A novel proposal for all optical 3 to 8 decoder based on nonlinear ring resonators

In this paper, a 3 to 8 optical decoder was proposed using nonlinear photonic crystal ring resonators. For realizing the 3 to 8 decoder, we combined seven 1 to 2 optical decoders. In the proposed structure, X, Y and Z serve as input ports. By combination of these ports, one can control which output port to be ON. The maximum time delay of the proposed structure is about 6?ps.     

Single photon transport in one-dimensional coupled-resonator waveguide coupling to a whispering gallery resonator interacting with a semiconductor quantum dot

We theoretically investigate the hybrid mechanism for transmission of a single photon in one-dimensional coupled microcavity waveguide coupled to a whispering-gallery resonator interacting with a semiconductor quantum dot (QD). The QD is modeled as a V-type three-level system. The reflection and transmission coefficients for a single photon propagating in the hybrid system are deduced by using the discrete coordinates approach. The resonator–QD coupling strength, intermode backscattering, and the detuning between the resonator and the QD, respectively, which affect the transport properties of the single photon, are analyzed. We also compare the single photon transport properties in the waveguides with sinusoidal, linear, and quadratic form dispersion relations.     

Excess noise in strip off-axis confocal unstable resonators

The lowest-loss mode and higher-order modes in strip off-axis confocal unstable resonators are calculated by the eigenvector method. The moduli of all pairs of the adjacent order eigenvalues exhibit crossing behavior. For the lowest- and next-lowest-loss modes, crossings occur when the equivalent Fresnel number N _eq is close to s?+?0.08 (s positive integer), and the lowest-loss mode profile calculated by the Fox–Li iteration is no longer self-reproducing, but the superposition of both eigenmodes with unfixed complex weights varies as the number of iterations. Numerical calculations of excess noise factors K in strip off-axis confocal unstable resonators are described in detail. The value of K shows an irregular resonance switching against N _eq. The hybrid model presented by van Eijkelenborg et al. is modified in this paper, and shows a good quantitative agreement with nonorthogonality theory.     

All-optical photonic crystal AND,XOR, and OR logic gates using nonlinear Kerr effect and ring resonators

In this article, two structures are proposed for all-optical AND, XOR, and OR logic gates based on nonlinear photonic crystals. The proposed structures include a Y-junction and ring resonator-based limiters. Two different structures are designed as the limiter in order to produce AND–XOR and AND–OR logic gates. Nonlinear rods of proposed structure have been used in order to create the frequency shift for different values of input power. Finite difference time domain method has been utilized to simulate the performance of proposed logic gates. Simulation results show that the smallest ON–OFF logic-level contrast ratio for the structures proposed for AND–XOR and AND–OR logic gates are 20.29 dB and 16.7 dB, respectively.     

计及压电效应时矩形振子的三维振动研究

在计及压电效应的情况下，本文利用解析方法对有限尺寸压电陶瓷矩形振子的三维振动进行了研究，推出了振子耦合振动的频率方程，并对振子的振动模式进行了分析。理论研究表明，利用本文中的解析法研究振子的耦合振动，计算简单、物理意义明显。与传统的一维理论分析方法及数值方法相比，由于本研究考虑了振子的压电效应以及不同振动模式不同的相互耦合，因此，振子的理论计算频率与测量值更加符合。     

A novel pressure sensor based on series-coupled double microring resonators with a simple beam

We propose and analyse a novel optical pressure sensor based on series-coupled double microring resonators (SDMRRs) on a simple beam. The pressure applied on the sensor is measured through the change of the optical transmission spectrum at the output port. The optical transmission performances of the SDMRRs have been analysed and compared with the single and paralleled-coupled structures by the method of finite element analysis and numerical simulation. The simulation results showed that the stress sensitivity is 0.0225?kPa^–1 and linear measurement range of the sensor is 30?kPa. Furthermore, the influence of the amplitude transmission coefficient, half round phase shift and microring radius on the sensitivity have been investigated to optimize the sensor performance. This proposed sensor can be used for the smaller pressure detection in automotive, aerospace, oil/logging equipment and other harsh environmental application.     

AlN films sputtered on iridium electrodes for bulk acoustic wave resonators

We report on the growth of highly c-axis-textured aluminum nitride (AlN) films sputtered on iridium layers for thin film bulk acoustic microresonator applications. Iridium films were evaporated on oxidized silicon covered with Ti or Mo/Ti seed layers to improve crystal quality and adhesion. The crystal quality of the AlN films as a function of the crystal structure of the iridium electrode and its pre-conditioning by Ar⁺ bombardment was analyzed by X-ray diffraction, atomic force microscopy and wet chemical etching. Solidly mounted resonators using a single low-impedance layer of silicon dioxide for acoustic isolation were fabricated for a preliminary assessment of the piezoelectric activity of AlN films and the influence of the AlN/Ir stack on the performance of the devices. The electromechanical coupling factor of the AlN films was derived by fitting the electrical response of the resonators to Mason's physical model. AlN films exhibited very high coupling factors (7.5%) barely dependent on the width of the rocking-curve around the AlN 00·2 reflection. The high acoustic impedance of iridium electrodes provided resonators with quality factors higher than those of similar resonators built on lighter electrodes, such as molybdenum.     

