锥脊波导SOA光耦合机制的理论分析

针对半导体光放大器（SOA）与单模光纤的耦合问题，详细介绍了当前最新的锥脊光波导耦合技术，用光波电磁场干涉理论建立了锥脊光波导的传输模式方程，并根据光波的全反射理论，揭示了锥脊光波导等效折射率的渐变规律，从理论上分析了锥脊波导SOA的光耦合机制，理论分析与相关报道的实验结果吻合。     

左手材料薄板波导中的传导模

推导了左手材料薄板波导中传导模的色散方程,分析了波导中存在传导模与波导材料和包敷材料参数取值范围之间的关系.数值算例证实了这些关系.     

有损矩形金属波导中TEmn模传播常数计算分析

运用边界阻抗法,论文推导出有损矩形金属波导中TEmn模传播常数计算公式。经验证,此公式与传统功率损耗法给出的结果一致,并且推导的传播常数公式可适用于全频率范围。研究结果对分析有损矩形金属波导的电磁传播有指导意义。     

铝合金异形波导管的热挤压

论述了Ｐ４Ａ１４８３－４型铝合金异形波导管的挤压模设计和挤压工艺选择；提出了采用分流组合模挤压工艺制造复杂形状的异形波导管。     

新型低损耗级联式1×4光分路器的优化设计

为改进传统Y分支光分路器损耗较大的缺陷,我们采用激模波导结构设计新型Y分支波导和由三个分支级联的新型Y分支波导构成低损耗1×4光分路器.设计中利用辐射模和本征基模的叠加来修正光波场,通过改善模匹配来降低分支耦合损耗,同时在1×4光分路器中加入直波导来改善和优化分路器的输出均匀性,并用有限差分光束传播法对该Y分支波导和1×4光分路器进行数值模拟.模拟结果表明,该结构具有均匀性好、损耗小和结构简单等优点,有利于器件的进一步集成和大批量生产.     

亚波长波导光栅导模共振研究

弱调制介质光栅可等效为平板波导,经其衍射的高级次子波与波导模式耦合时,形成导模 共振。由高级子波在介质光栅中的光程及菲涅耳相移,导出了垂直入射时弱调制介质光栅共振位置的解析表达式,其预测结果和严格耦合波理论所得值一致。导模共振对入射波参数和光栅参数极为敏感,具有窄带效应,可用来制作窄带滤波片。     

新型低损耗级联式1×4光分路器的优化设计

为改进传统Y分支光分路器损耗较大的缺陷,我们采用激模波导结构设计新型Y分支波导和由三个分支级联的新型Y分支波导构成低损耗1×4光分路器。设计中利用辐射模和本征基模的叠加来修正光波场,通过改善模匹配来降低分支耦合损耗,同时在1×4光分路器中加入直波导来改善和优化分路器的输出均匀性,并用有限差分光束传播法对该Y分支波导和1×4光分路器进行数值模拟。模拟结果表明,该结构具有均匀性好、损耗小和结构简单等优点,有利于器件的进一步集成和大批量生产。     

光波导显微技术测量微小厚度变化

在表面等离子波显微技术(SPM)的基础上,提出了一种新的反射型波导显微理论,并且进行了实验研究.这种显微技术采用棱镜波导耦合结构,在棱镜下底面依次镀有金属膜-波导层-样品层.利用导模共振吸收峰对样品层厚度敏感的特性,通过反射光强的测量来确定样品层厚度的变化值.和表面等离子波显微技术相比,光波导显微技术所采用的波导结构能够有效地削弱金属的吸收特性造成的影响,减小衰减全反射曲线的半峰全宽,进而提高波导显微对厚度变化的灵敏度.实验表明,光波导显微技术对厚度变化有很高的灵敏度.     

