Influence of Field Effects on the Performance of InGaAs-Based Terahertz Radiation Detectors

A detailed electrical characterization of high-performance bow-tie InGaAs-based terahertz detectors is presented along with simulation results. The local surface potential and tunnelling current were scanned over the surfaces of the detectors by means of Kelvin probe force microscopy (KPFM) and scanning tunnelling microscopy (STM), which also enabled the determination of the Fermi level. Current-voltage curves were measured and modelled using the Synopsys Sentaurus TCAD package to gain deeper insight into the processes involved in detector operation. In addition, we performed finite-difference time-domain (FDTD) simulations to reveal features related to changes in the electric field due to the metal detector contacts. The investigation revealed that field-effect-induced conductivity modulation is a possible mechanism contributing to the high sensitivity of the studied detectors.     

用于10mm 微测辐射热计的红外光学天线设计

微测辐射热计利用热敏电阻对温度的敏感特性来实现红外探测,将光学天线场局域的能力应用于微测辐射热计,可以集中入射能量至热敏电阻,提高电阻的温度响应。基于这一思想设计了一种工作在红外波段的改进型蝶形光学天线,其中心场强最高可增强83 倍。采用了多物理分析方法,结合两种常用的热敏材料(铝和氧化钒)对耦合结构的电磁特性和热学特性进行了分析。结果显示,在1000 W/m² 的入射功率密度下,铝温升可达1.85 mK,氧化钒温升0.85 mK,与同类工作相比温度响应增强了数倍。该改进型蝶形光学天线可用于微测辐射热计提升红外探测效率,在高密度红外成像器件应用中发挥作用。     

探地雷达超宽带背腔蝶形天线设计与实现

设计实现了一种中心频率为400 MHz的吸波材料填充式背腔蝶形天线,并将此天线应用于超宽带探地雷达系统,组装完成了一套400 MHz无线控制探地雷达系统样机。背腔式设计的探地雷达收发天线可以克服传统蝶形天线在H面全向辐射所带来的缺点,从而提高雷达系统的信噪比及收发天线之间的隔离度。对背腔蝶形天线的设计进行了规律性研究,总结了吸波材料填充式背腔蝶形天线系统在工程化实现时的设计经验。实际路测数据验证了所设计背腔天线在此套探地雷达系统中性能表现稳定良好。     

基于新型蝶形单元结构人工表面等离子体激元低通陷波滤波器的设计

为降低滤波器的插入损耗以及实现滤波器的小型化,该文提出一种新型具有陷波功能的人工表面等离子体激元(SSPPs)低通滤波器,该滤波器主要由新型蝶形单元结构、过渡结构以及用于实现陷波功能的叉指电容环路谐振器(IDCLLR)结构组成。新型蝶形单元结构是由一个椭圆形贴片向左右方向旋转30°构成,经过镂空处理后可以显著降低插入损耗,相比传统的矩形和椭圆形结构具有更好的色散特性,大大提高了滤波器的带内的平坦度和带外抑制能力。该文对矩形、椭圆形、梯形以及新型蝶形等不同单元结构的色散曲线进行了分析,并仿真分析了滤波器的S₂₁和S₁₁曲线,验证了新型蝶形单元结构在色散特性、插入损耗、低截止频率和带外抑制方面所具有的优势。最后,对该滤波器进行了加工和测试,测试结果表明,该滤波器仿真结果和测试结果吻合较好,表现出较好的带外抑制和带内平坦度,可以实现对特定干扰频段陷波抑制。滤波器尺寸为0.98λ₀×0.17λ₀。该人工表面等离子体激元滤波器从设计新型单元结构的角度出发,实现了良好性能的同时,实现了滤波器的小型化。     

Optical intersecting-waveguide switches with widened angle ofdeflection

Reflection type optical switches with intersecting waveguides and bow-tie electrodes are proposed. The intersection angles of these switches are widened because of the implementation of the bow tie electrodes. The guided incident mode is expanded into an infinite spectrum of plane waves. Snell's law is applied to calculate the reflection and refraction coefficients. It is analytically shown that the intersection angle can be almost doubled without remarkable adverse effects upon the extinction ratios and scattering loss. It is, therefore, anticipated that optical switches with bow-tie electrodes exhibit superior characteristics over those with straight ones     

