非线性衬底平板光波导TE模的图解法

本文推导出了以衬底光功率流为参数的非线性衬底光波导TE模的本征值方程,且采用简单的图解法求解。     

五层非线性平板波导TE模的特性

文章提出了分析中间层为非线性介质结构的五层平板波导TE模的解析方法,推导出了这种结构下普遍适用的色散关系式,给出了各层介质中的场分布和功率分布的解析式,并根据这一模型,就对称结构的五层非线性平板波导结构的模式特性进行了实例计算与讨论。     

三次谐波光子带隙谐振腔回旋管

分析了光子晶体谐振腔（PBGC）的模式选择功能,实现PBGC回旋管振荡器高阶电磁模与高次电子回旋模的有效耦合。通过对PBGC禁带特性的分析,定出了工作模式TE34模,并成功抑制了模式竞争。文中建立了PBGC回旋管的等效半径的概念,完成了自洽非线性理论和相关的计算机数值模拟程序。研究发现TE34模能有效地与电子的3次回旋谐波相互作用,其耦合频率为130.5GHz,并极大地降低了对工作磁场的要求。在考虑诸多物理因素影响的情况下,对该3次谐波PBGC回旋管振荡器进行了参数优化研究,得到了参数为：电压430kV、电流35A、磁场1.84T、输出功率1.75MW、互作用效率11.5%的3次谐波TE34模PBGC回旋管振荡器。     

用二维矢量FD—TD法分析平面光波导模场分布

本文用二维矢量时域有限差分（FD－TD）法分析了平面光波导基模（TE0模）和高阶模（TE1模）的模场分布情况,分析基模时用了5种不同形态的光谱作为激励,所得的光场分布在光场传播达到稳定后完全相同,所得TE0模和TE1模的二维稳态模场分布结果均与解析法讨论的结果一致。     

非线性平板波导中均匀芯区场的归一化形式

通过理论分析及典型实例计算，分析了包层及衬底均为非线性Kerr型介质、芯区为线性均匀介质的对称3层平板波导的TE0模出现均匀场分布的条件及其归一化形式。给出了自聚焦和自散焦情况下对称3层平板波导TE0模的归一化场分布曲线以及功率随归一化模折射率变化曲线。     

TE振荡模在含各向异性左手材料劈形平面波导中的传输

研究了含各向异性左手材料的劈形平面波导TE振荡模的传输特性.首先,从麦克斯韦方程组出发,得到该模的色散方程、反射系数方程、传输系数方程以及功率损耗方程.然后,根据这些方程画出了相关特性曲线并对这些曲线进行了仔细分析,研究发现:(1)当模阶数m=0,1,2时,TE模的有效折射率具有较大的值,且随着波导长度的增加而快速减小;(2)TEo模具有超大的反射系数,最大值接近0.967;(3)TEo模传输系数总是小于等于1.2×10-3;(4)当劈形波导斜率k=0.01时,其功率损耗大于等于0.998,而且,当频率为5.0 GHz时,功率损耗仍大于等于0.98.     

含单负材料对称三层平板波导的模式特性

由电磁场的波动方程和边界条件建立了单负材料作为芯层的对称三层平板波导的模式本征方程,用图解法研究其色散特性。研究发现,单负介质波导不支持快波的传播,只支持表面波的传播。在负磁材料平板波导中只存在TE表面模,不存在TM表面模。分析了在负磁材料平板波导中TE模受磁导率的比值-μ2／μ1和波导参数的影响,给出了横向场分布图。在-μ2/μ1〈1时,偶对称只有TE0表面模存在,奇对称只有TE1表面模存在,高阶模式并不存在,且两种模式都没有低频截止;-μ2/μ1〉1时,TE1表面模始终不出现;TE0模的存在与否和波导参数有关,在一定条件下TE0模可出现双模并存。给出的结果可望对表面波器件的设计提供理论基础。     

1.3μmInGaAsP-In P隐埋异质结构激光器改进线性的标准

<正> 平面有源区隐埋异质结(BH)激光器光-电流特性的非线性与高阶模变换、光谱展宽有关,在某些情况下还与 TM 偏振受激发射的开始有关。该文介绍了测量和计算的情况并指出,在减小了有源体积的器件中,在较高的功率下出现这些非线性。这些结果对于用在高比特速     