纳米多孔光波导漏模共振传感器的折射率灵敏度分析(英文)

在玻璃基片上射频溅射50 nm厚的金膜,然后利用TiO2胶体溶液在金膜表面制备了厚度约为320 nm的TiO2纳米多孔薄膜.以此双层膜为漏模光波导芯片,构建了基于Kretschmann结构的波长调制型光波导漏模共振(LMR)传感器.利用扫描电子显微镜(SEM)观测了TiO2纳米多孔薄膜的表面和横截面形貌.实验研究了在纳米多孔光波导中给定漏模的共振波长及折射率灵敏度与入射角的依赖关系.结果表明,随着入射角的增大,共振波长逐渐蓝移,折射率灵敏度随之下降.此外,与传统的表面等离子体共振(SPR)传感器进行了对比,结果表明在相同的共振波长下,纳米多孔光波导LMR传感器折射率灵敏度大于SPR传感器.     

磁光盘记录光场畸变分析

运用光波衍射理论，针对磁光盘建立了记录光场的数学模型。该数学模型可全面描述基片杂质大小、位置、透射率对记录光场的影响。利用该数学模型可进一步研究基片杂质与磁畴特性，以及盘片误码的关系。     

Schrödinger wave equation for confinement of photon in a waveguide

In the present work, electromagnetic field confinement in a subwavelength waveguide structure is obtained using concepts of quantum mechanics and uncertainty principle. Semi-macroscopic considerations of field interaction at the dielectric interfaces are used in this work. The modal field profile in the subwavelength waveguide is obtained by considering the photon as a particle in the waveguide having finite probability of tunneling. Thus, uncertainty of position is assigned to it. The momentum uncertainty is calculated from position uncertainty. Schrödinger wave equation for the photon is written by incorporating position-momentum uncertainty. The equation is solved and the field distribution in the waveguide is obtained. The field distribution and power confinement is compared with conventional waveguide theory. They were found in good agreement with each other.     

空气声源激发的浅海声场的理论研究

研究了将空气中声速分布建模为Epstein分布,水层和海底均为均匀分布的三层介质模型的条件下,空气中点源激发的水下声场。既推导得到了声压场的形式解,通过数值分析,表明空气中点源激发浅水波导,在水层中形成的波导简正波具有实数本征值,可以远距离传播,称其为"水波"。空气层中的Epstein波导简正波在水层中为非均匀波,传播速度取决于空气中声速,称其为"水面波",并指出空气中声源运动产生的水面波多普勒频移大于水波多普勒频移。     

Matrix method for two-dimensional waveguide mode solution

In this paper, we show that the transfer matrix theory of multilayer optics can be used to solve the modes of any two-dimensional (2D) waveguide for their effective indices and field distributions. A 2D waveguide, even composed of numerous layers, is essentially a multilayer stack and the transmission through the stack can be analysed using the transfer matrix theory. The result is a transfer matrix with four complex value elements, namely A, B, C and D. The effective index of a guided mode satisfies two conditions: (1) evanescent waves exist simultaneously in the first (cladding) layer and last (substrate) layer, and (2) the complex element D vanishes. For a given mode, the field distribution in the waveguide is the result of a ‘folded’ plane wave. In each layer, there is only propagation and absorption; at each boundary, only reflection and refraction occur, which can be calculated according to the Fresnel equations. As examples, we show that this method can be used to solve modes supported by the multilayer step-index dielectric waveguide, slot waveguide, gradient-index waveguide and various plasmonic waveguides. The results indicate the transfer matrix method is effective for 2D waveguide mode solution in general.     

金属表面等离子体激发的实时场分布研究

利用时域有限差分法的电磁场仿真软件建立了金属-绝缘体-金属波导结构模型,并通过持续扩展光源激发该波导结构产生表面等离子体波,研究了金属表面等离子体激发的实时场分布.结果表明,表面等离子体波的各电磁场分量可以沿着金属-绝缘体的接触面传播,但传播距离有限,且垂直于接触面向两侧指数衰减.     

A physical interpretation of elastic guided-wave reflection from normal ends of a waveguide

Studied in this paper are two-dimensional guided wave reflections from normal boundaries in an isotropic elastic media. By making use of the transverse resonance concept, the reflections of the waveguide modes from normal interfaces are interrogated. A general condition is obtained under which the guided waves in an isotropic medium will undergo no mode conversion when interaction occurs with a normal traction free or fixed end. Under some circumstances, similarities are obtained between waveguide modes and bulk-wave modes, for example, doubling of the displacement field at a free end and doubling of the stress field at a fixed end. The results obtained are applicable to all two-dimensional, guided-wave modes, along one waveguide direction with lossless boundaries on the surface(s) parallel to the waveguide direction, including all possible guided-wave modes, propagating and nonpropagating, in plates, one half space, interface of two different half spaces, layers on a half space, multilayer structures, and all axisymmetric modes in cylindrical structures. In addition, the function of displacement potentials is analyzed in the course of guided-wave mode conversion at a normal end.     