Coplanar waveguide-fed uniplanar bow-tie antenna

The design of coplanar waveguide (CPW)-fed bow-tie antenna for the 2.4-GHz ISM band is described. A coplanar waveguide-to-coplanar strips (CPW-to-CPS) balun is used to obtain the balanced feed line for the printed bow-tie. An analysis method based on the mixed potential integral equation method is used to characterize the input characteristics of the bow-tie antenna. The numerical results obtained are in good agreement with the experimental data. Through experiments with bow-tie antennas of various extended angles, the bow-tie antenna with a 90° extended angle exhibits the widest bandwidth in the desired frequency band which has a bandwidth of 17% for a VSWR <1.5:1     

Photonic-crystal surface-emitting laser near 1.55 /spl mu/m on gold-coated silicon wafer

An InP/InGaAs-based photonic band-edge laser bonded on silicon operating near 1.55 mum is presented. A gold reflector positioned below the slab containing the active layer reduces the optical losses of the Bloch-mode resonator. As a result, a quality factor exceeding 8000 is obtained at transparency leading to a laser threshold as low as 3.4 muJ/cm²     

MacRobends of bow-tie fibres with constant curvature

The letter treats macrobends of bow-tie fibres with constant curvature, using our previously published work as the theoretical building block. In the practical case of unequal core and cladding anisotropy, there exists a single-polarisation window which shifts towards the shorter-wavelength range as the bend radius decreases. Also treated theoretically is the extinction ratio against bend orientation. Unexpectedly, it is found that, if equal core and cladding anisotropy are assumed in the theoretical analysis, then, unlike the ideal case of a straight anisotropic fibre, the differential losses virtually disappear in a bent bow-tie fibre with constant curvature.     

模拟分析具有表面等离子体效应的纳米光学天线及其阵列

基于时域有限差分方法,模拟分析了位于介质材料上的杆形和蝴蝶结形两种金纳米天线及杆形天线阵列.结果表明天线近场光斑直径约可以达到波长的1/11,蝴蝶结形天线的光斑强度可以比入射光场增强91倍.杆形天线阵列仍可以实现这种增强效应.蝴蝶结形天线中光场增强最高可以达到28000倍,而且局域化的光场町以耦合到天线臂上的纳米颗粒.     

Ground influence on the input impedance of transient dipole and bow-tie antennas

In this paper, the influence of a lossy ground on the input impedance of dipole and bow-tie antennas excited by a short pulse is investigated. It is shown that the ground influence on the input impedance of transient dipole and bow-tie antennas is significant only for elevations smaller than 1/5 of the wavelength that corresponds to the central frequency of the exciting pulse. Furthermore, a principal difference between the input impedance due to traveling-wave and standing-wave current distributions is pointed out.     

Analysis and design of broadside-coupled striplines-fed bow-tieantennas

The design of a bow-tie antenna fed by broadside-coupled striplines (BCS) for the 2.4-GHz ISM band is described. The two fins of the bow tie are, respectively, on the two sides of the substrate. The feeding balanced lines adopted are the BCS. A quarter-wave transformer is used to transform the microstrip line input to the BCS feed. An analysis method based on the mixed-potential integral equation method is used to characterize the input characteristics of the bow-tie antenna. The numerical results obtained are in good agreement with the experimental data. Through experiments with bow-tie antennas of various extended angles, the bow-tie antenna with a 90° extended angle exhibits the widest bandwidth in the desired frequency band, which has a bandwidth of 19% for a VSWR<1.5:1     

Vertical scaling of 0.25-/spl mu/m emitter InP/InGaAs single heterojunction bipolar transistors with f/sub T/ of 452 GHz

Vertical scaling of the epitaxial structure has allowed submicron InP/InGaAs-based single heterojunction bipolar transistors (SHBTs) to achieve record high-frequency performance. The 0.25/spl times/16 /spl mu/m/sup 2/ transistors, featuring a 25-nm base and a 100-nm collector, display current gain cut-off frequencies f/sub T/ of 452 GHz. The devices operate at current densities above 1000 kA/cm/sup 2/ and have BV/sub CEO/ breakdowns of 2.1 V. A detailed analysis of device radio frequency (RF) parameters, and delay components with respect to scaling of the collector thickness is presented.     

便携设备中带陷蝶形UWB天线的设计

提出了一种应用于便携设备中具有带陷特性的平面蝶形UWB天线.该天线采用蝶形贴片作为辐射单元,并由渐变线作为阻抗变换器与50 Ω馈线进行匹配.通过在辐射面上挖C形槽实现带陷功能,并给出仿真和实测结果.该天线的工作频带覆盖3.1～10.6 GHz,并有效避免了5.15～5.825 GHz的无线局域网(WLAN)频段,适于便...     

