稳定性现象也能出现,这一特性为在正常色散区形成孤 相似文献
6.
直接从异向介质中包含饱和非线性、自陡峭和二阶非线性色散效应的非线性扩展传输方程出发,采用线性稳定性分析法,导出了调制不稳定性的色散关系、不稳定条件、无量纲的临界扰动频率和增益谱。计算和讨论了异向介质正折射区无量纲的增益谱随归一化角频率和入射功率密度的变化关系。结果表明,在异向介质正折射区,随归一化角频率和入射功率密度的不同,增益谱将会出现扰动频率大于零、扰动频率大于某个非零临界值、扰动频率大于零而小于某个非零临界值3种形式。在归一化角频率较小时,调制不稳定性可能出现阈值入射功率密度;且在较小的入射功率密度时,调制不稳定性只能出现在大于某个临界频率时。 相似文献
7.
The linearized nonlinear propagation equation and its coefficients, gain spectrum of modulation instability (MI) in metamaterials (MMs) with fourth-order linear dispersion, second-order nonlinear dispersion, and three kinds of saturable nonlinearites, are analytically deduced by utilizing the linear stability analysis and Drude electromagnetic model. Then variations of gain spectra of MI with the normalized angular frequencies and the optical power densities are calculated in real units. In the negative refractive region, two kinds of gain spectra are discovered. The first (second) one is close to (far from) the zero perturbation frequencies and it corresponds to the lower (higher) normalized angular frequencies. Moreover, the second one has higher cutoff frequency, which is obviously beneficial to generation of high-repetition-rate pulse trains. While in the positive refractive region, only the first kind of gain spectra is found. With increase of the optical power densities, the peak gains and the spectral widths of MI increase before decrease, but they vary the most rapidly (slowly) for the exponential (conventional) saturable nonlinearities. The MI characteristics and their corresponding applications can be adjusted by several methods. 相似文献
8.
在非线性自散焦LiNbO_3∶Fe晶体中,实验观察了用激光作光源和用白光作光源两种情况下所产生的调制不稳定性,并从三个方面对这两种情况进行了比较。实验结果表明:在两种情况下,达到稳定状态前,MI现象都会随辐照时间的增加而变得越来越清晰,并且MI图样都会随着入射光束形状的变化而变化。不同的是,用白光作光源时,灯丝长度方向与晶体c轴方向的夹角大于等于45°时出现MI,而用激光作光源时,入射光束方向与c轴方向的夹角不大于45°才出现MI。 相似文献
9.
应用多光子非线性Compton散射模型和非线性薛定谔方程,研究了Compton散射对五阶非线性零色散附近调制不稳定性的影响.将入射光和Compton散射光作为产生调制不稳定性的机制,分析了光纤损耗、四阶色散和五阶非线性对增益谱的影响.结果表明:散射下的正或负五阶非线性分别使零色散附近的增益谱宽和峰值比散射前增大得更大或... 相似文献
10.
Effects of walk-off on cross-phase modulation induced modulation instability in an optical fibre with high-order dispersion 总被引:1,自引:0,他引:1 下载免费PDF全文
This paper investigates the effects of walk-off among optical pulses
on cross-phase modulation induced modulation instability in the
normal dispersion region of an optical fibre with high-order
dispersion. The results indicate that, in the case of high-order
dispersion, the walk-off effect takes on new characteristics and will
influence considerably the shape, position and especially the number
of the spectral regions of the gain spectra of modulation
instability.
Not only the group-velocity mismatch, but also the difference
of the third-order dispersion of two optical waves will alter the gain
spectra of modulation instability but in different ways. Depending on the
values of the walk-off parameters, the number of the spectral regions may
increase from two to at most four, and the spectral shape and position may
change too. 相似文献
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12.