Multi-objective design optimization of electrostatically actuated microbeam resonators with and without parameter uncertainty

Electrostatically actuated microbeam resonators are widely used components in microelectromechanical systems for sensing and signal filtering purposes. Due to the uncertainties resulting from manufacturing processes, material properties, and modeling assumptions, microbeam resonators may exhibit significant variations in their performance compared to nominal designs. There has been limited research on the performance prediction and the design optimization of such microsystems while accounting for relevant uncertainties. In this study, such uncertainties are considered in terms of the variability of parameters that define the dimensions, the material properties, and the operating conditions of the device. In addition, uncertainties with respect to a two-dimensional model of a microbeam resonator subject to electrostatic actuation are considered. A finite element model consisting of both the microbeam and the substrate is developed. The actuation forces are predicted by a reduced order electrostatic model, which accounts for the electromechanical interaction. A computationally efficient procedure is presented for simulating the steady-state dynamic response under electrostatic forces. The probabilistic performance of the microresonator is investigated using Monte Carlo simulation. A genetic algorithm is used to optimize the stochastic behavior of the microbeam resonator. The design is posed as combinatorial multi-objective optimization problem. Two design criteria describing the filter performance in terms of the shape of the frequency–response curve are simultaneously considered. The numerical results demonstrate the effectiveness of this procedure for the multi-objective optimization design of microbeam resonators and the importance of considering parameter uncertainty in the design of these devices.     

Routes to various breather solitons in whispering-gallery-mode resonators through the variational method

In this paper, the dynamics of the optical field in the whispering-gallery-mode resonator described by the Lugiato–Lefever equation is studied by means of the variational method. For some special cases, exact explicit family of analytical breather-type solitons, such as time-periodic breather and space-time periodic breather are obtained. It is found that the pumping parameter, the detuning parameter and the dispersion coefficient, influences the nature of the optical field in the whispering-gallery-mode resonators.     

单层网壳结构风振响应的主要贡献模态识别

网壳结构具有频谱分布密集、振型复杂的动力特性，在对该类结构进行风振响应分析时，通常存在着一些对响应贡献较大的高阶振型，但由于其频率较高而容易被忽略。因此，研究网壳结构风振响应的主要贡献模态分布规律有利于提高结构风振响应计算的精度和效率。本文利用Ritz-POD法，分析了单层球面网壳和单层柱面网壳结构风振响应的主要贡献模态，着重考察了主要贡献模态的自身参振能力。及其与脉动风压空间分布模式之间的关系。在此基础上，初步给出了网壳结构风振响应的主要贡献模态识别准则。     

Amorphous WO3-x thin films with color characteristics tuned by the oxygen vacancies created during reactive DC sputtering

Tungsten oxides are interesting for a variety of applications due to their versatile optoelectronic charac-teristics,which can be tuned changing the composition and/or the crystalline structure.Coloration due to sub-bandgap absorption is often achieved by ion intercalation or doping in WO3:M films(with M=H+,Li+,Na+,etc.introducing extra electrons),but a more direct way is creating charged oxygen vacancies(Vo+and/or Vo2+)in sub-stoichiometric WO3-x forms.Here,amorphous WO3-x thin films are obtained by reactive DC sputtering of a pure W target,on unheated glass substrates,changing the oxygen to argon pressures ratio.The control of intrinsic defects(oxygen vacancies and tungsten valence states)by the oxy-gen partial pressure allows tuning the morphology,sub-bandgap absorption and carrier density in these WO3-x films,as it is proven by Raman spectroscopy,atomic force microscopy,optical spectrophotometry and Hall effect measurements.     

基于声辐射模态的粘弹性阻尼板声功率最小化研究*

为了减小薄板结构振动辐射的噪声,在重量约束下进行了声功率最小化研究。利用有限元振动模型来处理结构振动环节,利用声辐射模态模型来处理声辐射环节,用可行方向法进行了优化设计研究。以一矩形粘弹性阻尼板为例,得到了阻尼重量约束下板的声功率最小化模型,结果表明在满足重量约束条件下能够达到明显的降噪效果。     

Analysis of optical sensing behavior of a novel optical bean-shaped resonator biosensor integrated with MZI configuration

A novel optical bean-shaped resonator (BR) biosensor integrated with Mach–Zehnder Interferometer structure based on a silicon-on-isolator platform has been proposed and investigated theoretically and numerically. By characterizing and optimizing the structure, our bean-shaped device exhibits a high extinction ratio over 50?dB and a high Q factor of about 5.46?×?10⁴ in a wide wavelength span. The quasi-free spectral range (FSR) is about 469?nm. The sensitivity of 688.6?nm/refractive index unit (RIU) is achieved for bulk changes of refractive index and the detection range varies from 10^?6 to 0.689 RIU. More complex bean-shaped structures can also be cascaded by adding more bending waveguides in BR to obtain wider quasi-FSR range.     

