量子密码术中的即插即用系统

讨论了利用法拉第镜补偿光在光纤中传输的偏振波动,介绍了量子密码术中基于法拉第镜的即插即用系统,并对即插即用系统进行简单相位编码分析。在系统中干涉脉冲遵循确切相同的路径,确保非常高的稳定性和自我补偿,使用法拉第镜自动补偿光纤中的任何双折射效应和偏振相关损耗。     

利用法拉第筒测试环形强流电子束束流

通过优化设计法拉第筒的响应电阻和分布电感,在“TPG700”平台上对无箔二极管阴极发射的环形电子束束流进行轴向测试。结果表明,无波二极管工作在低磁场(<1 T)条件下,在二极管电压较低时,优化后的法拉第筒测试获得的电子束束流前沿较慢,随着二极管电压的升高,电子束束流前沿明显变快;在强磁场(>2 T)条件下,法拉第筒测试结果与罗果夫斯基线圈测试结果一致。该结果表明,相比于罗果夫斯基线圈,法拉第筒更能准确地测试出无箔二极管的前向电子束束流。     

Coherence Multiplexing System Based on Asymmetric Mach–Zehnder Interferometers for Faraday Sensors

An optical coherence multiplexing system for Faraday sensors is proposed. With an asymmetric Mach-Zehnder (M-Z) interferometer, the linearly polarized light from a Faraday sensor is decomposed into two orthogonal modes, which are interrogated by a path-scanning Michelson interferometer at different path positions. The variations in the intensities of these two modes are utilized to deduce the rotation of the polarization plane, which is related to the measurand tested by the Faraday sensor. By employing multiple asymmetric M-Z interferometers with arm-lengths carefully controlled, the sensing signals of the multiplexed Faraday sensors are obtained and well separated in one scan of the Michelson interferometer.     

电离层Faraday效应对远程预警雷达性能的影响

在对近地空间目标进行预警跟踪时,雷达发射的电磁波会在电离层中传播,电离层作为磁化等离子体,会导致电磁波产生Faraday旋转,从而对雷达探测性能造成影响。通过数值计算的方式,仿真了Faraday旋转效应导致的雷达极化失配损耗,并对仿真结果进行了分析。通过仿真结果可以看出:太阳活动高年,Faraday旋转角比太阳活动低年大;雷达工作频率越高,受Faraday旋转影响越小;目标仰角较低时,线极化失配损耗较小;椭圆极化方式下,极化失配损耗随椭圆轴比增大而增大;用圆极化方式可以最大程度地减小由Faraday旋转导致的雷达探测性能降低。     

Determination of the ionospheric electron content utilizing satellite signals

Various methods for the determination of the ionospheric electron content are possible when satellite-borne signals can be used. The paper compares the results from Doppler shift, Faraday rotation, Doppler data combined with Faraday rotation data, and topside and bottomside soundings. The often neglected prerequisite for the application of Doppler and Faraday methods is radio propagation along the same ionospheric path for the different frequencies involved. Criteria for correct application are discussed. The comparison of inflection time moments is chosen for data selection. The usage of the Doppler slopes at the time of simultaneous inflection provides reliable data of the electron content. The diurnal variation is given. The Faraday rotation rate measurement has been made a continuous one by special equipment of G. Vogt. The simultaneous use of two Doppler slopes at different frequencies and of the Faraday rotation rate at one of these frequencies results in the measurement of the effective component of the geomagnetic field. Thus, a method free from any assumptions is on hand for the electron content. From the radio-frequency sounding of the topside-sounder satellites and from simultaneous bottomside soundings a complete ionospheric profile is obtained, the integration of which results in data for the total content. A comparison of the results of the different methods is permitted within the limitations brought about by the various theoretical and experimental assumptions made.     

On the detection of Faraday rotation in linearly polarized L-band SAR backscatter signatures

The potentially measurable effects of Faraday rotation on linearly polarized backscatter measurements from space are addressed. Single-polarized, dual-polarized, and quad-polarized backscatter measurements subject to Faraday rotation are first modeled. Then, the impacts are assessed using L-band polarimetric synthetic aperture radar (SAR) data. Due to Faraday rotation, the received signal will include other polarization characteristics of the surface, which may be detectable under certain conditions. Model results are used to suggest data characteristics that will reveal the presence of Faraday rotation in a given single-polarized, dual-polarized, or quad-polarized L-band SAR dataset, provided the user can identify scatterers within the scene whose general behavior is known or can compare the data to another, similar dataset with zero Faraday rotation. The data characteristics found to be most sensitive to a small amount of Faraday rotation (i.e., a one-way rotation <20/spl deg/) are the cross-pol backscatter [/spl sigma//spl deg/(HV)] and the like-to-cross-pol correlation [e.g., /spl rho/(HHHV/sup */)]. For a diverse, but representative, set of natural terrain, the level of distortion across a range of backscatter measures is shown to be acceptable (i.e., minimal) for one-way Faraday rotations of less than 5/spl deg/, and 3/spl deg/ if the radiometric uncertainty in the HV backscatter is specified to be less than 0.5 dB.     

