Parametric instability in a nanoelectromechanical detector of modulated terahertz radiation on the basis of a high electron mobility transistor with a mobile elastic gate

Parametric instability in a modulated terahertz radiation detector based on a high electron mobility transistor with a mobile elastic gate fabricated from a conductor in the form of a micronanocantilever is studied in detail. The analysis is based on the method of coupled oscillations and subsequent testing by direct numerical integration of the original equations. The thresholds and increments of the instability are determined. The feasibility of practical realization of conditions for parametric instability in such detectors is discussed.     

外场下等离子体中波的增强和带电粒子流的加速

在不考虑碰撞机制的情况下,研究了外加高频电磁场(泵波)下等离子体中Langmuir波和离子声波的增强以及带电粒子流的加速.基于流体力学方程,推导了描述等离子体参量不稳定性的振动方程,进一步得到描述带电粒子流加速的数学表达式和有质动力的数学表达式.结果表明,在等离子体参量不稳定性的激发过程中,Langmuir波和离子声波得以增强以及带电粒子流由于泵波与Langmuir波(离子声波)的耦合而加速;有质动力的产生是由于泵波与Langmuir波(离子声波)的耦合而且它是参量不稳定过程的策动力,另外有质动力不仅存在高频分量,还存在低频分量.     

Coupled-mode theory

The authors give a brief historic perspective of the coupled mode theory. The development and applications of the theory in microwaves in early years and in optoelectronics and fiber optics in recent years are described. They then consider lossless coupling of two modes in time. Two coupled resonance circuits, or two coupled microwave or optical resonators, are the physical examples. The start-up of a parametric oscillator is another example. Then they look at the formal derivation of coupled mode theory and consider the more general case when the modes are not energy-orthogonal and the energies are not necessarily positive. A more detailed account of the nonorthogonal coupled mode theory developed in the last five years for optical waveguides is given     

Pyroelectric detector coupled with ultrasonic parametric amplifier

It is pointed out that responsivity can be improved by mechanical resonances. The enhancement factor of responsivity of a trigricyne sulphate (TGS) pyroelectric detector is measured as 40 ∼ 50 at the mechanical resonances whose modes are assigned to dilational modes of a rectangular-plate vibrator. Also, a pyroultrasonic parametric amplifier is demonstrated, which can show further improvement of responsivity of the pyroelectric detector by amplifying the strain that accompanies pyroelectricity. Gain and an equivalent circuit are derived using a simplified parametrically coupled multimode vibrator model. A pyroultrasonic parametric amplifier using lead zirconate titanate (PZT) ceramic is demonstrated, and an improvement of about 5 dB is shown. Obtaining the gain stability is one of the serious problems of a pyroultrasonic parametric amplifier.     

Inverse eigenvalue sensing with corner coupled square plate MEMS resonators array

Monitoring the collective behaviour of coupled micro/nano resonators array provides a distinct opportunity for high resolution multi-function sensing. We report an inverse eigenvalue analysis based sensing approach for large array of coupled micro/nano resonators. A new characterization algorithm is proposed to precisely extract the system matrix of those multiplexed sensors with reduced algorithmic complexity and below 1% relative error. The method has been verified experimentally using five corner coupled square plate MEMS resonators with a natural frequency close to 0.85 MHz. The method is also capable of characterizing the fabrication process and important sensor parameters such as the spring constant and coupling ratio.     

Modes in Coupled Optical Resonators with Active Media

A general method is proposed to analyze the properties of optical systems composed of several coupled resonators. It is shown that by using appropriate matrices to represent the fields in the resonators and the couplings between them, an equation can be written, often by inspection, for the eigenvalue s=/spl sigma/+j/spl omaga/ which gives the frequency and the rate of growth of the fields for all the modes of a given system. A re-entrant coupled system with loss and gain regions is discussed as an example. The effects of changes in mirror transmission, resonator length and medium properties are studied using the method.     

Design of resonators from sections of irregular transmission lines

The problem of minimization of the difference in the characteristic impedances of resonators designed from sections of smoothly irregular and stepwise irregular transmission lines, which have distributions of initial eigenfrequencies important for practice, is solved. This problem is solved using the parametric synthesis method in which resonator eigenfrequencies are used as independent variables. It is shown that stepwise irregular resonators have lesser differences in the characteristic impedances than smoothly irregular resonators. A characteristic feature of synthesized resonators, their tendency to most simple shapes, is found. A set of synthesized stepwise irregular resonators is presented and their main characteristics are described. Using features of the obtained solutions, a simple method for the design of stepwise irregular resonators with minimum difference in the characteristic impedances is proposed, which allows one to expand in future the set of resonators suitable for practical applications.     

