Extraordinary transmission and reflection in PT-symmetric two-segment-connected triangular optical waveguide networks with perfect and broken integer waveguide length ratios

By adjusting the waveguide length ratio, we study the extraordinary characteristics of electromagnetic waves propagating in one-dimensional(1D) parity-time-symmetric(PT-symmetric) two-segment-connected triangular optical waveguide networks with perfect and broken integer waveguide length ratios respectively. It is found that the number and the corresponding frequencies of the extremum spontaneous PT-symmetric breaking points are dependent on the waveguide length ratio. Near the extremum breaking points, ultrastrong extraordinary transmissions are created and the maximal can arrive at, respectively, 2.4079 × 1014 and 4.3555 × 1013 in both kinds of networks. However, bidirectional invisibility can only be produced by the networks with broken integer waveguide length ratio, whose mechanism is explained in detail from the perspective of photonic band structure. The findings of this work can be useful optical characteristic control in the fabrication of PT-symmetric optical waveguide networks, which possesses great potential in designing optical amplifiers,optical energy saver devices, and special optical filters.     

Asymmetric nonlinear-mode-conversion in an optical waveguide withPT symmetry

Asymmetric mode transformation in waveguide is of great significance for on-chip integrated devices with one-way effect, while it is challenging to achieve asymmetric nonlinear-mode-conversion (NMC) due to the limitations imposed by phase-matching. In this work, we theoretically proposed a new scheme for realizing asymmetric NMC by combining frequency-doubling process and periodic PT symmetric modulation in an optical waveguide. By engineering the one-way momentum from PT symmetric modulation, we have demonstrated the unidirectional conversion from pump to second harmonic with desired guided modes. Our findings offer new opportunities for manipulating nonlinear optical fields with PT symmetry, which could further boost more exploration on on-chip nonlinear devices assisted by non-Hermitian optics.     

Optical transmission loss in tin oxide thin film waveguide

This paper reports the optical transmission loss of tin oxide thin film waveguide. The effect of oxidation temperature, thickness and air ageing (40 days at room temperature) was studied. The vapour chopping technique has been used successfully to reduce the optical transmission loss. The vapour chopped tin oxide thin film waveguide (2.90-3.60 dB/cm) showed smaller transmission loss than those of nonchopped tin oxide thin film waveguide (4.16-4.74 dB/cm). Transmission loss was found to be a function of oxidation temperature and thickness. Due to increased oxidation temperature, transmission loss was found to decrease. The effect of increase in thickness was to increase the transmission loss. The air ageing effect caused the increase in transmission loss whereas the effect was found lesser in the vapour chopped tin oxide thin film waveguide.     

基于倏逝场耦合的石墨烯波导光传输相位特性仿真与实验研究

石墨烯材料应用到各种光波导器件中正成为新一代光子器件的重要发展方向之一,目前基于石墨烯的光纤和集成光子器件研究越来越受到国内外的重视. 本文建立了一种由微纳光纤耦合光倏逝场,并在石墨烯薄膜中传输的模型. 通过有限元分析法,研究了光在这种石墨烯波导中传输光场的强度分布和相位特性,并通过实验进行了验证. 结果表明,沿着微纳光纤-石墨烯光波导传播的倏逝场的强度分布和相位均受石墨烯材料作用,石墨烯材料能有效聚集和导行波导中传输的高阶模,在单位传输长度上具有更密集的等相位面. 本文提出了一种利用微纳光纤耦合光倏逝场研究石墨烯相位响应特性的新方法,对基于石墨烯波导的新型调制器、滤波器、激光器和传感器等光子器件的设计和应用具有一定的参考意义. 关键词： 石墨烯平面光波导 倏逝波 光场强度 相位     

Wavelength conversion in optical transport networks

The introduction of optical technology in the path layer of a transport network is analyzed; in particular, the impact of all-optical wavelength conversion is examined. Two basic optical cross-connect schemes based on space switching and on wave-length switching, respectively, and two types of wavelength converters are considered. The wavelength converters are, respectively, based on four-wave miring (FWM) in semiconductor optical amplifiers (SOAs) and on cross-phase modulation (XPM) obtained by two SOAs put in an interferometric configuration. An analysis of transmission performances of optical transport networks employing both types of wavelength conversion and both the node architectures is reported. The performances are evaluated by means of a system modeling that facilitates considering physical phenomena occurring during transmission and all the important transmission impairments. The analysis reveals that both the types of converters can be employed with different features and limitations, according to the considered network and switching architecture.     