穿越电离层双程传播-法拉第旋转的理论分析

对于双程传播,考虑目标的散射系数,利用多波模合成概念,导出了包含法拉第旋转角(Ω)的波场的表达式.波场仍分为两部分,一部分,因法拉第旋转角相互抵消,而不受影响,即寻常波.另一部分,波的相位以2Ω为参数,波的的振幅以4Ω为参数,而受到法拉第旋转的影响,即非常波.当工作频率低于1000 MHz时,法拉第旋转的影响,是严重的.一般说来,双程法拉第旋转角并非小量级,而且是以简谐函数出现,难于总结简明规律.如果,散射系数随入射波偏振的不同而改变,那么,两部分波所受到的影响将更为复杂,如结论所示.     

用IGS发布的TEC数据提高法拉第旋转校正精度

电磁波穿过电离层时引入的法拉第旋转是导致全极化微波辐射计观测亮温产生交叉极化的重要原因.分析得知IRI（international reference ionosphere）模型产生的TEC（total electron content）数据在部分低纬地区无法满足全极化辐射计对法拉第旋转的校正精度要求.为提高校正精度,分析了沿观测路径积分法和应用IGS（International GPS Service）发布的TEC数据校正两种方法对校正精度的影响.结果表明,沿观测路径积分法不能有效改善校正精度,而应用IGS数据校正可大幅提高低纬地区法拉第旋转校正精度,满足全极化微波辐射计对极化旋转角的校正精度要求.     

Magnetooptic mode splitting in an anisotropic laser cavity

The normal modes of an anisotropic laser resonator containing an intracavity Faraday rotator have been investigated. Below a threshold value of rotation, the Faraday cell rotates the electric field vector of the linearly polarized modes. Above this value, each axial mode splits into two elliptically polarized waves. The frequency difference of these modes is then dependent on the Faraday rotation angle. Experimental results obtained using a 3.39-μ He-Ne laser with two Brewster windows and a YIG intracavity Faraday cell are in agreement with the results calculated from a normal mode analysis.     

四频差动激光陀螺法拉第片最佳入射角的研究

为了探究入射光偏振态对四频差动激光陀螺法拉第片最佳入射角的影响,建立四频差动激光陀螺法拉第片三光束干涉的琼斯矩阵,利用计算机进行数值计算,模拟圆偏振光和椭圆偏振光在陀螺仪内的传播方程,并通过搜索不同入射角情况下-40℃~80℃温度范围内磁圆二向色性差分损耗的振幅最小值来选取最佳入射角。结果表明,圆偏振模式下和椭圆偏振模式下法拉第片的最佳入射角有一定差别,这种差别足以影响到激光陀螺仪的测量精度,因此在安装法拉第片时应考虑入射光偏振态对其最佳入射角的影响;此外,法拉第片的最佳入射角与入射光s分量(垂直于入射面)、p分量(平行于入射面)在反射镜上的反射相位差以及反射镜的反射系数均有关。     

Faraday效应对空间目标探测雷达的影响

分析了电离层Faraday旋转效应对空间目标探测雷达的影响。从磁离子理论出发,结合电离层模型和地球磁场模型,使用了一种快速的Faraday旋转角计算模型,并与传统使用的经验计算方法进行了比较,表明该方法普适性强,更适用于中国地区。针对当前国际上典型的空间目标探测雷达工作频段,选取我国海口（低纬地区）和长春（中纬地区）为代表,分别计算了太阳活动极大年和极小年间的Faraday旋转角,给出了仿真结果并进行分析,表明Faraday旋转效应给线极化方式雷达带来明显的回波能量损失。在进行雷达设计时,需要将该效应与雷达系统性能综合考虑,采用合适的天线极化方式。     

A Faraday cage isolation structure for substrate crosstalksuppression

We have exploited a recently-developed, through-wafer via technology in silicon to implement a novel Faraday cage scheme for substrate crosstalk suppression in system-on-chip (SOC) applications. The Faraday cage structure consists of a ring of grounded vias encircling sensitive or noisy portions of a chip. The via technology features high aspect ratio, through-wafer holes filled with electroplated Cu and lined with a silicon nitride barrier layer. The new Faraday cage structure has shown crosstalk suppression of 40 dB at 1 GHz and 36 dB at 5 GHz at a distance of 100 μm. This is about 10 dB better than any other isolation technique previously reported     

Microwave Faraday Effect and Propagation in a Circular Solid-State Plasma Waveguide

The microwave Faraday effect in a solid-state plasma waveguide under a relatively high magnetic field (/spl mu//sub e/B/sub 0/>>1) is investigated. Field configurations in the solid-state plasma waveguide are first analyzed. It is shown that two types of nondegenerate circularly polarized quasi-TE waves exist in the waveguide. The propagation constants of the quasi-TE waves are obtained by means of a variational method. The microwave Faraday effect in the solid-state plasma waveguide is formulated. It is shown that geometrical factors and reflections from the waveguide discontinuities have significant influences on the Faraday effect. Experimental results of the Faraday effect at 36 GHz through a soIid-state plasma waveguide are reported. In the experiment n-type indium antimonide crystals are used. The comparison of the experimental data with the theory shows good agreement.     