Bandpass characteristics of coupled resonators

A system of series-coupled transmission cavity resonators formed from sections of regular waveguides separated by coupling windows is considered. Bandpass characteristics of this system are obtained by representing the fields in the cavities in the form of a sum of the waves scattered by the windows. A method for measuring the intercavity coupling coefficient for two coupled resonators is presented and a good agreement between the calculated and measured characteristics is demonstrated.     

腔光力系统中声子的朗道-芝诺-斯塔博格干涉（特邀）

微纳机械振子被认为是一种发展片上信号处理器件的理想平台,可以将各种不同的物理场转换为振动声子,实现基于声子的片上信息处理。其中,控制声子在不同机械振子间的传输是实现声子信息处理的关键。通过将两个机械振子耦合构造两模机械系统,目前虽然已经实现了不同杂化模式间声子的相干传输,但是依然缺乏直接调控两个独立机械振子有效耦合强度的方法。为此,文中在腔光力系统中开发了基于朗道-芝诺-斯塔博格（Landau-Zenner-Stückelberg,LZS）干涉的相干声子操控方法。在利用光学囚禁作用调控两个机械振子振动模式杂化的基础上,通过对囚禁光进行调制施加参量驱动场,使得系统周期性地穿过免交叉点实现了声子的LZS干涉。研究表明:在满足共振条件下,利用LZS干涉可以实现声子在两个独立机械振子间的相干传递。笔者的研究为实现声子信息在实空间的高效传递提供了一个有效途径。     

压电谐振式矿用甲烷传感器探头设计与研制

设计一种用于甲烷浓度监测的基于压电陶瓷谐振的传感器探头。利用有限元分析软件辅助设计2种具有较大吸附面积的谐振体;分别以5A型沸石分子筛和活性炭修饰谐振体,构成4种传感器敏感探头;利用自行搭建的测试平台在甲烷体积分数为0⁷.6%间对不同敏感探头阻抗谱谐振峰偏移量灵敏度与线性度的对比分析,结果表明,以5A型沸石分子筛与板状谐振体组合得到的探头在爆炸浓度下限谐振峰偏移162Hz,具有较好的灵敏性;由活性炭与环状谐振体组合得到的探头在爆炸浓度下限以下具有良好的线性。     

Shorted two-dimensional high-Tc Josephson arrays for oscillator applications

We present results of our experimental investigations of the dynamic properties of two types of shorted two-dimensional (2D) arrays. The first type consisted of 4×4 YBCO step edge junctions integrated into a circuit, which allowed the simultaneous detection of all single row voltages. Thus, using only dc-measurements, the interaction and synchronization between the rows could be observed. In the second investigated array type the edge junctions of the rows were closed into superconducting loops in the form of coplanar resonators. Resonant steps were observed on the current–voltage characteristic due to interaction of the junctions with the resonators. The circuits were integrated into a stripline geometry and coupled to another (detector) Josephson junction. A clear detector response, i.e. Shapiro steps, was measured up to 460 GHz. Steps up to 4th harmonic were observed in the frequency range 150–200 GHz.     

UR90腔相干并束输出的实验研究

用多个UR90腔进行正向模耦合的方法来产生多束相干的激光 ,解决了反向模耦合中存在的失谐问题 ,可以大大提高系统的可靠性。并利用铜蒸气激光器实现了两台低放大倍率 (M =1 2 1)UR90腔的相干并束输出 ,对输出光束的远场方向性进行了测量分析。结果表明 ,和以前单台UR90腔相比 ,此方法对UR90腔的模控能力和输出光束的光束质量并没有明显影响 ,是一种简单而有效的耦合方式。     

A general eikonal treatment of coupled dispersively nonlinear resonators exhibiting optical multistability

A recently presented eikonal treatment of nonlinear resonators is reformulated so as to enable a straightforward generalization to coupled resonators. A few coupled dispersively nonlinear resonator configurations are presented and analyzed. They exhibit novel types of multistability.     

