太赫兹传输波导器件研究进展

随着太赫兹技术的发展,太赫兹传输波导器件的研究成为待解决的重要问题之一。太赫兹波位于微波与红外光之间,寻找高效的传输、耦合器件一直是研究人员的目标。主要介绍了太赫兹传输波导研究现状,并总结了各类型太赫兹波导的优势与不足。根据材料与结构分别对金属波导、介质波导的研究进展进行了分析。其中金属波导包括裸金属线波导、微结构波导、空芯波导以及平板波导,介质波导包括介质空芯波导、多孔芯波导以及微结构波导。最后分别对太赫兹传输波导未来需要解决的研究方向进行了展望。     

Leaky Waveguide: TE/sup cir//sub 01/ Circular Waveguide Periodic Array of Circular Apertures

This paper describes propagation characteristics of periodic leaky waveguides for helix waveguides and solid metal waveguides carrying a TE/sup cir//sub 01/ mode based primarily on experimental studies. For low-loss leaky waveguides, this type has not been considered feasible, because of the critical problem encountered in mode conversion-reconversion at the circular apertures. Additional loss due to the periodic array of the circular apertures and TE/sup cir//sub 01/ loss/frequency characteristics of the periodic leaky waveguide using helix waveguides and solid metal waveguides are measured by the shuffle-pulse method in the X-band. The periodic leaky waveguides using solid metal waveguides are seen to be acceptable for practical use as a low-loss leaky waveguide system, according to these measurements.     

Fabrication and performance analysis of polymer light waveguides in EOPCB

A new method, named as doctor-blaring, is presented to fabricate light waveguides in electro-optical printed circuit board （EOPCB）. This new technology is proven to be suitable for the fabrication of the large size waveguides. The performance parameters of the light waveguides fabricated by the proposed method as well as the influence of the parameters on the performance of the waveguides are analyzed and simulated. The results demonstrate the feasibility of the method to fabricate the polymer waveguides.     

弯曲光波导端面修饰的设计方法

光波导的弯曲损耗一直是集成光学中一个值得人们重视的问题,为有效地减小光波导弯曲损耗,弯曲光波导的设计成为集成光学波导设计中的一个重要内容.本文在弯曲光波导保形变换方法的基础上,应用几何光学分析方法给出了波导弯曲损耗产生的简洁的物理图像,从而深入地分析了弯曲损耗产生的根本原因,并由此提出了弯曲光波导端面修饰的设计方法.理论分析表明,与传统的弯曲的光波导设计相比,该种设计方法可以有效地减小导波的模式泄漏,从而减小波导弯曲损耗.尤其是在弯曲光波导曲率半径、材料折射率等参数被设定的情况下,该种设计方法成为一种有效的设计方法.     

Characterization and Modeling of Laser Micromachined Periodically Corrugated Metallic Terahertz Wire Waveguides

Finite element method simulations of periodically corrugated metal terahertz wire waveguides have been conducted with concurrent analysis done on both the near-field confinement properties and the far-field emission properties at the end of the waveguides. This modeling was used to guide the choice of design parameters for the fabrication of waveguides with laser micromachining. The waveguides were characterized with a fiber-coupled terahertz time-domain spectroscopy and imaging system. The propagation properties as well as the frequency dependent diffraction at the end of the wire waveguides were examined and compared to straight, non-engineered metallic wire waveguides.     

金属包层渐变折射率平板波导传播特性

本文采用多层线型分割近似，结合欧姆损耗微扰法，分析了金属包层渐变折射率平板波导的传播特性。按此方法计算了几类典型波导的传播常数数值，结果均与精确值相吻合，且物理概念清楚，计算方法简单。     

Vectorial wave analysis of dielectric waveguides for optical-integrated circuits using equivalent network approach

A vectorial wave analysis of the propagation characteristics of open dielectric waveguides for optical-integrated circuits using an equivalent network approach is presented. In this approach, all of the contributions from the discrete and continuous parts of the spectrum and from the TE-TM coupling, which are neglected in the earlier equivalent network approach, are taken into account. To show the validity and usefulness of this formulation, examples are computed for optical strip waveguides, rib waveguides, rectangular dielectric waveguides, embossed waveguides, and embedded waveguides.     

