Factorization method for inverse obstacle scattering problem in three-dimensional planar acoustic waveguides

In this paper, we consider the inverse scattering problem of reconstructing a bounded obstacle in a three-dimensional planar waveguide from the scattered near-field data measured on a finite cylindrical surface containing the obstacle and corresponding to infinitely many incident point sources also placed on the measurement surface. The obstacle is allowed to be an impenetrable scatterer or a penetrable scatterer. We establish the validity of the factorization method with the nearfield data to characterize the obstacle in the planar waveguide by constructing an outgoing-to-incoming operator which is an integral operator defined on the measurement surface with the kernel given in terms of an infinite series.

A MATRIX METHOD FOR SOLVING PLANAR DIELECTRIC OPTICAL WAVEGUIDES

A matrix method used in multilayer stack of dielectric films is applied-to planar dielectric optical waveguides. A simple and applicable method for obtaining characteristic equation is presented.

Waveguide Bragg Grating for Fault Localization in PON

Femtosecond laser direct inscription is a technique especially useful for prototyping purposes due to its distinctive advantages such as high fabrication accuracy,true 3D processing flexibility,and no need for mold or photomask.In this paper,we demonstrate the design and fabrication of a planar lightwave circuit(PLC)power splitter encoded with waveguide Bragg gratings(WBG)using a femtosecond laser inscription technique for passive optical network(PON)fault localization application.Both the reflected wavelengths and intervals of WBGs can be conveniently tuned.In the experiment,we succeeded in directly inscribing WBGs in 1×4 PLC splitter chips with a wavelength interval of about 4 nm and an adjustable reflectivity of up to 70% in the C-band.The proposed method is suitable for the prototyping of a PLC splitter encoded with WBG for PON fault localization applications.

Optical Properties of the Coupling Interface for Planar Optical Waveguides

Planar optical waveguides are the key elements in a modern, high-speed optical network. An important problem facing the optical fiber communication system, specifically planar optical waveguides, is coupling. The current study presents a coupling model for planar optical waveguides and optical fibers. The various effects of the optical properties of the coupling interface were analyzed by the scalar finite difference beam propagation method, including the thickness, with or without the matching refractive index of the interface adhesive. The findings can serve as a guide for planar optical waveguide packaging.

A SIMPLE SOLUTION FOR MULTILAYER METALLIC OPTICAL WAVEGUIDES

A simple solution for a multilayer metallic optical waveguide by transforming it intoan equivalent three-layer slab waveguide is presented. The dispersion relation of the equivalentthree-layer slab waveguide is solved by using a simple iterative formula. This method itself isexact and can approach any accuracy desired. Moreover, the numerical results for four-layer andfive-layer structures show that the second-order solution is also accurate enough. It is simple andhas the same form of expressions for TE and TM modes and for different layer structures.

Preparation and Characterization of TiO2/Ormosil Planar Waveguide with Low Attenuation

TiO2/ ormosil planar waveguide was prepared by sol-gel method at low thermal treatment temperature （ 〈 200 ℃）. Scanning electron microscope, FT-IR spectrometer, spectrophotometer, atomic force microscopy, thermal analyzer, and dark m-line spectroscopy were used with the method of scattering-detection to investigate optical and structural properties. High optical quality waveguide film was obtained. The propagation loss of film was 0.569 dB/cm at a wavelength of 632.8 nm.

Effects of Group-Velocity Dispersion on the Self-Trapped Optical Pulses in a Planar Waveguide

We give the exact bright solitary wave solutions of(2+1)-dimensional nonlinear Schrödinger equation and analyze the effects of group-velocity dispersion(GVD)on the self-trapped pulses in a planar waveguide.The results show that the self-trapped pulses are unstable and collapse at higher peak power in a planar waveguide with the anomalous GVD,but the collapse does not occur in a planar waveguide with the normal GVD;the peak power required for self-trapping of the pulse in a planar waveguide with the normal GVD is less than the critical peak power for collapse of the pulses in a planar waveguide with the anomalous GVD.