用于TE_（01）圆电模毫米波水负载大功率计的研制

针对回旋行波管输出的高阶圆电模式TE01模,本文开展了一种新型大功率辐射式水负载的研制工作,其研制的主要技术难点有：适用于高阶圆电模式、大功率容量、低驻波系数的实现和水密封性等,成功研制出了一种由石英玻璃烧制的特殊结构Ka波段大功率辐射式圆波导水负载,其具有功率容量大、频带宽、体积小、重量轻、结构紧凑等优点,并已成功应用于回旋行波管的功率测试系统。实验结果表明,其相对频率带宽大于15%,带内电压驻波比小于1.2,峰值功率容量大于150kW,平均功率容量大于5 kW。     

一种X波段GW级TE21模耦合器的设计

针对目前高功率微波(HPM)传输与发射系统无法实现自跟踪的问题,引入TE21模耦合器,使HPM系统具备自跟踪能力。由于现有的TE21模耦合器应用到HPM中会面临功率容量的问题,为此设计一种X波段GW级TE21模耦合器,以探索其在HPM系统中的应用。仿真结果表明：设计的TE21模耦合器在9.0~10.0 GHz频率范围内,对TE21模的耦合度大于-0.5 dB,对TE11模的耦合度小于-40 dB,功率容量可达到GW量级。     

Modulation instability in negative refractive materials with saturable nonlinearity

Starting directly from the nonlinear propagation equation including saturable nonlinearity, the first-and the second-order nonlinear dispersions, the dispersion relation, instable condition, gain spectra, and the dimensionless cut-off frequency and gain spectra of modulation instability (MI) in the negative refractive material are deduced by adopting the linear stability analysis and Drude electromagnetic model. And the variations of the dimensionless gain spectra with the normalized angular frequency and normalized incident power are calculated and discussed for different sign relations between the linear dispersion and the third-order nonlinear coefficients. The results show that in the negative refractive index region, MI can occur irrespective of the sign relation between the linear dispersion and the third-order nonlinear coefficients. And depending on different dimensionless angular frequencies and different sign relations, the variations of the dimensionless gain spectra with incident power take on several different forms. Namely, the peak gain and the cut-off frequency of MI may increase then decrease with the increase of the incident power, or decrease monotonously. Moreover, MI may even have a threshold incident power for some cases.     

TM waves in nonlinear saturable thin films: a multilayered approach

The dispersion of guided TM (transverse magnetic)-polarized waves in a thin nonlinear saturable film bounded by linear media is investigated. The film is assumed to be isotropic with both of the electric field components contributing to its dielectric function. The variation of the wave effective index with the guided power and also with the surface magnetic field intensity is obtained. Different mechanisms giving rise to the nonlinearity of the film are shown to result only in small quantitative differences in the dispersion behavior. A recursive scheme for solving the nonlinear wave equation within the film is fully described. The scheme relates to the saturable dielectric function used and its based on the stratification of the film region into a large number of linear sublayers     

Ultrashort pulse propagation, pulse breakup, and fundamental soliton formation in a single-mode optical fiber

The propagation of ultrashort (0.83 ps), intense dye laser pulses through a single-mode optical fiber is investigated. The input wavelength is tuned in the vicinity of the zero dispersion wavelength of the fiber. Although the input power is sufficient to generate solitons of up to the tenth order we do not observe the formation of high-order solitons. Instead, the input pulse breaks up temporally and spectrally after an initial stage of narrowing, and an ultrashort Stokes pulse is formed which shifts continuously to lower frequencies with increasing fiber length. The parameters of this pulse closely correspond to those of the fundamental soliton solution of the nonlinear Schroedinger equation. Using fiber lengths from a few meters up to 1 km the resulting pulse durations lie between 55 and 410 fs and the corresponding wavelengths between 1.36 and 1.54 μm. Numerical simulations solving a modified nonlinear Schroedinger equation including higher order dispersion and the Raman effect are in good agreement with the experimental results. It is shown that the principal soliton pulse shaping mechanisms are pulse narrowing and the soliton self-frequency shift.     