Extension of the radiation spectrum method for the reflection calculation at the end of a strongly guiding optical waveguide

In this work we extend the radiation spectrum method (RSM) with evanescent modes to use it for the calculation of the reflection coefficient at the end of a strongly guiding dielectric waveguide. The extension is made by considering the coupling between the radiation (or evanescent) modes at both sides of the optical discontinuity. To insure the convergence of the method, this extension is achieved analytically. Using this technique, we show that for small guide width, the generation of evanescent modes results in a complex reflection coefficient. The magnitude and the phase of the reflection coefficient are calculated and compared with the simple theory of the effective index as well as the finite difference time domain (FDTD) technique. The spectra of the transmitted and reflected fields are also obtained.     

感应耦合等离子体刻蚀在聚合物光波导制作中的应用

提出了利用感应耦合等离子体(ICP)刻蚀技术提高聚合物光波导器件性能的方法,介绍了ICP刻蚀技术的原理和优点。选取聚甲基丙烯酸甲酯-甲基丙烯酸环氧丙酯(P(MMA-GMA))作为波导材料,采用氧气作为刻蚀气体,研究了ICP参数变化对刻蚀效果的影响。介绍了倒脊形光波导的制备过程,采用改变单一工艺参数的方法,分析了刻蚀效果随时间、功率、压强、气体流量等参数的变化,对参数优化后刻蚀得到的凹槽和平板结构进行了表征。实验结果表明:在天线射频功率为300 W,偏置射频功率为30 W,气体压强为0.5 Pa,氧气流速为50 cm³/min的条件下,可获得侧壁陡直、底面平整的P(MMA-GMA)凹槽结构。     

支撑光网络发展的硅基光电子技术研究

作为大规模集成电路和化合物半导体光电子器件的制造技术共同构成的一门高新技术 ,硅基光电子技术越来越受到重视 .文章着重介绍中国科学院半导体研究所外延生长SiGe/Si量子结构和Si基器件研究的结果 :采用自行设计的UHV/CVD系统 ,成功地生长出Ⅱ型SiGe/Si量子阱和量子点 ,直到 2 5 0K仍能观察到自组织生长Ge/Si(0 0 1 )量子点的发光峰 ;研制成功SiGe/Si谐振腔增强型光电二极管 (RCEPD)、Y分支MZI光调制器和多模干涉 -马赫 -曾德干涉型光开关等Si基光电子器件 ;1 .3μm处RCEPD的量子效率达到 4 .2 % ,- 5V偏压下暗电流密度 1 2 pA/ μm2 ;2× 2热光型光开关的响应时间小于 2 0 μs,两输出端关态串扰为 - 2 2dB ,通态串扰为 - 1 2dB .     

纳米集成光路中的光源、光波导和光增强

使用近场光学显微术(scanning near-field optical microscopy, SNOM)研究了ZnO亚微米线端面出射性质,不同空间形貌Ⅱ-Ⅵ族半导体荧光器件光波导特性,二维光子晶体、准晶光子晶体对LED的出射增强作用以及表面等离激元(surface plasmon polariton, SPP)与半导体纳米荧光器件的相互作用,对纳米集成光路中的光源、光波导、光增强三个重要问题做了实验和理论上的分析.研究发现半导体微纳米线端面出射光束的质量与样品的直径有密切关系.通过合理地设计其直径和 关键词： 纳米集成光路 扫描近场光学显微术 光波导 光增强     

纳米集成光路中的光源、光波导和光增强

使用近场光学显微术(scanning near-field optical microscopy, SNOM)研究了ZnO亚微米线端面出射性质，不同空间形貌Ⅱ-Ⅵ族半导体荧光器件光波导特性，二维光子晶体、准晶光子晶体对LED的出射增强作用以及表面等离激元(surface plasmon polariton, SPP)与半导体纳米荧光器件的相互作用，对纳米集成光路中的光源、光波导、光增强三个重要问题做了实验和理论上的分析.研究发现半导体微纳米线端面出射光束的质量与样品的直径有密切关系.通过合理地设计其直径和     

System degradation due to phase error induced crosstalk in WDM optical networks employing arrayed waveguide grating multi/demultiplexer

The phase error induced crosstalk within arrayed waveguide gratings (AWG) have been investigated theoretically as well as simulation. For WDM system, a crosstalk level of −21.9 dB causes a power penalty of 1 dB for 64 channels and less than 0.5 dB for 16 channels and 32 channels, respectively. For crosstalk level of −30 dB and below, the power penalty is negligible. Crosstalk due to phase error also causes higher power penalty at higher bit rate. Bit rate of 10, 20 and 40 Gbits/s causes power penalty of 1 dB with crosstalk level of −41.5, −46.25 and −49 dB, respectively.     

Enhancement of sensitivity in optical waveguide sensors using left-handed materials

We show analytically that the sensitivity of an optical waveguide sensor can be dramatically enhanced by using a metamaterial with negative permittivity and permeability. The variation of the sensitivity of the proposed waveguide sensor with different parameters of the waveguide is studied. It is found that the sensitivity of the sensor increases with the increasing thickness of the metamaterial due to the surface polariton generation.     

