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在理想条件下,为了研究等离子体参数、填充率、入射角度和介质层相对介电常数对一维三元磁化等离子体光子晶体的禁带特性的影响,用由传输矩阵法计算得到的TE波任意角度入射时的左旋极化波(LCP)和右旋极化波(RCP)的透射系数来研究其禁带特性。结果表明,仅增加等离子体碰撞频率不能实现禁带宽度的拓展,改变等离子体频率、填充率和介质层的相对介电常数能实现对禁带宽度和数目的调谐。改变等离子体回旋频率能实现对右旋极化波的禁带的调谐,但对左旋极化波的禁带几乎无影响。入射角度的增大使得禁带低频区域带宽变大,而高频区域带宽则是将先减小再增大。     

一种介质-金属加载圆孔单元厚屏频率选择表面

厚屏频率选择表面能较好地改善FSS带宽性能,是实现隐身雷达天线罩的有效手段.为了全面掌握厚屏FSS的传输特性,给FSS的工程应用提供可靠依据,本文设计了一种介质-金属加载圆孔单元的厚屏频率选择表面.采用矩量法对此结构进行分析计算,主要研究了加载金属直径、加载介质厚度、电磁波入射角等几个参数对厚屏FSS传输特性的影响规律.仿真实验结果表明:带宽、中心频率及其透过率都对填充介质直径、加载金属直径、加载介质厚度、电磁波入射角和不同排列方式有不同程度的敏感性,可以通过合理调整加载金属直径及加载介质厚度来获得较宽的通带和较高的透过率.这为实现厚屏FSS在曲面隐身雷达天线罩上的应用提供了一种有价值的借鉴.     

2维光子晶体中的掺杂效应数值研究

 把平面波展开方法(PWM)用于2维光子晶体掺杂情况下透射特性的研究,计算得到了粗细不同的空气柱掺杂、相同半径不同介质柱掺杂、不同柱体形状掺杂情况下2维光子晶体的透射系数与入射光频率的关系曲线。结果表明2维光子晶体的禁带的宽度、位置、透过率与掺杂体半径、掺杂体介电常数、掺杂体柱体几何形状等因素有关,掺杂因素相差越大透射曲线变化越明显,特别是损耗介质的掺入更使得禁带可调要素增加。     

磁导率对二维蜂窝结构光子晶体带隙的影响

利用平面波展开法对二维六角晶格结构磁性光子晶体的带隙特性进行了研究,给出其能带结构分布图,并与非磁性介质构成的光子晶体进行了比较.结果表明,由磁性材料构成的光子晶体更易出现带隙,磁导率对带隙结构影响很大.空气背景磁性散射子情况,磁导率增加较小时,二个绝对光子带隙宽度逐渐减小,直至消失.继续增加磁导率,在较低频率范围内出现一个绝对光子带隙,占空比逐渐加大,且最佳填充系数基本保持不变.磁性背景空气散射子,类似地在较低频率范围内也出现了一个绝对光子带隙.磁性背景非磁性散射子与空气背景磁性散射子情况相似.     

Defect and dope selective of transmission properties of 2D photonic crystal

The effects of the defect and doping on the transmission properties are investigated in two-dimensional photonic crystal (PC) with triangular rods using the finite difference time domain (FDTD) method. The results show that the width and the central position of the photonic band gap (PBG) depend on the thickness of rods with defect or composite-defect, and the refractive index of doped dielectric rods. The transmission properties of composite-defect combined with doping are further investigated. The thinner the nested concentric triangular rod and the smaller the refractive index is, the wider the band gaps is.     

Photonic band gap engineering in 2D photonic crystals

The polarization-dependent photonic band gaps (TM and TE polarizations) in two-dimensional photonic crystals with square lattices composed of air holes in dielectric and vice versa i.e., dielectric rods in air, using the plane-wave expansion method are investigated. We then study, how the photonic band gap size is affected by the changing ellipticity of the constituent air holes/dielectric rods. It is observed that the size of the photonic band gap changes with changing ellipticity of the constituent air holes/dielectric rods. Further, it is reported, how the photonic band gap size is affected by the change in the orientation of the constituent elliptical air holes/dielectric rods in 2D photonic crystals.     

二维三角柱光子晶体的传输特性

利用时域有限差分方法对二维三角介质柱光子晶体的传输特性进行了研究,计算了不同晶格、同一晶格柱体截面面积不同、放置方位角不同、入射波入射方向不同时光子晶体的传输特性。结果表明:光子禁带的宽度与中心频率和晶格结构有很大关系,三角晶格更易形成平坦光子禁带,柱体截面面积大,则形成的禁带较宽,在其他因素相同的条件下柱体放置的方位角在一定范围内对光子禁带有重要影响;对不同入射方向时光子晶体的传输特性的研究结果表明,在低频范围内,入射角对禁带宽度和中心频率没有任何影响,在高频段,透射率随入射角变大而降低。研究结果为实验上制作三角柱光子晶体器件提供了重要的理论依据。     

Influence of Kerr nonlinearity on the band structures of two-dimensional photonic crystals