高阶色散下饱和非线性负折射介质中的调制不稳定性

直接从负折射介质中包含高阶色散及饱和非线性效应的扩展非线性传输方程出发,采用线性稳定性分析法和德鲁德电磁模式,导出了调制不稳定性的色散关系和增益谱公式。考虑到今后的实验验证,以实际单位的形式计算了方程系数随归一化角频率的变化规律。再以实际单位的形式计算并讨论了增益谱随归一化角频率和归一化入射光强的变化关系。结果表明,当归一化角频率固定时,截止频率及峰值增益都随归一化入射光强的增加先增加后减少,归一化角频率不同,截止频率及峰值增益也不同,在靠近禁带处,增益谱远离零点。当归一化入射光强固定时,截止频率及峰值增益随归一化角频率的增加而增加,当归一化角频率增大到靠近禁带时,增益谱由紧挨零点变成远离零点。     

三层介质波导中TE波的转移矩阵及场分布研究

从TE波的波动方程出发,根据电磁场的边界条件,推导出了三层介质平板波导中电场的表达式,得到了波导层TE波的转移矩阵和模式本征方程,并计算出了光波的功率流密度分布,通过对传输功率流的分析得到:在平板介质波导中,传输电磁能量的厚度大于薄膜的实际厚度.最后用Matlab描绘的本征值图对场分布进行了研究,从图中得到:在对称平板波导中没有截止厚度和截止频率,而非对称平板波导中存在截止厚度和截止频率,薄膜厚度越大,能承载的导模数越多.     

五阶非线性色散缓变光纤负色散区的交叉相位调制非稳

推导了三、五阶非线性共存时有损耗单模色散缓变光纤中同偏振、不同波长的两光波的交叉相位调制不稳定条件和增益谱。在色散缓变光纤负色散区,详细分析了五阶非线性系数、色散纵向变化参量、两扰动的频率大小关系对交叉相位调制不稳定条件和增益谱的综合影响。结果表明,正、负五阶非线性分别对交叉相位调制不稳定性起加强和抑制的作用;两扰动频率大小关系不同,色散纵向参量的变化对调制不稳定增益谱的影响也不同;随参数的不同,增益谱存在有截止频率和无截止频率2种形状。     

自聚焦介质波导中的新型导波

本文给出了导波层为自聚焦介质平板波导波方程的特殊精确解,得到了具有非线性导波层的波导归一化色散方程及场分布,并对得出的结果进行了讨论。     

手征负折射率包层光纤的模式特性研究

对手征负折射率包层光纤的导模和表面波模的特性进行了理论研究,导出了模式特征方程,给出了3种不同参数情形下的模式的色散曲线、能流分布和归一化功率随归一化频率的变化关系曲线,并且与负折射率介质光纤和一般手征光纤的模式特性进行了比较.结果发现,其存在两个单模区,在某些频段,表面波模的能流和功率在一般介质的纤芯内为负而在手征负...     

Exact analytic solutions to the nonlinear wave equation for asaturable Kerr-like medium: modes of nonlinear optical waveguides andcouplers

Exact analytic solutions to the nonlinear wave equation for a lossless saturable Kerr-like medium are found. The nonlinearity is an intensity-dependent refractive index which saturates according to the model n²=n₀²±a|E|²/(1+b|E| ²). The solutions to the wave equation are used to determine the TE power-dependent dispersion relations, and therefore the guided modes, of a single waveguide structure and of a directional coupler whose coupling medium is the nonlinear saturable material. Although the interaction between the sinh- and cosh-like modes of the coupler, and therefore the coupling length, is not treated in this work, it is shown that the critical power, defined in the literature to be the level of input power above which 100% of the power cannot be switched between the guides of a coupler, is a mathematical misinterpretation in both saturable media as well as in nonsaturable Kerr media. The absence of a critical power in single waveguide structures is also demonstrated. Parameters of GaAs-based waveguides and of a GaAs-GaAlAs MQW coupling medium are used in the numerical analysis     

高阶色散对光孤子及孤子对传输的影响分析

为了研究高阶色散对光孤子及孤子对传输的影响,采用分步傅里叶变换方法,对含高阶色散效应与不考虑高阶色散情况下的光孤子非线性薛定谔方程进行了数值求解,得到了孤子脉冲形状与色散阶数有着相关性这一结果.结果表明,奇数阶色散效应会使孤子及孤子对脉冲发生单边振荡,产生能量损耗,并在振荡侧产生次脉冲,而偶数阶色散效应会使孤子及孤子对脉冲发生明显的脉宽展宽,高阶色散效应对孤子脉冲的影响随阶数的增加而减弱.