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测量设备无关量子密钥分配方案可以移除所有的探测器侧信道漏洞,通过结合诱骗态方案可以生成无条件安全的密钥.本文研究了非对称信道传输效率下三强度诱骗态测量设备无关量子密钥分配系统的密钥生成率与信道传输损耗的关系,比较了对称信道传输效率和非对称信道传输效率下的距离比率对单边传输效率、单光子误码率和量子密钥生成率的影响,仿真结果表明随着信道不匹配度逐渐增加,可容忍信道传输损耗由对称信道情形下的62 dB分别降至38 dB(距离比率为0.5)和17 dB(距离比率为0.1),能够安全提取密钥的可容忍传输损耗下降较快,密钥生成率的安全传输距离也随之降低.实验中可以采取调节信号光强度的方式提高非对称传输效率下测量设备无关量子密钥分配系统的密钥生成率,为实用的量子密钥分配实验提供了重要的理论参数. 相似文献
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研制出一种新型抗弯曲大模场面积石英光子晶体光纤. 利用光子晶体光纤结构设计的灵活性, 通过规划缺陷的位置及空气孔的尺寸, 实现了大模场面积单模及低弯曲损耗特性.应用建立的实际光子晶体光纤特性分析模型, 研究了研制光纤的模式特性和弯曲特性, 在波长1064 nm处, 平直状态下光纤的模场面积可以达到2812 μm2, 基模限制损耗为0.00024 dB/m, 高阶模限制损耗高于1.248 dB/m. 基模和高阶模之间的高传输损耗差, 保证了在获得大模场面积的同时实现单模传输. 弯曲半径和弯曲方向角所带来弯曲损耗变化的研究结果显示, 即使在弯曲半径小到5 cm时, 弯曲损耗也在10-3 dB/m量级以下, 而且在弯曲半径为30 cm时光纤可承受的弯曲方向角范围扩展至-60°–60°. 研制的光纤具有良好的低弯曲损耗特性, 可有效解决非对称结构所带来的光纤弯曲特性对弯曲方向角敏感的问题. 该光纤在高功率光纤激光器、放大器及高功率传输等技术领域具有重要的应用价值.
关键词:
光子晶体光纤
大模场面积
低弯曲损耗
弯曲方向角 相似文献
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金属纳米结构的表面等离激元可以突破光学衍射极限,为光子器件的微型化和集成光学芯片的实现奠定基础.基于表面等离激元的各种基本光学元件已经研制出来.然而,由于金属结构的固有欧姆损耗以及向衬底的辐射损耗等,表面等离激元的传输能量损耗较大,极大地制约了其在纳米光子器件和回路中的应用.研究能量损耗的影响因素以及如何有效降低能量损耗对未来光子器件的实际应用具有重要意义.本文从纳米线表面等离激元的基本模式出发,介绍了它在不同条件下的场分布和传输特性,在此基础上着重讨论纳米线表面等离激元传输损耗的影响因素和测量方法以及目前常用的降低传输损耗的思路.最后给出总结以及如何进一步降低能量损耗方法的展望.表面等离激元能量损耗的相关研究对于纳米光子器件的设计和集成光子回路的构建有着重要作用. 相似文献
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通过理论和数值模拟方法,考虑金属粗糙度的情况下,研究了加工垂直度公差角在0~6范围内变化时折叠波导慢波结构的工作性能,结果表明:金属波导表面的粗糙度增大时,慢波结构中电磁信号的传输损耗增大;垂直度公差角的增大也使得电磁信号的传输损耗增加,而且垂直度公差角所引起的结构变化会引起器件的电压工作点漂移、带宽降低等。 相似文献
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本文研究了Bi-2223高温超导带材的交流传输损耗和频率及运行电流的关系, 调查了热循环过程对交流传输损耗的影响. 实验中, 使用了Lock-in 放大器, 利用四引线法来测量带材交流传输损耗. 实验在温度为77K频率从45Hz到135Hz下进行. 在调查损耗和频率及运行电流的关系时, 发现在运行电流幅值小于临界电流时, 每周传输损耗和频率无关, 说明这时的损耗主要来源于磁滞损耗, 实验结果和Norris椭圆模型的计算结果很接近. 在研究交流传输损耗和热循环的关系时, 发现随着冷热循环次数的增加, 交流损耗也在增加. 这种损耗的增加来源于冷热循环过程中产生的应力, 这种应力的释放减弱了晶粒间的Josephson连接, 使临界电流下降, 从而造成了交流传输损耗的增加. 相似文献
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优化了一种基于表面等离激元银纳米链的马赫-曾德干涉式传感结构.该结构由参考臂、传感臂及纳米线波导构成.纳米线波导由银纳米线包裹一定厚度的硅来构成.引入两条银纳米链分别作为马赫-曾德干涉仪的参考臂和传感臂,并研究所设计结构的传输特性,通过降低传输损耗以提高所设计结构的精确度与灵敏度.相比于两条完全相同的银纳米线作为参考臂和传感臂的情况,在参考臂和传感臂改为银纳米链后,传输特性有明显提高,单位长度损耗明显降低.这是由于银纳米链中的单元结构之间的长程/库仑相互作用增强了结构中的电磁场,进而降低了传输损耗.将两条银纳米链的晶格常数设置为不同的情况,研究发现,在特定的银包硅纳米线的宽度与某些占空比下,含有非对称的银纳米链结构的单位传输损耗小于含有对称的银纳米链结构.由此可以知道,具有小损耗的银纳米颗粒链可以弥补大损耗的银纳米颗粒链的传输损失.利用这个特点,进一步优化设计结构,将一侧银纳米链改为纳米线.改变另一侧银纳米链的晶格常数与占空比,可以发现大多数情况下,这类结构传输特性优于含有两条银纳米链以及含有两条银纳米线的结构.本文的设计结构可以大幅减小传统的马赫-曾德干涉仪的传输损耗,且在结构的制备... 相似文献
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Experimental verification of effect of horizontal inhomogeneity of evaporation duct on electromagnetic wave propagation 下载免费PDF全文
《中国物理 B》2015,(4)
The evaporation duct which forms above the ocean surface has a significant influence on electromagnetic wave propagation above 2 GHz over the ocean. The effects of horizontal inhomogeneity of evaporation duct on electromagnetic wave propagation are investigated, both in numerical simulation and experimental observation methods, in this paper. Firstly, the features of the horizontal inhomogeneity of the evaporation duct are discussed. Then, two typical inhomogeneous cases are simulated and compared with the homogeneous case. The result shows that path loss is significantly higher than that in the homogeneous case when the evaporation duct height(EDH) at the receiver is lower than that at the transmitter. It is also concluded that the horizontal inhomogeneity of the evaporation duct has a significant influence when the EDH is low or when the electromagnetic wave frequency is lower than 13 GHz. Finally, experimental data collected on a 149-km long propagation path in the South China Sea in 2013 are used to verify the conclusion. The experimental results are consistent with the simulation results. The horizontal inhomogeneity of evaporation duct should be considered when modeling electromagnetic wave propagation over the ocean. 相似文献
