170 GHz兆瓦级回旋管TE25,10准光模式变换器设计

为满足聚变用170 GHz回旋管高功率输出和高效率传输的要求,需将高阶工作模式TE_25,10转换为高斯波束;针对这一技术需求,完成了170 GHz、TE_25,10模式高效准光模式变换器的设计,准光模式变换器由辐射器和镜面系统组成。基于几何光学和耦合波理论,完成了Denisov型辐射器相关设计;基于矢量衍射定理和相位校正算法,设计了由一个抛物面镜面、一个准椭圆镜面及一个相位校正镜面组成的镜面系统;使用Surf3D软件对辐射器进行了优化和计算,使用三维全波仿真软件FEKO对镜面系统进行了优化和计算,主要对辐射器微扰幅值、位置分布及相位差进行了优化。所设计准光模式变换器系统的能量转换效率约为95.2%,波束在输出窗处的标量高斯含量约为97.6%,矢量高斯含量约为91.8%,达到了回旋管的应用要求。     

基于圆波导缝隙的双极化水平全向阵列天线设计

设计了一种具有水平全向辐射特性的双线极化圆波导缝隙阵列天线。利用双模式转换器馈电，以提供天线所需的TM₀₁及TE₀₁模式，并抑制波导内其余高次模和基模的传输；通过沿圆波导周向交错排列的矩形横缝及纵缝，分别实现垂直和水平极化；其中将横向矩形缝隙设计为平行双环结构来增加带内谐振点，进而拓展天线的工作带宽；此外，将两种缝隙沿波导轴向进行组阵，并在天线阵列末端设计了匹配结构用以减小TM₀₁模式所带来的能量反射。仿真结果表明：该天线两种极化方式电压驻波比小于2的驻波带宽为2.75 GHz～2.95 GHz,并且整个工作频段内，两种极化方式下的增益均超过7.5 dB,水平面内不圆度小于1.8 dB,可适用于气象雷达领域。     

同时输出LP01/LP11模式的布里渊少模光纤激光器研究

为了获得光纤激光器的基模LP₀₁和高阶模式LP₁₁同时输出,采用环形腔结构,少模光纤的受激布里渊散射效应和单模掺铒光纤的增益共同提供腔内放大,利用模式选择耦合器进行腔内模式间的转换,单模/少模光纤耦合器分别提供激光输出。实验结果表明,LP₀₁模式和LP₁₁模式能够同时输出,和种子光相比波长偏移均为0.12 nm,输出光谱信噪比分别为22.69 dB和74.827 dB,功率转换效率分别为4.6×10^-3%和7.827%,波长稳定性分别为0.54 nm和0.026 nm,功率稳定性分别为3.277 dB和1.262 dB。研究结果可为多输出模式光纤激光器的后续应用提供参考光源。     

圆波导TE01-TE11模式转换器设计与实现

基于耦合波理论的基础上,分析了TE01-TE11模式转换器的特性和半径渐变指数,讨论了中心轴线弯曲下的圆波导模式转换器,对中心频率33GHz的波导进行了模拟设计、仿真,在保证带宽的前提下,尽力降低转换器的长度和提高转换效率,最后达到了97．82％的转换效率,带宽达到2GHz。     

双/三模基片集成波导和共面波导混合结构滤波器设计

针对微波带通滤波器小型化、高性能的应用需求,提出使用双/三模方形基片集成波导和共面波导混合结构设计带通滤波器.通过改变双模基片集成波导中TE₁₀₂和TE₂₀₁的谐振频率和外部耦合的强弱,可实现具有近似椭圆、非对称和无传输零点响应的双模滤波器;两个相同尺寸的共面波导作为谐振器蚀刻在基片集成波导表面,与TE₁₀₂和TE₂₀₁共同形成一个通带,设计具有多样性响应的四阶滤波器.在具有非对称响应四阶滤波器的基础上,使主模TE₁₀₁频率移动到该通带附近,设计更宽带宽的五阶滤波器.并对设计的滤波器进行加工和测试.测试结果与仿真结果吻合,表明了该混合结构设计高性能滤波器方法的可行性.     

一种准光模式变换器的设计和实验

准光模式变换器是实现高功率回旋管高效输出的重要部件。该文针对140 GHz, TE_28,8模回旋振荡管研制,开展以Denisov型辐射器和3个准光镜面构成的准光模式变换器设计与实验研究。利用标量衍射法优化辐射器辐射口径处的场分布,其与理想高斯场之间的矢量相关性为96.2%;基于几何光学和高斯波束匹配方法设计了聚焦镜面与波束整形镜面,采用3维全波分析软件Surf3D获得各个镜面上及输出窗处的场分布,对所设计的镜面系统进行了仿真验证,在输出窗处获得了高斯模式含量为96.67%的输出波束,整个模式变换器的功率转换效率为93.98%。以自行研制的TE_28,8模激励器作为准光模式变换器的输入,通过对模式变换器转换性能仿真结果验证,在严格控制加工精度及装配和实验过程的基础上,完成了准光模式变换器转换性能的冷测实验。实验结果表明,设计和实验具有合理的一致性,可以作为准光模式变换器工程应用设计和验证手段。     