Photonic crystal waveguide-mode orthogonality conditions and computation of intrinsic waveguide losses

We simulate the propagation of light in a W1 planar photonic crystal waveguide with the three-dimensional finite-difference time-domain method and apply an inner product against previously calculated mode profiles to the simulated field cross sections. We show that this inner product satisfies mode orthogonality for both photonic crystal waveguides and segmented waveguides and use the obtained data to evaluate waveguide losses.     

一种基于波数积分方法的线源声场计算方法

提出了在Pekeris波导条件下,一种基于波数积分方法的线源声场中的稳定数值计算方法。通过对深度格林函数中上行波与下行波的归一化,得到稳定的系数矩阵,从而求得格林函数的解析解。对深度格林函数进行模式展开,验证了该方法得到的深度格林函数解析解的准确性。结合仿真实例,将该方法得到的波数积分模型与传统简正波模型KRAKENC的结果进行比较,结果显示,当某号简正波的波数与海底波数接近时,KRAKENC计算不出该号简正波,会导致KARKENC的计算结果不准确,而波数积分方法可以很好地解决该问题。因此,提出的方法可以作为Pekeris波导中线源激发声场的标准模型。     

Reproduction in free space of fields confined by 3-dimensional optical waveguides

Abstract

It is shown by using the Fresnel-Kirchhoff diffraction theory and the method of images that a scalar field confined by a 3-dimensional optical waveguide can be generated in free space by a suitable light source. In the method the boundaries of a waveguide are replaced by virtual sources. This allows one to present the wave guiding as the interference and diffraction of multiple light beams produced in free space by the guide equivalent source (Fresnel waveguide). Thus, the scalar optics of a 3-dimensional waveguide is presented as the free-space beam optics. The method is illustrated by construction of the Fresnel sources for the triangular, rectangular and hexagonal waveguides. The numerical examples demonstrate the diffraction-free and self-imaging propagation in the free-space of the eigenmodes of the Fresnel rectangular-waveguide.     

Ultrasensitive detection of 1,4-Bis(4-vinylpyridyl)phenylene in a small volume of low refractive index liquid by surface-enhanced Raman scattering-active light waveguide

This paper reports a novel surface-enhanced Raman scattering (SERS)-active light waveguide method for ultrasensitive detection of a sample dissolved in a small volume of low refractive index liquid. The SERS-active light waveguide demonstrated in this study was constructed via the light-guiding silica capillary. The surface of its inner wall was modified with SERS-active silver nanoparticles that can remarkably enhance Raman signals. The capillary with SERS-active modified layer was filled with the sample solution to form the SERS-active liquid core (LC) fiber. The incident laser beam travels through the waveguide in a totally reflective mode within the fiber wall and penetrates a small distance into the sample solution by the evanescent wave field. The Raman scattering of the analytes adsorbed onto the surface of the SERS-active modified layer can be excited by the laser beam and refracted into the fiber wall. Thus, a sample dissolved in low index liquid, e.g., methanol, can be quantitatively monitored by Raman spectroscopy and detection limit of its concentration is lower than 10(-9) mol/L.     

Planar waveguide refractive index distribution functions determined precisely from mode indices

The inverse WKB (IWKB) approximation has been extended to derive the index distribution functions from the measured mode indices of a planar waveguide. Through the use of this technique, the forms of the index distribution functions are obtained by IWKB approximation and a criterion is used to derive the functions accurately. The results are compared to the exponential and Fermi distributions. It is shown that the index profile, surface index, and waveguide depth can be obtained more accurately than with the original IWKB approximation. Finally, the index distribution function of a c-cut proton-exchanged LiTaO(3) waveguide is given by this technique, the mode indices calculated with this function agree with the experimental results in the range of 10(-4).