Dynamic modifications of the band structures of two-dimensional photonic crystals composed of Kerr-nonlinear dielectric rods in air forming hexagonal, square and honeycomb lattices are investigated. Calculations are carried out by the method based on the finite-difference time-domain (FDTD) technique for both TM and TE polarizations. The bands in all cases are observed to red-shift with the introduction of nonlinearity. Inspection of the variation of the mid-gap frequencies with source intensity reveals that the red-shift increases as gap number increases, in a manner proportional to the mid-gap frequency in linear regime. The red-shift of mid-gap frequencies is also found to follow the adopted saturable model for the change of relative permittivity with source intensity. Either the so-called dielectric or the air band edges of the gaps are found to be more sensitive to nonlinearity resulting in broadening or shrinking of the gaps. Possible utilizations of the present observations for all-optical device applications, such as wavelength multiplexing, are discussed.     

Dispersion characteristics of two-dimensional unmagnetized dielectric plasma photonic crystal

This paper studies dispersion characteristics of the transverse magnetic (TM) mode for two-dimensional unmagnetized dielectric plasma photonic crystal by a modified plane wave method. First, the cutoff behaviour is made clear by using the Maxwell--Garnett effective medium theory, and the influences of dielectric filling factor and dielectric constant on effective plasma frequency are analysed. Moreover, the occurence of large gaps in dielectric plasma photonic crystal is demonstrated by comparing the skin depth with the lattice constant, and the influence of plasma frequency on the first three gaps is also studied. Finally, by using the particle-in-cell simulation method, a transmission curve in the \Gamma -X direction is obtained in dielectric plasma photonic crystal, which is in accordance with the dispersion curves calculated by the modified plane wave method, and the large gap between the transmission points of 27~GHz and 47~GHz is explained by comparing the electric field patterns in particle-in-cell simulation.     

Parasitic effects of air-gap through-silicon vias in high-speed three-dimensional integrated circuits

In this paper,ground-signal-ground type through-silicon vias(TSVs) exploiting air gaps as insulation layers are designed,analyzed and simulated for applications in millimeter wave.The compact wideband equivalent-circuit model and passive elements(RLGC) parameters based on the physical parameters are presented with the frequency up to 100 GHz.The parasitic capacitance of TSVs can be approximated as the dielectric capacitance of air gaps when the thickness of air gaps is greater than 0.75 μm.Therefore,the applied voltage of TSVs only needs to achieve the flatband voltage,and there is no need to indicate the threshold voltage.This is due to the small permittivity of air gaps.The proposed model shows good agreement with the simulation results of ADS and Ansoft's HFSS over a wide frequency range.     

装置参数对狭缝天线激发的等离子体表面波传播的影响

采用时域有限差分法对矩形结构装置的等离子体表面波传播进行了三维数值模拟.研究了装置参数(如介质板相对介电常数、厚度以及介质板上方空气间隙)对天线阵列激发的等离子体表面波传播的影响,给出了合适的介质板相对介电常数和厚度,并指出空气间隙的存在会严重削弱天线阵列对表面波的激发.计算结果可为大面积矩形表面波等离子体源装置的优化设计提供参考. 关键词： 时域有限差分法 等离子体表面波 狭缝天线     

Effects of dielectric core and embedding medium on plasmonic coupling of gold nanoshell arrays

The effects of the dielectric core and the dielectric embedding medium separately on transmission spectra and plasmon resonance properties of gold nanoshell arrays were investigated by using the finite-difference time-domain (FDTD) theory. It is found that when the hollow nanoshell arrays are placed in air, the wide photonic band gap becomes narrower as the core dielectric constant increases. On the contrary, when the nanoshell arrays with dielectric core are placed in the dielectric medium, the photonic band gap becomes wider. Furthermore, increasing core or medium dielectric constant leads to a redshift of the transmission spectra due to the polarization of the dielectric. Based on the electric field distributions, we also clearly show that the plasmon properties of the nanoshell arrays are strongly influenced by the presence of the dielectric.     

天线罩电厚度与材料电参数六端口测量系统设计

 介绍了一个可用于天线罩电厚度与介质材料介电常数测量的六端口反射计系统,它由对称波导五端口结与定向耦合器组成,其关键部件波导五端口结用HFSS软件仿真与设计。介绍了天线罩相对电厚度复反射系数的测量方法。用该系统对滑动短路器复反射系数进行了测量,测量结果表明,系统工作稳定,测试精度高。利用短路波导法测量了材料介电常数和损耗角正切,测量结果显示：介电常数测量的精度和稳定度较高,损耗正切的测量误差较大。     

Direction and frequency filter basing on an ultra-compact structure consisting of dielectric films

The transmission properties of a two-period structure consisting of dielectric layers and air layers are studied by numeric methods. On the condition of total reflection from dielectric to air layer, the coupling of the evanescent waves in air layers and propagation waves in dielectric layers forms some special transmission bands. Given proper structure parameters, one incident direction only allows one transmission frequency; on the other hand, one transmission frequency only allows one incident direction. This structure can simultaneously achieve frequency filtering and direction filtering.     