Controlling the Bandwidth of Split Ring Resonators

A method to control the half-power relative band- widths of split ring resonators (SRRs) coupled to a transmission-line system is presented. An equivalent circuit model is proposed to analyze the main factors that effect the relative band- widths of SRRs. Based on the analysis, we propose an efficient way to control the relative bandwidth of SRR, which has been verified by both full-wave simulations and experiments. The proposed analysis can be used to design novel resonators and other microwave components.     

Characteristics of single and coupled rectangular resonators in suspended substrate stripline

A rigorous spectral-domain analysis is carried out to determine the resonant frequency characteristics of resonators in a general suspended substrate stripline. The resonant frequency characteristics of single as well as coupled rectangular resonators are computed. An important observation for resonators in broadside-coupled suspended substrate stripline is that the even- and odd-mode resonant frequencies are considerably different.     

低插损同轴型微波介质滤波器的设计

1/4波长同轴谐振器构成的微波介质带通滤波器,具有三个谐振孔、二个耦合孔,谐振器间通过耦合孔相互耦合,材料采用高介电常数微波陶瓷,器件表面涂覆金属电极。讨论了耦合孔半径对滤波器技术指标(中心频率f_0、3dB带宽B、插入损耗L_0、阻带抑制L_A等)的影响,然后根据给定的滤波器技术指标确定了滤波器的类型、结构、级数及尺寸,最后进行了仿真验证,得到了低损耗的带通滤波器。     

异构耦合谐振器耦合系数的提取

为寻找异构耦合谐振器耦合系数提取电路的设计原则,本文将提取同构耦合谐振器耦合系数的电路模型一般化,在电路仿真软件中分析其各项参数变化对特征频率的影响方式,从中总结异构耦合谐振器耦合系数提取电路的设计原则与注意要点。设计了一对特定异构耦合谐振器耦合系数的提取电路,通过其提取的耦合系数在一个双频带带通滤波器设计中发挥了重要...     

Modulating the Near Field Coupling through Resonator Displacement in Planar Terahertz Metamaterials

We present the effect of vertical displacements between the resonators inside the unit cell of planar coupled metamaterials on their near field coupling and hence on the terahertz (THz) wave modulation. The metamolecule design consists of two planar split- ring resonators (SRRs) in a unit cell which are coupled through their near fields. The numerically simulated transmission spectrum is found to have split resonances due to the resonance mode hybridization effect. With the increase in displacement between the near field coupled SRRs, this metamaterial system shows a transition from coupled to uncoupled state through merging of the split resonances to the single intrinsic resonance. We have used a semi-analytical model describing the effect of displacements between the resonators and determine that it can predict the numerically simulated results. The outcome could be useful in modulating the terahertz waves employing near field coupled metamaterials, hence, can be useful in the development of terahertz modulators and frequency tunable devices in future.     

一种双圆柱腔微波加热系统的仿真研究

本文提出并设计了一种工作频率为2．45GHz的双圆柱腔微波加热系统。该加热系统是在矩形波导宽边中央开孔,用两支铜棒将矩形波导中传输的微波耦合到双圆柱腔内并对圆柱腔内的化学反应罐进行加热。仿真研究表明,通过调节短路活塞、耦合铜棒和调配螺钉,在主要工作频带内输入端反射系数小于-10dB,耦合进两个圆柱腔内的功率相等,两个圆柱腔内场分布大致相同。此双圆柱腔微波加热系统具有效率高、加热均匀等特点,在微波化学分析中具有较好的应用前景。     

A Ferrimagnetically-Tuned Parametric Amplifier

A parametric amplifier can normally be tuned only over relatively restricted frequency ranges. One of the basic reasons for this tuning difficulty is that more than one frequency range is of importance for, in addition to the signal frequency, a pump frequency and one or more sum or difference frequencies must be considered. In this paper a tunable negative-resistance parametric amplifier is described which uses ferrimagnetically-tuned signal and idler circuits, together with a fixed-frequency pump source. This amplifier is unique in two respects. One is that the amplifier is electrically tuned through the use of yttrium iron garnet (YIG) resonators. Secondly, useful low-noise performance has been achieved over a tuning range of almost one octave, this amplifier thus successfully demonstrates that the technique of magnetic tuning with YIG resonators can be applied to a device as complex as a parametric amplifier in much the same manner as it has been applied in the past to microwave band-pass and band-stop filters.