Theoretical study of polymeric metal clad optical waveguide polarizer

Planar optical waveguides consisting of thin dielectric films and buffer layers with metal cladding have been investigated theoretically. A computer program was written to calculate the exact zeroes of complex eigenvalue equation for TE and TM modes in multilayer metal clad waveguide polarizer. Numerical results and illustrations are given for Polycarbonate waveguide with other polymers as buffer and Al, Ag and Au as cladding metals at . It is also shown that, using thin (finite) films of metal produce more efficient polarizers as compared to semi-infinite metal films. Effect of low index buffer layer on attenuation of TM/TE modes is also investigated.     

离子交换LiNbO_3:Fe平面光波导中两波混合的研究

本文利用耦合波理论分析推导了单模平面光波导中两波混合的耦合波方程和弱相干光放大率的表示式.并且,在LiNbO_3:Fe单模平面光波导中进行了两波混合的实验研究,得到了与理论分析相符合的结果.     

Investigation of waveguide and process parameter of nonlinear optical waveguide in CdS_xSe_(1-x)doped glass

For the first time,it is experiementally verified that the index profile of K~ —Na~ ion-exchanged waveguide in CdS_xSe_(1-x)doped glass follows a second-order polynomial dis-tribution.Mode-dispersion curves have been obtained by computing simplified mode equationin WKB approximation and verified by experiment.Diffusion constant has been measured ac-curately.Technical basis is provided for the design and fabrication of all-optical switching de-vices in this kind of nonlinear waveguide.     

光子晶体波导中的孤子传输及其延迟特性研究

研究了正方晶格和三角晶格空气背景硅介质柱光子晶体线缺陷波导导模左带隙边缘处的亮孤子脉冲传播特性及其慢光延迟特性. 采用平面波展开法仿真分析了波导相邻两行介质柱大小r₁和r₂以及波导宽度D对孤子脉冲传输所需峰值功率P₀和延迟时间T_s的影响,总结了其变化规律. 通过调整波导结构得到了正方晶格和三角晶格优化波导结构,优化后,正方晶格结构波导P₀减小了81.17%,T_s增加了66.32%;三角晶格结构波导P₀减小了73.7%,T_s增加了67.63%,实现了孤子传输性能的大幅度优化. 关键词： 光子晶体波导 光孤子 峰值功率 延迟时间     

Overview of hybrid optical neural networks

This paper reviews optical architectures for the implementation of hybrid neural networks. Optics is mainly applied to implementing the matrix-vector or tensor-matrix multiplication. In addition, the general background of neural networks as well as a brief discussion on holographic associative memory are also given.     

Numerical calculation of the spectral bandwidth of optical parametric amplification in hybrid organic/inorganic planar waveguide

The spectral bandwidth of three-wave-mixing optical parametric amplification has been investigated in a simple hybrid polymer/ion exchanged planar optical waveguiding structure. A nonlinear polymer is deposited on the top of a glass substrate with a waveguide realized by the ion-exchange technique. The spectral bandwidth is determined by expanding the wave-vector mismatch in a Taylor series and retaining terms through second order. The relation between parametric bandwidth and gain bandwidth is clearly defined.     

Design of short length and C+L-band mismatched optical coupler with waveguide weighted by the Blackman function

A mismatched optical coupler with waveguide weighted by the Blackman function is numerically investigated in the demand of short length, C+L-band, and low crosstalk. Utilizing the full factorial design, the structure parameters of coupling waveguide are obtained by beam propagation method. In the condition of crosstalk of −35 dB, the mismatched optical coupler with proper selected waveguide structure parameters is found to have a coupling length of 3.60 mm in the transmission wavelength ranges of C+L-band (1.53-1.61 μm). Obviously, the selection and design of waveguide structure are very important to satisfy the qualities of a mismatched optical coupler for the demand of short length, broad bandwidth, and low crosstalk.     

4通道交叉型二氧化硅光波导延迟线阵列的设计与制备

设计并制备了一种高集成度、低成本、低损耗4通道交叉型二氧化硅光波导延迟线阵列。利用BPM软件对交叉结构光波导延迟线的Y分支的损耗、弯曲损耗进行数值模拟。综合考虑器件尺寸和损耗参数,设计交叉型延迟线结构的弯曲半径最小为1 500 μm,引入优化的锥口Y分支结构和垂直相交波导结构。采用标准半导体制作工艺制备器件,测试得到了器件的红外输出光斑,延迟线延迟时间分别为0、113、226和339 ps。4通道二氧化硅延迟线阵列能实现相邻通道相等的延迟时间间隔,且可通过集成实现延迟时间的增加,同时输出端可以与光纤阵列集成。