Reflection-type optical waveguide switch with bow-tie electrode

Based on the total internal reflection and the plasma dispersion effect of SiGe alloy, an intersectional rib optical waveguide switch with bow-tie electrode has been proposed and fabricated for operating wavelengths of 1.3 and 1.55 μm. The thickness of the SiGe layer is 2.6 μm and the width is 9 μm. The branch angle of the switch is 2° and the bow-tie angle is 1.5°. The crosstalks are -19.6 dB for 1.3 μm and -21.8 dB for 1.55 μm. At both wavelengths, the extinction ratio is larger than 38.5 dB and the insertion loss is less than 1.70 dB. The switching time is about 180 ns     

Bow-tie antennas on high dielectric substrates for MMIC and OEICapplications at millimetre-wave frequencies

A two-element bow-tie dipole antenna and a single-element bow-tie slot antenna fabricated on a high dielectric constant (ε_r=10.2) substrate are introduced for applications at millimetre-wave frequencies. The former antenna provides 2 GHz bandwidth at 35 GHz and the latter 1.3 GHz at 32.7 GHz. With a broadband match, these antennas would yield significantly higher bandwidths     

Microbending losses of bow-tie and similar anisotropic fibres

In the letter the microbending behaviour of bow-tie fibres is investigated theoretically. Our results for the practically existing case of unequal core and cladding anisotropy agree satisfactorily, in a statistical sense, with the published experimental data. In the ideal case of equal core and cladding anisotropy, our results confirm the prediction by Snyder and Rühl that the polarising behaviour of a long bow-tie fibre with microbends is caused by the `small field? effect. The related but different problem concerning bow-tie macrobends is treated in another letter.     

Nonvolatile Memory Effect in Indium Gallium Arsenide-Based Metal–Oxide–Semiconductor Devices Using II–VI Tunnel Insulators

This paper reports the successful use of ZnSe/ZnS/ZnMgS/ZnS/ZnSe as a gate insulator stack for an InGaAs-based metal–oxide–semiconductor (MOS) device, and demonstrates the threshold voltage shift required in nonvolatile memory devices using a floating gate quantum dot layer. An InGaAs-based nonvolatile memory MOS device was fabricated using a high-κ II–VI tunnel insulator stack and self-assembled GeO _x -cladded Ge quantum dots as the charge storage units. A Si₃N₄ layer was used as the control gate insulator. Capacitance–voltage data showed that, after applying a positive voltage to the gate of a MOS device, charges were being stored in the quantum dots. This was shown by the shift in the flat-band/threshold voltage, simulating the write process of a nonvolatile memory device.     

Genetic algorithm based inversion of neural networks applied to optimised design of UWB planar antennas

An inversion of artificial neural networks using a genetic algorithm is presented for a novel concept of optimisation applied to UWB planar antennas of bow-tie type with respect to specified values of antenna performance in the frequency range 3.1-10.6 GHz. This efficient concept is shown to achieve significant reduction in computing time for optimisation. The multidimensional inversion is characterised by a simple composite fitness or target function that includes antenna parameters as a function of signal frequency or/and angle dependence. Good impedance matching and gain performance is achieved over the whole frequency range by adequately modifying the radiating contour profile of the conventional triangular bow-tie antenna.     

2×2 optical waveguide switch with bow-tie electrode based oncarrier-injection total internal reflection in SiGe alloy

Based on the total internal reflection and the plasma dispersion effect of SiGe alloy, a 2×2 intersectional rib optical waveguide switch with bow-tie electrode has been proposed and fabricated for the wavelength of 1.3-μm operation. The thickness of the SiGe layer is 2.6 μm and the width is 9 μm. The branch angle of the switch is 2° and the bow-tie angle is 1.5°. The on-state crosstalk is -19.6 dB, the off-state extinction ratio is 38.5 dB and the off-state insertion loss is less than 1.70 dB. The switching time is about 180 ns     

线列探测器推扫成像中的锯齿拖影研究

在一种基于InGaAs材料的短波红外线列探测器中,光敏元呈品字形排列。在使用该探测器进行推扫成像时,图像中发现了锯齿状的拖影。这种拖影的出现降低了图像的质量。研究发现,串扰是锯齿拖影的成因,而串扰有多种来源,如探测器光敏元的光串或电串、电路的带宽不够等等。为了确定串扰的真正来源,进行了基于平行光管的单光点实验。实验观察了探测器对单光点的响应,实验结果表明这种锯齿拖影是探测器读出电路的带宽不够造成的。在改进了探测器读出电路的性能后,消除了图像中的锯齿拖影。