In this paper, the modulation instability(MI), rogue waves(RWs) and conservation laws of the coupled higher-order nonlinear Schr?dinger equation are investigated. According to MI and the2?×?2 Lax pair, Darboux-dressing transformation with an asymptotic expansion method, the existence and properties of the one-, second-, and third-order RWs for the higher-order nonlinear Schr?dinger equation are constructed. In addition, the main characteristics of these solutions are discussed through some graphics, which are draw widespread attention in a variety of complex systems such as optics, Bose–Einstein condensates, capillary flow, superfluidity, fluid dynamics,and finance. In addition, infinitely-many conservation laws are established. 相似文献
13.
本文设计了一种基于超材料的偏振不敏感太赫兹宽带吸波体.吸波体包含两层金属和一层中间介质,表面金属层每一个周期单元由五种尺寸接近的金属块按照相邻不同的规律排列成5×5的方形阵列.各种尺寸金属块分别产生单峰谐振吸收,五个谐振吸收峰相互靠近从而产生宽带吸收.通过研究吸波体表面电流和电场z分量分布情况可知,入射太赫兹能量的吸收主要是由y方向上电场引起的电偶极子振荡和z方向上磁场引起的磁极化产生,而且金属层的欧姆损耗起主要作用.仿真结果表明,吸波体吸收率在80%以上的带宽约为1.2 THz,最高吸收率可达98.7%,半峰全宽(FWHM)为1.6 THz,该宽带吸波体的厚度约为中心波长的二十分之一,对偏振方向不敏感,且能实现大角度吸收,在太赫兹频段的电磁隐身、测辐射热探测器以及宽带通信等领域有潜在的应用价值. 相似文献
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15.
超常介质与常规光学介质的一个最重要的区别是前者具有色散磁导率,其折射率呈现出可正可负,这样调制不稳定性出现新特点。借助于Wigner变换,从一般的非线性薛定谔方程出发,得到了部分相干光满足Wigner-Moyal的方程,获得了色散关系和增益谱,揭示了部分相干度不仅可抑制调制不稳定性,而且还可以缩小发生不稳定性的频率范围。 相似文献
16.
17.
Ultra-broadband modulation instability gain characteristics in As_2S_3 and As_2Se_3 chalcogenide glass photonic crystal fiber 下载免费PDF全文
Based on the designed As_2Se_3 and As_2S_3 chalcogenide glass photonic crystal fiber(PCF) and the scalar nonlinear Schrdinger equation,the effects of pump power and wavelength on modulation instability(MI) gain are comprehensively studied in the abnormal dispersion regime of chalcogenide glass PCF.Owing to high Raman effect and high nonlinearity,ultra-broadband MI gain is obtained in chalcogenide glass PCF.By choosing the appropriate pump parameter,the MI gain bandwidth reaches 2738 nm for the As_2Se_3 glass PCF in the abnormal-dispersion region,while it is 1961 nm for the As_2S_3 glass PCF. 相似文献
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19.
We derive the dispersion equation for erbium doped fiber amplifiers (EDFAs), assuming the supplementary effects of time-derivative nonlinearities including intrapulse Raman scattering and self-steepening incorporated with third order dispersion and product of gain and square of dipole relaxation time parameter, in the extended form of nonlinear Schrödinger equation and investigate their impacts on gain and cut-off frequency of modulational instability (MI) in EDFAs. Also, the influences of those effects on instability of steady-state amplitude, in the form of generation of terahertz pulse train of femtosecond solitons from a weak-modulated signal by induced MI, are numerically simulated and discussed within EDFAs in normalized form. 相似文献
20.
We considered a high birefringence fiber ring cavity, which can be represented by a system of two incoherently coupled nonlinear Schrödinger equations with periodic boundary conditions. The stability of the system against time domain periodic perturbations could be strongly conditioned by fiber birefringence. We apply both a perturbative approach and a mean field approximation, in order to highlight the dependence of modulation instability on birefringence and ring detuning. We extend the study of the dynamical properties of the system by means of a phase matching interpretation and a selection of numerical solutions of the governing equations. 相似文献