改进的电磁混合耦合SIW超宽阻带滤波器设计

为了提升滤波器的阻带性能,提出了一种改进的电磁混合耦合基片集成波导(Substrate Integrated Waveguide,SIW)超宽阻带滤波器的设计。首先,利用模式的本征抑制和电磁混合耦合方法,合理地设置外部馈电端口、内部耦合窗口及内部耦合圆孔阵列,抑制了频率低于TE₁₀₅和TE₅₀₁的所有高次模;其次,利用耦合槽的偏移,在中间金属层侧壁中心约为1/10腔体宽度处刻蚀耦合槽,可同时抑制TE₁₀₅和TE₅₀₁以及TE₃₀₅和TE₅₀₃模的耦合;最后,仿真结果显示,该滤波器的中心频率f₀=5.94GHz,相对带宽为3.37%,插入损耗为2.29 d B,回波损耗优于17.1 d B。当阻带宽度延伸至4.85f₀时,抑制深度优于20 d B。综上,探讨了基片集成波导超宽阻带滤波器的宽阻带抑制,有效延伸了阻带宽度,为移动通信系统进一步提升抗干扰性能奠定了技术基础。     

W波段准光模式变换器的设计

准光模式变换器是大功率输出回旋管的关键部件.采用高转换效率的准光模式变换器可以横向输出电磁波,增大收集极的尺寸,提高回旋管的输出功率,提高整管效率.该文设计的回旋管内置准光模式变换器由Denisov辐射器天线和四个反射镜组成,输入频率为94GHz,模式为TE_6,2模.采用耦合波理论分析和优化了Denisov辐射器内的场分布,并根据矢量绕射理论编制数值模拟程序计算了各个反射镜上的场分布,其输出功率转换效率达97.2%.利用三维全波仿真软件feko6.0进行对比分析,最后加工所设计的结构并内置于回旋振荡管进行热测实验,结果表明其输出场分布与理论计算结果基本一致.     

TE01弯头切比雪夫设计方法

TE01弯头在高功率微波系统装配中有着重要作用。随着高功率微波朝着高功率、大带宽方向发展,对TE01弯头提出了高功率容量、更大工作带宽的需求。传统设计方法往往存在带宽较窄,功率容量受限的问题。TE01弯头设计难点在于存在TM11简并模。本文在椭圆波导解简并的基础上,提出了TE01弯头切比雪夫设计方法。采用耦合波理论分析完成了弯头设计过程。仿真设计了Ka频段椭圆弯头结构,长半轴为7 mm,短半轴为5.25 mm。计算机仿真结果表明：模式保留效率95%以上的频率范围从32 GHz到45.1 GHz,验证了设计方法的有效性。     

Ka波段TE01模椭圆弯波导的设计

根据椭圆波导中电磁波的传播理论与耦合波理论,基于CST仿真软件,采用了有限积分法设计出了高功率、宽带宽、高效率的TE01模900过模椭圆弯波导。CST设计仿真表明在中心频率在30．5GHz处的传输效率为98．8％。传榆效率在98％以上的带宽大于2GHz。     

Characteristics of metal-ferroelectric-insulator-semiconductor structure using Sr0.8Bi2.2Ta2O9 and Sr0.8Bi2.2Ta2O9-BaZrO3 for ferroelectric gates

Characteristics of BaZrO₃ (BZO) modified Sr_0.8Bi_2.2Ta₂O₉ (SBT) thin films fabricated by sol-gel method on HfO₂ coated Si substrates have been investigated in a metal-ferroelectric-insulator-semiconductor (MFIS) structure for potential use in a ferroelectric field effect transistor (FeFET) type memory. MFIS structures consisting of pure SBT and doped with 5 and 7 mol% BZO exhibited memory windows of 0.81, 0.82 and 0.95 V with gate voltage sweeps between −5 and +5 V, respectively. Leakage current density levels of 10⁻⁸ A/cm² for BZO doped SBT gate materials were observed and attributed to the metallic Bi on the surface as well as intrinsic defects and a porous film microstructure. The higher than expected leakage current is attributed to electron trapping/de-trapping, which reduces the data retention time and memory window. Further process improvements are expected to enhance the electronic properties of doped SBT for FeFET.     

In0.52Al0.48As/In0.53Ga0.47As/In0.52Al0.48As abrupt double-heterojunction bipolar transistors

In0.52Al0.48As/In0.53Ga0.47As/In0.52Al0.48As n-p-n abrupt double-heterojunction bipolar transistors grown by molecular beam epitaxy (MBE) have been realized for the first time. DC current gains in excess of 300 have been measured on devices operated in the emitter-up configuration. DC current gains around 50 are obtained on device structures with Be+ implanted extrinsic base regions operated in the emitter-down configuration. The carrier injection and collection behavior of the abrupt InGaAs/InAlAs heterojunctions is discussed.     

Beat-frequency between measurements between C12O216and C12O218lasers

Several beat frequencies in the range below 6 GHz have been measured using a C¹²O2¹⁶laser and a C¹²O2¹⁸laser operating on several pairs of closely spaced lines in the 9.3-μm region.     