Asymptotic Theory of Guided Modes for Cladded Slab Waveguides

Multilayer cladded slab waveguides have been solved by using asymptotic theory once or twice. Based on the solution of a three layer slab waveguide, the wave number of guided modes has been expanded in series of one or two small parameters. One side cladded slab, two side cladded slab and two parallel cladded slab waveguide system are demonstrated to show how to use this essentially analytic method. Numerical examples have also been given and compared with exact solutions, eved the first or second order solutions are highly accurate.

Theoretical research on terahertz wave generation from planar waveguide by optimized cascaded difference frequency generation

A novel scheme for high-efficiency terahertz(THz)wave generation based on optimized cascaded difference frequency generation(OCDFG)with planar waveguide is presented.The phase mismatches of each-order cascaded difference frequency generation(CDFG)are modulated by changing the thickness of the waveguide,resulting in a decrement of phase mismatches in cascaded Stokes processes and an increment of phase mismatches in cascaded anti-Stokes processes simultaneously.The modulated phase mismatches enhance the cascaded Stokes processes and suppress the cascaded anti-Stokes processes simultaneously,yielding energy conversion efficiencies over 25%from optical wave to THz wave at 100 K.

Characteristic Analysis of Diffraction from Restricted Output End Surface of Multiple Quantum Wells Planar Waveguide

Based on Rayleigh-Sommerfeld scalar diffraction formula, analyzed is the diffraction field distribution of the restricted output end surface of multiple quantum wells planar waveguide by slit. Obtained is its analytical expression of field distribution, which permits accurate and effective study on the characteristic of diffraction field from the restricted output end surface of the waveguide by slit. Then, the variation curve of the beam propagation factor M2 versus the slit width is computed by the second moment method. It is useful for understanding the restricted diffraction properties of the multiple quantum wells planar waveguide. When the slit half width is bigger than the core layer's half width, the beam propagation factor M2 value tends to a constant 1.108. Therefore, the corresponding field amplitude distribution is approximated by Gaussian function, and the far field divergence half angle(θ0,G=0.091 8) is calculated by matching efficiency method.

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。

一种终端间隙结构的波导缝隙阵列平板天线

为降低传统的波导缝隙阵列平板天线加工难度,提高环境适应性,分析了波导终端间隙结构对辐射波导输入阻抗的影响,提出了一种终端间隙结构的波导缝隙阵列平板天线,并给出了设计方法及22×4阵元Ka波段阵列的仿真结果。仿真结果表明:终端间隙尺寸较小时,终端间隙结构的波导缝隙阵列天线与传统的波导缝隙阵列天线性能基本一致;终端间隙结构的阵列在生产加工、环境适应性方面,具有较好的优势。

Design,Fabrication,and Testing of Single-Side Alignment of 16×0.8nm Arrayed-Waveguide Grating

A novel design of 100GHz-spaced 16channel arrayed-waveguide grating (AWG) based on silica-on-silicon chip is reported.AWG is achieved by adding a Y-branch to the AWG and arranging the input/output channel in a neat row,so the whole configuration can be aligned and packaged using only one fiber-array.This configuration can decrease the device’s size,enlarge the minimum radius of curvature,save time on polishing and alignment,and reduce the chip’s fabrication cost.

Temperature sensor based on polymer thin film optical waveguide

Based on attenuated total reflection （ATR） and thermo-optic effect, the polymeric thin film planar optical waveguide is used as the temperature sensor, and the factors influencing the sensitivity of the temperature sensor are comprehensively analyzed. Combined with theoretical analysis and experimental investigation, the sensitivity of the temperature sensor is related to the thicknesses of the upper cladding layer, the waveguide layer, the optical loss of the polymer material and the guided wave modes. The results show that the slope value about reflectivity and temperature, which stands for the sensitivity of the polymer thin film temperature sensor, is associated with the waveguide film thickness and the guided wave modes, and the slope value is the highest in the zero reflectance of a certain transverse electric （TE） mode. To improve the sensitivity of the temperature sensor, the sensor＇s working incident light exterior angle α should be chosen under a certain TE mode with the reflectivity to be zero. This temperature sensor is characterized by high sensitivity and simple structure and it is easily fabricated.