Calibration of linearly polarized polarimetric SAR data subject to Faraday rotation

A model for linearly polarized fully polarimetric backscatter measurements is used, incorporating the effects of system noise, channel amplitude, phase imbalance, crosstalk, and Faraday rotation. A step-by-step procedure is outlined for correction (or calibration) of fully polarimetric data subject to Faraday rotation, to recover the true scattering matrix. The procedure identifies steps for crosstalk removal and correction of channel imbalances that are robust in the presence of Faraday rotation. The final steps in the procedure involve a novel strategy for estimation and correction of Faraday rotation. Three approaches to estimate the (one-way) Faraday rotation angle /spl Omega/ directly from linear (quad-) polarized synthetic aperture radar (SAR) backscatter data obtained by a spaceborne SAR system are described. Each approach can initially be applied to the signature of any scatterer within the scene. Sensitivity analyses are presented that show that at least one of the measures can be used to estimate /spl Omega/ to within /spl plusmn/3/spl deg/ to 5/spl deg/, with reasonable levels of residual crosstalk, noise floor, channel amplitude, and phase imbalance. Ambiguities may be present in the estimates of /spl Omega/ of /spl plusmn/n/spl pi//2 - the impact of this is discussed, and several approaches are suggested to deal with this possibility. The approach described in this paper is relevant for future L-band spaceborne SARs and removes one key obstacle to the deployment of even longer wavelength SARs (e.g., an ultrahigh frequency or P-band SAR) in Earth orbit.     

Faraday chiral media revisited. I. Fields and sources

Faraday chiral media, previously conceptualized as chiroplasmas or chiroferrites, are envisioned to combine the effects of Faraday rotation and chirality. Electromagnetic field representations for arbitrary sources are derived after the previous correct characterization of the constitutive relations of such media. The scalar Hertz potential (SHP) technique is employed and its applicability is thoroughly investigated. In particular, it is shown that all field components can be derived from one scalar Green function (plus so-called auxiliary source potentials) in source problems, whereas one scalar superpotential suffices for source-free problems. Expressions pertaining to radiation from electric and magnetic dipole sources are presented in a simple and compact form. Further generalizations of the results and the actual realizability of Faraday chiral media are discussed     

A new Faraday rotator using a thick Gd:YIG film grown by liquid-phase epitaxy and its applications to an optical isolator and optical switch

A new Faraday rotator using a thick garnet film grown by liquid-phase epitaxy (LPE) has been proposed and film growth technology for the rotator has been investigated. The new Faraday rotator had good features of very low cost and small size, due to high productivity of the LPE-grown film and low magnetic saturation field, respectively. By using the new Faraday rotator, an optical isolator and magnetooptic switch for single-mode fiber systems have been developed. The optical isolator featured 0.8-dB insertion loss and 25-dB isolation at 1.3-μm wavelength. The magneto-optic 1 × 2 switch was independent of light polarization and featured 1.3-1.7-dB insertion loss, -25-dB crosstalk, and 30-μs switching time at 1.3-μm wavelength. Minimum switching voltage was ±5 V. Magneto-optic devices using the new Faraday rotator is practical for use in1.2-1.7-mum wavelength fiber-optic systems, because of good optical properties, compactness, and low cost.     

Impedance matching considerations for ferrite Faraday rotators

When a linearly polarized plane wave propagates from a dielectric medium into a medium with Faraday rotation, a reflected wave will always occur at the interface. This reflection is necessary because the normal-mode wave impedances in the medium with Faraday rotation are nondegenerate, while the equivalent normal-mode wave impedances for the dielectric medium are degenerate. Therefore it is not possible to match both normal modes simultaneously at the interface. This paper investigates the peculiar reflected wave associated with impedance matching of Faraday rotators, and shows that it should have minimal impact on practical devices.     

Helical antenna for satellite transmission†

The use of helical antennas for satellite transmission is proposed. The polar diagram, directivity and polarization characteristics are outlined. The advantages of circularly and elliptically polarized waves transmitted from the helical antenna for Faraday rotation experiments are discussed. The use of helical array is comparatively more compact, radiation characteristics are frequency independent and the polarization of the radiated wave is more stable. These features enable an accurate measurement of the Faraday rotation which is likely to yield a better estimate of total electron content.     

磁致线双折射对法拉第旋转器消光比的影响

本文从磁光材料的介电张量出发,分析了磁致线双折射与法拉第旋转器消光比的关系,并给出了实验验证。结果表明,磁致线双折射是影响法拉第旋转器消光比的主要因素。