Laser4F3/2→4I9/2and4F3/2→4I13/2transitions in KY(WO4)2:Nd3+

We report the observation of lasing at 0.9137 μm and 1.3545 μm in neodymium-doped KY(WO4)2at 77 K. Transition cross sections, fluorescent line width, and branching ratios are given.     

Some new FIR laser lines of optically pumped12CH316OH,12CH316OD, and12CH3I,12CH3Br,12CD2Cl2absorption spectroscopy of water and acetonitrile

The wavelength, polarization, and output power of several lines of the optically pumped CW FIR¹²CH3¹⁶OH (methanol) and¹²CH3¹⁶OD (1-D deuterated methanol), methyl iodide, methyl bromide, and deuterated methylene chloride lasers have been determined. In addition to lines already reported in the literature, seven strong lines have been observed. Optimum performance of the laser system is achieved by means of an improved coupling of the CO2pump power into the resonator and extraction of the FIR power from the resonator. Measurements on the power absorption coefficient of water using the laser indicate thatalpha(bar{nu})rises to almost 1100 Np ċ cm^-1at 170 cm^-1, and then shows a gradual fall with an increase in frequency. A strong temperature dependence of the 200 cm^-1peak inalpha(bar{nu})is predicted, with a decrease in the frequency of maximum power absorption coefficient with an increase in temperature. The range of measurements for acetonitrile is extended to lower frequencies so as to overlap with those determined from other millimeter wave techniques. For highly power-absorbing liquids,alpha(bar{nu})is estimated to be within ± 5 percent.     

Al0.25In0.75P/Al0.48In0.52As/Ga0.35In 0.65As graded channelpseudomorphic HEMT's with high channel-breakdown voltage

A new Al_0.25In_0.75P/Al_0.48In_0.52 As/Ga_0.35In 0_.65As pseudomorphic HEMT where the InAs mole fraction of the Ga_1-xIn_xAs channel was graded (x=0.53→0.65→0.53) is described. The modification of the quantum well channel significantly improved breakdown characteristics. In addition, use of an Al_0.25In_0.75P Schottky layer increased the Schottky barrier height. Devices having 0.5 μm gate-length showed g_m of 520 mS/mm and I_max of 700 mA/mm. The gate-drain (BV_g-d) and source-drain (BV_d-s ) breakdown voltages were as high as -14 and 13 V, respectively. An f_T of 70 GHz and f_max of 90 GHz were obtained     

选频~(14)CO_2-~(12)CO_2同位素激光器

我们研制了一台~(14)CO_2-~(12)CO_2同位素激光器,测量到激光谱线80条,其中40条是~(14)CO_200°1-(10°0,02°0)_I带的激光跃迁谱线,强线输出功率达4.0W以上;实验还观察到同位素的竞争效应,发现即使~(14)CO_2成份低于~(12)CO_2,其激光辐射仍占优势.     

Waveguide In0.53Ga0.47As-In0.52Al0.48As avalanche photodiode

A high-speed waveguide In_0.53Ga_0.47As-In_0.52Al_0.48 As separate absorption, charge, and multiplication avalanche photodiode suitable for operation at 1.55 μm has been demonstrated, a unity-gain bandwidth of 27 GHz was achieved with a gain-bandwidth product of 120 GHz     

Buried-Pt gate InP/In0.52Al0.48As/In0.7Ga0.3As pseudomorphic HEMTs

InP-based high electron mobility transistors (HEMTs) were fabricated by depositing Pt-based multilayer metallization on top of a 6-nm-thick InP etch stop layer and then applying a post-annealing process. The performances of the fabricated 55-nm-gate HEMTs before and after the post-annealing were characterized and were compared to investigate the effect of the penetration of Pt through the very thin InP etch stop layer. After annealing at 250 °C for 5 min, the extrinsic transconductance (G_m) was increased from 1.05 to 1.17 S/mm and Schottky barrier height was increased from 0.63 to 0.66 eV. The unity current gain cutoff frequency (f_T) was increased from 351 to 408 GHz, and the maximum oscillation frequency (f_max) was increased from 225 to 260 GHz. These performance improvements can be attributed to penetration of the Pt through the 6-nm thick InP layer, and making contact on the InAlAs layer. The STEM image of the annealed device clearly shows that the Pt atoms contacted the InAlAs layer after penetrating through the InP layer.     

Temporal stability of circulating current in thin film Tl2Ba2CaCu2O8 and YBa2Cu3O7

The temporal stability of trapped transport current in annular thin film Tl₂Ba₂CaCu₂O₈ (TBCCO) and YBa₂Cu₃O₇ (YBCO) wafers has been accurately measured and has been found to be of suitable quality for the stringent requirements of nuclear magnetic resonance (NMR) magnets. No detectable decay, to the limit of the experimental apparatus (2*10^-14 Ω), was detected in those wafers with transport current at or below the critical current density J_c. The critical current density, as previously determined from 12 μm meander lines, was confirmed in a wafer with a width of 1.9 cm. The profile of trapped magnetic field resulting from induced current was modeled in order to assess its effect on the uniformity of an NMR magnet