Analysis of acoustic resonator with shape deformation using finite element method

An acoustic resonator with shape deformation has been analysed using the finite element method. The shape deformation is such that the volume of the resonator remains constant. The effect of deformation on the resonant frequencies is studied. Deformation splits the degenerate frequencies.     

Chirped bright and double-kinked quasi-solitons in optical metamaterials with self-steepening nonlinearity

Considering the self-steepening effect in a metamaterial (MM) can significantly change its behaviour. We study the propagation of ultrashort pulses in nonlinear MMs that is governed by a generalized nonlinear Schrö dinger equation with higher order effects such as pseudo-quintic nonlinearity and self-steepening effect. A class of chirped quasi-soliton solutions is obtained in the presence of the self-steepening term, and some of which are derived for the first time. The solutions comprise chirped bright quasi-solitons on a constant and zero background, kink and anti-kink quasi-solitons, and double-kink quasi-solitons. It is found that the nonlinear chirp associated with each of these waves is directly proportional to the intensity and its amplitude can be controlled by selecting the self-steepening and dispersion coefficients. Particular cases of chirp-free quasi-solitons are discussed. The conditions on MM parameters for the formation of these structures are also presented. The obtained results are important to explore much richer localized light pulses in MMs.     

深圳某冰蓄冷中央空调系统运行模式及控制方式分析

以某冰蓄冷中央空调系统为例,详细分析冰蓄冷中央空调系统的几种运行模式及相应的控制方式,合理的控制方式能够最大限度地降低冰蓄冷中央空调系统的运行费用。     

Design of magnetorheological damper with a combination of shear and squeeze modes

Magnetorheological (MR) damper is a semi-active suspension device that uses MR fluid to produce controllable damper. The mechanical properties of the suspension can be controlled by adjusting the yield stress of MR fluid. This paper presents the design of a new concept for MR damper with a combination of shear and squeeze working modes. Finite Element Method Magnetics (FEMM) was utilized to simulate the magnetic field generated by electromagnetic coils in MR damper. The MR damper was designed and fabricated according to the simulation results. The experimental tests were performed under quasi-static loading in three different conditions; shear mode, squeeze mode and combination of both modes. The results showed that the mixed mode MR damper has produced a unique damping characteristic where in general, a higher damping force has obtained in mixed mode than single mode.     

A quadrilateral mixed finite element with two enhanced strain modes

An improved plane strain/stress element is derived using a Hu–Washizu variational formulation with bilinear displacement interpolation, seven strain and stress terms, and two enhanced strain modes. The number of unknowns of the four-node element is increased from eight to ten degrees of freedom. For linear and non-linear applications, the two unknowns associated with the enhanced strain terms can be eliminated by static condensation so that eight displacement degrees of freedom remain for the proposed element, which is denoted by QE2. The excellent performance of the proposed element is demonstrated using several linear and non-linear examples.     

穿孔管消声器横截面模态及消声特性的有限元分析

将有限元法应用于计算穿孔管消声器的横截面模态频率,推导了相应的有限元公式并编写了计算程序。对于圆形同轴结构的模态频率,有限元法计算结果与解析法计算结果吻合良好,表明了有限元法预测穿孔管消声器横截面模态的准确性。之后将有限元法应用于计算和分析孔径、穿孔率和穿孔管偏移对直通穿孔管消声器横截面模态和消声特性的影响。结果表明,穿孔率低于40%时,孔径减小或穿孔率增大均能使(0,1)阶模态频率升高,消声器中频消声效果变好;穿孔率高于40%后,孔径和穿孔率对(0,1)阶模态频率影响较小。对于非同轴结构,平面波截止频率为第2阶模态频率,对于给定的孔径和穿孔率,穿孔管偏移对第2阶模态频率影响较小。     

基于假设模态法的风力机动力学分析

采用Kane方法建立风力机系统动力学模型,并使用假设模态离散化方法对其进行柔性化。结合修正的BEM理论计算得到的风轮气动载荷,并在Fortran环境下编程建立风力机整机的系统动力学数学模型,完成对风力机的随机响应分析。以某型2.5MW风力发电机组为研究对象进行分析计算,将分析数据同国际权威计算软件GH Bladed数据比较。比较表明,该分析模型可以较好的模拟风力机的动力学特性,同时兼顾了较少建模计算时间和较高分析精度两个优点,近而验证采用假设模态法进行风力机动力学分析是一种行之有效的方法。