二氧化硅平面波导集成光开关器件研究

基于二氧化硅平面光波导平台,设计并制作了一种多模干涉马赫曾德型的低功耗热光开关。该器件结合了多模干涉耦合器的稳定性及二氧化硅波导和热光开关的低损耗等优势。经仿真,对器件参数进行了优化,并讨论了金属层与波导的间距对传输光强及功耗的影响。测试结果表明,该器件的结构稳定,偏振依赖小,插入损耗低于2 dB,能实现开关的转换,功耗为450 mW左右,开关响应时间为103µs和113µs,在1564 nm工作波长下消光比超过16 dB,尺寸为2.30 cm×0.25 mm。该器件不仅与互补金属氧化物半导体工艺相兼容,同时与光纤之间也有较好的兼容性。二氧化硅波导光开关器件具有成本低,产量大,性能稳定的优势,能给光通信及光计算的未来发展提供可靠的基础。

Automated visual position detection and adjustment for optical waveguide chips and optical fiber arrays

The alignment coupling between optical waveguide chips and optical fiber arrays is the basis of the alignment coupling of planar optical waveguide devices, and the precise position detection with angle and spacing adjustments is one of the key steps of alignment coupling. A methodology for position detection, and angle and spacing adjustment was proposed for optical waveguide chips and optical fiber arrays based on machine vision. The experimental results show angle detection precision levels higher than 0.05°, line detection precision levels higher than 0.1 μm, and detection time less than 2 s. Therefore, the system developed herein meets the precise requirements necessary for position detection, and angle and spacing adjustments for optical waveguide chips and optical fiber arrays.

Giant Goos–Hnchen shifts of waveguide coupled long-range surface plasmon resonance mode

A hybrid structure based on a planar waveguide （PWG） mode coupling a long-range surface plasmon resonance （LRSPR） mode is proposed to enhance the GH shift. Both the PWG mode and LRSPR mode can be in strong resonance, and these two modes can be coupled together due to the normal-mode splitting. The largest GH shift of PWG-coupled LRSPR structure is 4156 times that of the incident beam, which is 23 times and 3.6 times that of the surface plasmon resonance （SPR） structure and the LRSPR structure, respectively. As a GH shift sensor, the highest sensitivity of 4.68 x 107 λ is realized in the coupled structure. Compared with the sensitivity of the traditional SPR structure, the sensitivity of our structure is increased by more than 2 orders, which theoretically indicates that the proposed configuration can be applied to the field of high-sensitivity sensors in the future.

V波段低损耗波导密封与平面集成电路技术

V波段信号经过同轴电缆传输的损耗较大,所以主要通过波导进行传输V波段信号,但由于波导结构无法实现有源器件的集成,要集成有源器件需要转换为微带平面电路,而且V波段的有源器件均为裸芯片,要求波导转换为微带平面电路的结构必须实现气密,因此,为了实现平面集成,需要低损耗的气密的波导—微带过渡装置来完成,但目前V波段实现平面集成的结构均无法实现低损耗气密。本文提供了一种V波段低损耗波导密封与平面集成电路技术,在满足气密要求的同时,可实现波导到微带平面电路的过渡,且损耗较小。

天线在微波热疗中的应用研究综述

微波热疗天线是微波治疗癌症的关键因素之一.近年来,微波热疗天线技术得到了广泛的关注与研究,但本领域内相关综述鲜有报道.基于此,对现有的微波热疗天线技术进行整理,从介入式热疗、平面螺旋式、波导式、微带式、透镜式天线等主要方向对现有研究进行了归纳总结,阐述了各研究热点的模型特点和关键方法.最后,对微波热疗天线技术进行了总结梳理,并探讨了未来的研究热点方向.