Anomalous dispersion in one-dimensional plasma photonic crystals

The anomalous dispersion in one-dimensional plasma photonic crystals (1-DPPCs) is studied. The width of band pass and band gap are compressed, the phase velocity decreases and the cup-off frequency comes close to the frequency of plasma when EM wave oblique incidence on 1-DPPCs. The band gaps are affected by the thickness of plasma, the dielectric constant of the dielectric material, the plasma density and the angle of incidence. Superluminal negative group velocity is discovered in this study. This character is interesting for scientists and may have a potential application.     

Al nanogrid electrode for ultraviolet detectors

Optical properties of Al nanogrids of different pitches and gaps were investigated both theoretically and experimentally. Three-dimensional finite-difference time-domain simulation predicted that surface plasmons at the air/Al interface would enhance ultraviolet transmission through the subwavelength gaps of the nanogrid, making it an effective electrode on GaN-based photodetectors to compensate for the lack of transparent electrode and high p-type doping. The predicted transmission enhancement was verified by confocal scanning optical microscopy performed at 365 nm. The quality of the nanogrids fabricated by electron-beam lithography was verified by near-field scanning optical microscopy and scanning electron microscopy. Based on the results, the pitch and gap of the nanogrids can be optimized for the best trade-off between electrical conductivity and optical transmission at different wavelengths. Based on different cutoff wavelengths, the nanogrids can also double as a filter to render photodetectors solar-blind.     

液晶调制的光子晶体可控偏光片和光开关

与介质柱型光子晶体相比，空气孔光子晶体更易于制作和集成而更有应用价值.采用平面波展开法证实了填充液晶的二维三角形分布的空气孔光子晶体方向能隙的可调节性.数值模拟结果表明：1)通过外界电场控制空气孔中所填充的相列液晶的方向可以对光子晶体的方向能隙进行调节，这种可调节性可用于制作场敏偏光片.这与Liu等人研究介质柱型光子晶体的结论相类似；2)用phenylacetylene型液晶替代5CB液晶作为填充物质所得到的空气孔光子晶体偏光片可使用的频率范围显著增大.在此基础上，还研究了填充液晶的光子晶体波导传输谱线的可调节性对特定波长的光切断和开通控制的原理，实现了与以往光开关原理不同的光子晶体光开关. 关键词： 光子晶体 液晶 可调节性 平面波展开法 场敏偏光片     

频率选择表面天线罩研究现状与发展趋势

由于雷达天线系统自身工作的特点, 他必须保证自身雷达波的正常接收和发射, 常用的隐身措施无法简单地在雷达天线隐身中获得应用. 采用频率选择表面 (FSS) 技术与天线罩技术相结合形成FSS天线罩, 可以使天线罩获得频率选择的功能. 即FSS天线罩对雷达的工作频段提供带通的传输特性, 同时改变雷达工作频段以外的雷达散射截面 (RCS) 特性, 可以实现带外隐身. 本文分析了FSS天线罩制备的基本思路, 综述了国内外FSS天线罩在结构设计、制造工艺等方面的研究状况, 并从多频FSS天线罩、智能FSS天线罩、厚屏FSS天线罩、 微型化FSS天线罩以及各技术的组合等方面对FSS天线罩的发展进行了展望. 关键词： 频率选择表面(FSS) 多频FSS天线罩 智能FSS天线罩 厚屏FSS天线罩     

Correlation between single-cylinder properties and bandgap formation in photonic structures

The origin of frequency gaps in the dispersion relation of periodic, quasi-periodic, and random photonic structures consisting of different arrangements of dielectric cylinders has been investigated. For TM polarization it was found that the formation and properties of gaps are strongly affected by Mie resonances of a single cylinder. Both the spectral position and size depend on the properties of this single scatterer. In contrast, for TE polarization no correlation between the scattering properties and bandgap formation was found, as Mie resonances are spectrally not well separated. For the inverted structure consisting of air cylinders in a dielectric material, the frequency gaps depend on the spatial arrangement of the cylinders because no pronounced Mie resonances exist in this case.     

横磁模式下二维非磁化等离子体光子晶体的线缺陷特性研究

采用等离子体的分段线性电流密度卷积时域有限差分算法研究了横磁波入射时具有单一线缺陷的二维非磁化等离子体光子晶体的缺陷模特性. 从频域角度分析得到微分高斯脉冲的透射系数,并讨论该光子晶体的晶格常数、介质圆柱半径、周期常数、缺陷层参数和等离子体参数对缺陷模特性的影响. 结果表明,改变周期常数、缺陷层位置和等离子体碰撞频率不会改变缺陷模的频率,改变缺陷层介质圆柱的相对介电常数、半径和缺陷层到介质层的中心距离可以在不改变禁带宽度的前提下实现对缺陷模的调节,改变晶格常数、介质圆柱半径和等离子体频率能同时实现对禁带宽度和缺陷模的调节. 关键词： 等离子体 光子晶体 缺陷模 时域有限差分算法