Terahertz oscillations in semiconducting carbon nanotube resonant-tunneling diodes

The paper presents the simulation and possible physical implementation of a resonant tunneling diode based on a semiconducting single-walled carbon nanotube, which exceeds the performance of similar resonant tunneling devices based on semiconductor heterostructures. In this respect, the oscillation frequency and the output power are predicted to be greater by one order of magnitude, attaining 16 THz and 2.5 μW, respectively. The generated THz signal is directly radiated into free-space through the injection contacts of the resonant tunneling diode, which have the shape of a bowtie antenna.     

Influence of N cluster states on band dispersion in GaInNAs quantum wells

We use a modified band-anticrossing (BAC) model to investigate the band dispersion in a GaN_xAs_1-x/AlGaAs quantum well (QW) as a function of hydrostatic pressure. The band edge mass increases considerably more quickly with pressure than in the case of a GaAs/AlGaAs QW, and the subband separation also decreases significantly. We predict that the strong anticrossing interaction between the GaAs host conduction band and isolated N levels will inhibit tunnelling through the QW for a range of energy above the isolated N levels. The energy of N resonant states depends strongly on details of the local environment, giving a broader calculated distribution of N states in GaInNAs compared to GaNAs.     

Silicon-on-insulator microcavity light emitting diodes with two Si/SiO2 Bragg reflectors

Light emitting pn-diodes were fabricated on a 5.8 μm thick n-type Si device layer of a silicon-on-insulator (SOI) wafer using standard silicon technology and boron implantation. The thickness of the Si device layer was reduced to 1.3 μm, corresponding to a 4λ-cavity for λ=1150 nm light. Electroluminescence spectra of these low Q-factor microcavities are presented. Addition of Si/SiO₂ Bragg reflectors on the top and bottom of the device (3.5 and 5.5 pairs, respectively) is predicted to lead to spectral emission enhancement by ∼270.     

固体FTIR光声光谱的共振增强

我们在FTIR光声光谱测量工作中首次观察到由光声池频率响应特性造成的光声信号共振增强现象.研究表明,这种效应起源于样品腔中气体传声器对声压信号的响应不平坦.文中讨论了利用此效应提高光声检测灵敏度和信噪比的可能性,并且给出了一个利用共振增强方法研究导电聚合物PTh样品中SP_3结构缺陷的实例.     

准对称流的混沌和共振流线

采用计算Melnikov函数的方法 ,研究了描述qth(q=3或 6 )准对称流流体粒子运动的动力系统 .文中在分析未扰动系统轨道解析表示的基础上 ,深入考察了扰动系统的分岔情况 .结果表明 ,扰动系统在一定条件下能够分支出混沌和共振流线 .     

过模慢波结构频率反射特性及谐振腔的影响

 利用有限元方法求解:S-参数矩阵，研究了过模慢波结构对圆波导TM₀₁，TM₀₂模的反射特性，分析了在慢波结构末端加入谐振腔后，由于两端口的不对称性而造成的对反射特性影响。结果表明，在TM₀₁的π模频率附近，慢波结构和谐振腔组成的系统对无谐振腔一侧端口入射TM₀₁模的反射增大，而对有谐振腔一侧端口入射TM₀₁模的反射减小。根据计算结果，解释了普通多波切伦柯夫振荡器所用慢波结构周期数较多的原因，说明了在多波切伦柯夫振荡器中引入谐振腔后，不但可以减少所用慢波结构周期数，而且有利于提高微波输出效率。     

对数比电路原理与低频工作点反馈系统

 在合肥光源注入系统升级改造后，尝试了几种方法来改进机器注入束流稳定性。研制了用于抑制注入过程残余β振荡的水平和垂直方向的工作点振荡抑制模块，尝试了包括逐圈测量和锁相环原理来激励和稳定束流等方法来跟踪工作点变化。详细分析了基于对数比原理的逐圈测量系统，包括单束团和多束团模式，证明在多束团模式下逐圈测量的可行性和意义，更新了数据采集和可远程控制的软件集成环境。     

以多胺为探针的DNA共振光散射光谱法测定

研究了三种常见多胺与小牛胸腺脱氧核糖核酸(DNA)作用的共振光散射光谱.发现在pH 2.21～9.15的B-R缓冲溶液中,小牛胸腺DNA与精胺的结合产生强烈的共振光散射,散射强度在343 nm波长处达到最大.小牛胸腺DNA的质量浓度在0.1～40 mg·L-1范围内与共振光散射强度呈线性关系,回归方程的相关系数为0.998 9,检出限为19μg·L-1.5倍于DNA浓度的蛋白质、核苷酸都不干扰DNA的分析测定,金属离子的允许浓度一般为1.0×10-6mol·L-1.     

Resonant frequencies and quality factors in lossy NRD cylindrical resonators

In this paper the fundamental effects of losses on resonant parameters (frequencies and quality factors) are analyzed for circular-cylindrical dielectric resonators inserted between metal plates, in the configuration also called NRD (Non-Radiative Dielectric).Power dissipations are considered both in the dielectric and in the conductors. Complex resonant frequencies and closed-form expressions for the relevant quality factors are derived rigorously for arbitrary resonant modes, even without circular symmetry. Numerical results are presented and discussed, making also use of experimental data obtained by means of a suitable NRD set-up.The present analysis accurately provides the basic information for a more realistic design of up-to-date millimeter-wave frequency-selective devices in NRD circuitry.