求解非均匀平面波导导模的一种新方法

本文给出一种新方法,用多层平板波导逼近非均匀平面波导,借助递推公式用牛顿切线法求解本征值方程,以求出非均匀平面波导导模的传播常数与模场分布。本方法优点在于程序简短通用,计算工作量小,求得结果与精确数值解十分吻合(直至近截止区)。本文给出了各种类型的非对称与对称渐变折射率平面波导的结果。     

Phase space evaluation of distributed-index branching waveguides

In this paper, we propose a new evaluation concept for characterizing multimode optical branching waveguides. In a ray tracing to simulate multimode branching waveguides, we introduce a phase space expression with the ray position and slope in order to describe the modal distribution of guided light. We have applied this technique for branching waveguides, which have a parabolic distributed-index, and clarified branching characteristics. Experimental results obtained for diffused branching waveguides are compared with theory.     

Propagation of TE Modes in Nonuniform Waveguides

The conditions for TE mode propagation in rectangular waveguides with nonuniform dielectric media are established. An equation is derived for determining the capacitivity functions which have equivalent curved waveguides with uniform dielectric media. The types of variable dielectric waveguides which have equivalent curved wall waveguides and a separable wave equation are determined.     

Modal analysis of multi-connected waveguides

A general analysis for the modal characterization of multiconnected uniform, hollow, conducting waveguides is presented. It is relevant to waveguides with an `outer' conductor for which analytical Green's functions are known and `inner' conductors described by integral equations. The transverse electromagnetic (TEM)-mode space is analyzed, and singularities of the integral equations are studied to determine the higher-order modes. The cases of parallel wires into rectangular waveguides and above a ground plane are addressed in detail; experimental results about a complex multiwire line are reported. Mixed coaxial and circular offset coaxial waveguides are also analyzed. Spurious solutions arise due to the structure of the integral equations for multiconnected waveguides. Criteria to discard such modes are presented     

Attenuation in wall-impedance waveguides: a new approach

The Rayleigh-Schroedinger power expansion of perturbed eigenvalues is used to determine propagation constants in wall-impedance waveguides, the final objective being a design procedure for trunk-communication waveguides. Examples of applications, where corrections up to the fifth order are accounted for, include ideal helix waveguides and thickly dielectric-lined circular waveguides.     

Enhancement of power transfer in periodic array of optical waveguides via intermediate Bloch states

A directional coupling mechanism between different waveguides in a periodic array of waveguides is suggested. The optical power transfer between two different waveguides is mediated by the coupling between zero-order modes of two of the waveguides and the second band of the periodic structure. Analytical solutions for the no-detuning (narrow band) and far-from-resonance cases are presented. The far-from-resonance case is shown to resemble a simple two-mode system with complete optical power transfer between the two waveguides, coupled by localized gratings. The transfer is mediated by the second band of the periodic structure. The transition length depends strongly on the shape of the perturbation, and depends exponentially on the distance between the waveguides, yet it allows us to transfer power from one waveguide to another at such distances, for which the transition via conventional directional tunneling mechanism is impossible. Our analytical results are supported by numerical calculations carried out for a model problem with realistic parameters.     

