双芯复合格点光子晶体光纤的负色散特性

介绍了一种双芯复合格点负色散光子晶体光纤,其包层是由连续电介质纯硅背景上挖出的两种大小不同的空气孔构成,芯区是由掺锗的高折射率的材料构成。为了实现负色散,还移去了包层中的一圈空气孔。采用频域有限差分法对其负色散特性进行分析表明,通过调整空气孔间距和两种空气孔的尺寸,可以得到不同程度的宽带负色散。当内芯半径取0.95μm,孔间距取2.15μm,大空气孔直径取1.9μm,小空气孔直径取1.1μm时,可在1.55μm处实现宽带负色散,其半峰全宽超过了200 nm。这种光纤的包层中空气孔呈六边形分布,空气孔的尺寸均大于1μm,降低了制作的难度。这种光纤可以用于波分复用光纤通信系统中的宽带色散补偿。     

非归零码在色散控制光纤链中的传输特性

以半极大全宽为20ps的高斯型光脉冲表示1码,用相应的各阶超高斯型光脉冲分别表示11、111、1111、11111、111111等码.在无损耗的三段色散补偿系统中,当路径平均色散为负、零及正,传输码率为17Gb/s时,讨论了脉冲的演变及脉冲间的相互作用,结果表明,在零和正平均色散下,11码和111码传输效果较差.文中对伪随机的64位码进行传输模拟,做出了传输后的眼图.计算说明负平均色散下传输效果最好.     

强色散补偿有耗光纤链中孤子的稳定传输

用平均近似的方法,得到了孤子在强色散有耗光纤链中演化的相图.在分析相图的基础上,提出了一个可使孤子保持稳定传输的新相图.按照这个新相图,给出了孤子稳定传输的参量.这些参量,通过数值运算,在我们感兴趣的区域里得到了验证.     

Modified surface plasmonic waveguide formed by nanometric parallel lines

In this paper, two kinds of modified surface plasmonic waveguides formed by nanometric parallel lines are proposed. The finite-difference frequency-domain method is used to study propagation properties of the fundamental mode supported by these surface plasmonic waveguide structures. Results show that the transverse magnetic field of the fundamental mode is mainly distributed in the face to face region formed by two rods. With the same geometrical parameters and the same working wavelength of 632.8~nm, in the case of rods with a triangular cross-section, the degree of localization of field is strong, i.e. the mode area is small, but the fraction of the modal power in the metal increases, so the effective index increases and the propagation length of the mode decreases. With the same geometrical parameters, relative to the case of a working wavelength of 632.8~nm, when working wavelength is large, the mode area of transverse magnetic field distribution is large, i.e. the degree of localization of field is weak, and the interaction of field and silver is weak too, then the effective index decreases, so the propagation length increases. The rounded radii of rods have a great influence on the performance of the surface plasmonic waveguides with rounded triangular cross-sections, but have little influence on the performance of surface plasmonic waveguides with rounded square cross-sections. Since the distribution of transverse magnetic field, effective index, propagation length and the mode area can be adjusted by the geometrical parameters, this kind of modified surface plasmonic waveguide can be applied to the field of photonic device integration and sensors.     

蝴蝶形中空表面等离子体波导的传输特性

本文设计了一种蝴蝶形中空表面等离子体波导,并对其传输特性进行了研究.采用频域有限差分法,对这种波导所支持的基模的能流密度分布、有效折射率、传播长度和模式面积随几何参数和工作波长的变化关系进行了分析.结果表明:沿纵向的能流主要分布在由四个圆洞所构成的上下两个尖角之间的区域,且越接近尖角,沿纵向的能流越大.对中空圆洞的半径、上下两排圆洞圆心间横向距离和左右两列圆洞圆心间的纵向距离进行调节,模式的有效折射率、传播长度和模式面积也随之变化.在工作波长确定的条件下,相对于b=r/4的情况来说,当b=r/2时,上下两个尖角之间的距离较大,场与金属的相互作用较弱,有效折射率就较大,传播长度也较大.在几何参数确定的条件下,相对于λ=705.0 nm的情形来说,在λ较大时,场的分布范围较大,场与金属表面的接触面积较大,场与金属的相互作用较弱,有效折射率较小,传播距离较长.与由两个和三个空心圆柱构成芯区的表面等离子体波导相比较,蝴蝶形中空表面等离子体波导具有良好的传输特性.如果在波导结构中心填充增益介质,可以克服较大的传播损耗,因此这种蝴蝶形中空表面等离子体波导可以用于光子器件集成领域和传感器领域.     

