Influence of group—velocity mismatch on soliton switching in a nonlinear fibre coupler

In this work, the influence of group-velocity mismatch on soliton self-routing pulse switching in a nonlinear fibre coupler is discussed in detail by the use of both variational approach and numerical simulation. The results obtained show that the group-velocity mismatch leads to the relative displacement between the two orthogonal polarization modes, increase of the critical power, and reduction of the elimination-light ratio. For sub-ps pulse, the influence cannot be neglected.     

The influence of hydrogen chloride doping level on the complex refractive indices of anisotropic polyaniline film: Application of a new internal reflection waveguide coupling technique

Nondestructive three‐dimensional refractive‐index measurements are used for the determination of both crystallinity and orientation in thin polymer films. The prism waveguide coupler is particularly suitable for three‐dimensional isotropic and anisotropic thin‐film studies because of the quantitative character of the information obtained and the ease of data acquisition. It has been limited, however, to measuring the refractive index of optically transparent or weakly absorbing films. This study shows that a modified prism waveguide coupler can be used to determine the complex refractive index over a range from transparent to highly absorbing films from the internally reflected light intensity. Thus, both the refractive index, n, and the extinction coefficient, k, can be obtained. This method is used to determine the anisotropic three‐dimensional n and k values of spin‐coated emeraldine base and hydrogen chloride doped emeraldine salt polyaniline films. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2481–2490, 2001     

Microscopic study of polymorphism of a photographic coupler

Polymorphism and polymorphic transformation of a photographic coupler have been examined using hot stage optical microscopy (HSOM). Two different polymorphs, metastable needle-like crystals and stable cubic-like crystals, were identified on heating. A solid-state transformation was found to occur from the metastable form to the stable form. Both polymorphs can precipitate from coupler solutions. The needle-like crystals appear in all cases examined; the cubic-like crystals precipitate only with higher concentrations and lower cooling rates. The solution-mediated transformation occurs in an organic solvent through dissolution of the metastable polymorph and growth of the stable polymorph. The growth rate of the stable polymorph is dependent on temperature as well as concentration. The activation energy of the growth is estimated for coupler solutions with different concentrations.     

数码摄影中的化学

数码摄影已成为人们日常生活的一部分。在阐明数码摄影原理的基础上,着重介绍了数码相片冲印过程中一些重要的化学反应,以凸显化学在数码摄影中的作用。     

DIAR黄成色剂的合成

DIAR黄成色剂的合成;DIAR成色剂;异丙氨基苯硫酚;固体光气     

DAR黄成色剂的合成

本文以α-新戊酰基-2-氯-5-[3-(2,4-二特戊基苯氧基)丁酰胺基]乙酰苯胺为母体,以2,5-二巯基-1,3,4-噻二唑为吸附基团,分别以1-甲酰基-2-(4-氨基)苯肼,1-乙酰基-2-(4-氨基)苯肼和1-三氟乙酰基-2-(4氨基)苯肼为增强基团合成了3种DAR黄成色剂.并通过IR,¹HNMR,MS确证了它们的结构.     

基于3×3平行排列耦合器的全光光开关的特性分析

提出了一种新型的基于3×3平行排列耦合器的全光光开关。此种光开关具有两个独立的输出端口且具有极好的偏振稳定性,消光比可达20dB。介绍了其工作原理,详细分析了信号光强度、控制光强度、光纤长度及耦合器分光比偏差等因素对各端口消光比的影响。比较了不同种类和长度光纤环的开关性能,首次得到了耦合器分光比偏差对消光比的影响曲线。     

基于夹层结构的偏振无关1×2定向耦合型解复用器的设计

提出一种基于夹层结构的偏振无关1×2定向耦合型解复用器,用于分离1310 nm和1550 nm两个波长.通过合理选择夹层结构芯区的折射率及波导间隙,可以调节同一波长两个正交偏振模的耦合长度相等,实现偏振无关;通过合理选择夹层结构波导宽度,可以使两个波长分别从不同输出波导端口输出,实现解复用功能.运用三维有限时域差分法进...     

光子晶体波导定向耦合器

在完整二维光子晶体中引入线缺陷后，就形成了光子晶体波导；将时域有限差分方法(FDTD)用于光子晶体波导耦合研究，计算了不同耦合长度情形下的波导各个出口处的透过率，结果表明：光子晶体波导耦合遵循普通介质波导耦合的一般规律，也有定向耦合的功能。进一步的研究表明：对于不同的频率，光子晶体定向耦合器耦合系数是不同的，并且耦合系数和对应的频率之间近似直线关系。     

Numerical analysis for millimeter wave slot type coupler

The numerical analysis for millimeter wave slot type coupler of overmode waveguide cavity is studied by mode-matching taking account of the thickness of the plate on which the slot is cut. It is found that the higher modes in cavity can be suppressed by proper thickness of the plat and proper dimension of the output waveguide.