Scattering loss of antiresonant reflecting optical waveguides

The scattering loss of two-dimensional antiresonant reflecting optical waveguides (ARROW) and of ARROW-B, which has a similar structure to ARROW and less polarization dependence, are analyzed by the first-order perturbation theory. Calculated results are compared with those of conventional three layer waveguides. Optimum design for the reduction of scattering loss of these ARROW-type waveguides is discussed. It was found that the scattering loss of ARROW-type waveguides is no larger than that of a conventional waveguide having a relative refractive-index difference, Δ of 2.5%, despite each interface of ARROW-type waveguides having a large Δ, normally larger than 20%. The optimum design for the reduction of essential radiation loss of ARROW is also optimum for the reduction of scattering loss     

弯曲光波导模拟优化研究

用时域有限元差分（FDTD）方法弯曲光波导的优化仿真，减小弯曲光波导损耗。采用OPTIFDTD软件在曲率半径增大到一定的情况下，弯曲损耗在各种损耗中不占优势。在半径一定的条件下，适当选择波导的各个参数进行优化，可以使弯曲损耗达到最低，模拟了弯曲光波导中光的传播，得到了弯曲损耗的变化规律，波导参数不同，弯曲损耗不同，其中有一最佳参数点，由此得到弯曲光波导的参数优化设计值。     

Ring resonators composed of GeO2-doped silica waveguides

Ring resonators composed of GeO₂-doped silica waveguides fabricated on silicon substrates by a flame hydrolysis deposition method are described. GeO₂-doped silica waveguides are developed to provide a lower propagation loss than that of TiO₂ -doped silica waveguides. Since the finesse and transmission at resonance is determined mainly by total loss in the ring, the loss characteristics of the fundamental components are investigated in detail. Experimental and theoretical investigations show that a finesse of the ring resonator for GeO₂-doped silica waveguides is about 2.7 times higher than that for TiO₂-doped silica waveguides with the same transmission at resonance     

An Extension of the Effective Index Method to Analyze Leakage Losses in Rib Type Waveguides

An extension of the effective index method is proposed as a tool to investigate leakage losses in two-dimensional waveguides. The above method, referred to as the Extended Effective Index Method (EEIM), utilizes the Transfer Matrix Technique (TMT) for the calculation of the complex propagation constants. The results show that the EEIM can be applied to conventional rib leaky waveguides as well as to rib ARROW leaky waveguides. The results for rib ARROW waveguides show excellent agreement when compared to those obtained with Finite Element Method.     

激光直写法制备条形光波导中的功率密度阈值

采用溶胶-凝胶法(sol-gel)在Si基SiO2衬底上制备了SiO2-TiO2芯层薄膜,构成了以SiO2为下包层,空气为上包层的平面光波导。利用光纤激光器对平面波导的芯层进行直写,结合后续的化学腐蚀工艺得到了SiO2-TiO2条形光波导,并着重研究了激光直写波导过程中存在的功率密度阈值以及阈值随薄膜预热处理温度的变化关系。研究结果表明,激光直写SiO2-TiO2波导存在起始收缩阈值和烧蚀损伤阈值;随着薄膜热处理温度的提高,两个阈值同时增大,其中损伤阈值的增大趋势要大于收缩阈值;因而薄膜可承受的直写光斑直径变小,所得波导宽度显著减小。最后对直写制得条形光波导的导光性能作了测试分析,验证了波导的三维导光性。     

非对称单脊波导几何尺度对截止特性的影响

截止波长和带宽是脊波导中的两个重要参数,采用实验方法测试脊波导的性能很难进行精确控制,而且实验设备非常昂贵。有限元法是目前电磁场数值分析中的主流方法之一,文中用有限元法对脊波导进行数值模拟分析,给出了非对称单脊波导各种几何尺度下的截止波长及主模带宽的数值计算结果,对脊波导的设计与制作具有一定的参考价值。     

Dispersion and radiation loss characteristics of antiresonantreflecting optical waveguides-numerical results and analyticalexpressions

Propagation characteristics of novel single-mode slab waveguides, ARROW (antiresonant reflecting optical waveguides), ARROW-B, and their modified configurations, are investigated. The dispersion and radiation loss characteristics, field profile, confinement factor, and spot size of these ARROW-type waveguides are analyzed in detail by a mode analysis method using the system interference matrix. Approximate expressions for these characteristics are obtained in simple forms, which provide useful suggestions for the design of these waveguides. Possible combinations of materials and design conditions of ARROW-type waveguides are discussed on the basis of these results