含偶次高阶项的厄米——高斯型短脉冲各参量的演化

从非线性薛定谔方程出发，用矩法和数值方法研究了含零阶、二阶、四阶厄米－高斯项的光脉冲在光纤中的传输，并进行了比较，结果表明，两者吻合较好，结果表明：在色散和晨线性效应存在的条件下，在光脉冲的传输中，厄米－高斯光脉冲的各阶项的能量在互相交换，四阶项的所占据的能量在逐渐减少，能量向两边辐射。     

Propagation properties of a modified surface plasmonic waveguide with an arc slot

We introduce a modified surface plasmonic waveguide with an arc slot. The dependences of distribution of energy flux density, effective index, propagation length and mode area of the symmetric mode supported by this waveguide on geometrical parameters and working wavelength are analysed by using the finite-difference frequency-domain (FDFD) method. Results show that the energy flux density distributes mainly in four corners which are formed by two arcs, and the closer to the corners it is, the stronger the energy flux density will be. The effective index, the propagation length and the mode area are influenced by geometrical parameters, including the width, the thickness and the arc radius of the surface plasmonic waveguide, as well as the working wavelength. It has been shown that the surface plasmonic waveguide with an arc slot has better propagation properties than the surface plasmonic waveguide with a straight slot. This work may be helpful for applying the slot surface plasmonic waveguide to integrated photonics.     

一种由椭圆形金属和介质纳米线组成的混合表面等离子体光波导的基模控制特性研究

本文研究了一种由三根并排放置的椭圆形金属-介质-金属纳米线构成的混合表面等离子体光波导所支持的电磁场基模的控制特性,中间是高折射率的介质纳米线,左右是两根对称放置的金属纳米线。研究结果表明,基模电磁场增强效应主要分布在三根纳米线形成的两个间隙区域,且对整个结构的几何参数有一定依赖性。因此,通过改变纳米线的几何尺寸、两根纳米线之间的间距以及介质的电磁参数,可以调整和控制这种波导所支持的基模的有效折射率、模式传输距离、归一化的模式面积和模式束缚因子等物理特性。基于这些有效的模式操控特性,这种混合型的表面等离子体光波导可以应用于高密度光子器件集成、纳米光子学和生物传感器等领域。     

Mode characteristics of nested eccentric waveguides constructed by two cylindrical nanowires coated with graphene

A kind of nested eccentric waveguide constructed with two cylindrical nanowires coated with graphene was designed. The mode characteristics of this waveguide were studied using the multipole method. It was found that the three lowest modes (mode 0, mode 1 and mode 2) can be combined by the zero-order mode or/and the first-order modes of two single nanowires. Mode 0 has a higher figure of merit and the best performance among these modes within the parameter range of interest. The mode characteristics can be adjusted by changing the parameters of the waveguide. For example, the propagation length will be increased when the operating wavelength, the minimum spacing between the inner and outer cylinders, the inner cylinder radius and the Fermi energy are increased. However, when the outer cylinder radius, the dielectric constants of region I, or the dielectric constants of region III are increased, the opposite effect can be seen. These results are consistent with the results obtained using the finite element method (FEM). The waveguide structure designed in this paper is easy to fabricate and can be applied to the field of micro/nano sensing.