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Dielectric losses in the patient may impair radiofrequency receiver coil sensitivity, and transmitter coil efficiency, in nuclear magnetic resonance (NMR) imagers. The frequency dependence of this loss mechanism is derived. Patient losses in a solenoidal head coil used for imaging heads were simulated by a cylindrical saline phantom. The frequency dependence of the loss introduced by the phantom can indicate whether dielectric losses in the patient will be significant compared to eddy current losses. The detuning caused by the phantom is used to calculate an upper limit for the distributed stray capacitance between coil and patient. Given the approximate conductivity of the patient, an upper limit for the dielectric loss can be estimated. Some methods of reducing patient dielectric losses are suggested. 相似文献
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M. Reza Hedayati Rad F.D. Kashani M.M. Eftekhari M. Reza Mahzoun 《Optics & Laser Technology》2010,42(8):1269-1275
The propagation properties of Gaussian laser beams through a complete optical path including free space and the optics of transmitter and receiver containing a collimator, an aperture and a lens is studied. Based on the Collins integral and using the second order moment method, analytical formulas for intensity distribution and Power In Bucket (PIB) along the propagation path are derived. The effects of initial beam divergence, collimator–source separation distance and beam width deviation on laser beams properties are investigated. Obtained results are confirmed and illustrated with numerical examples and resulted graphs. 相似文献
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A large, flat ultrasonic transmitter and a small receiver are developed for studies of material properties in acoustic transmission goniometry. While the character of the wave field produced by the transmitter can be considered as a plane wave as observed by the receiver, diffraction effects are noticeable near critical angles and result in the appearance of weak but detectable arrivals. Transmitted ultrasonic waveforms are acquired in one elastic silicate glass and two visco-elastic acrylic glass sample plates as a function of the angle of incidence. Phase velocities are determined from modeling of the shape of curves of the observed arrival times versus angle of incidence. The waveform observations are modeled using a phase propagation technique that incorporates full wave behavior including attenuation. Subtle diffraction effects are captured in addition to the main bounded pulse propagation. The full propagation modeling allows for various arrivals to be unambiguously interpreted. The results of the plane wave solution are close to the full wave propagation modeling without any corrections to the observed wave field. This is an advantage as it places confidence that later analyses can use simpler plane wave solutions without the need for additional diffraction corrections. A further advantage is that the uniform bounded acoustic pulse allows for the detection of weak arrivals such as a low energy edge diffraction observed in our experiments. 相似文献
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Statistical characteristics of a wave propagating through a layer with random irregularities are investigated by a simulation procedure. The investigation is carried out within the geometrical optics approximation in its validity range. It is shown that when the irregular layer is a long distance from the source and observer, a significant role in the formation of eikonal (phase path) fluctuations is then played by trajectory fluctuations in regions of the propagation medium, free from irregularities before and after the irregular layer. With these variations taken into account, which are neglected in conventional perturbation theory, we obtained approximate expressions for the dispersion and the correlation function of the eikonal. We investigate the behaviour of the eikonal dispersions, the angles and correlation functions of the eikonal and field for different disturbances of the medium, and for different distances of the receiver and transmitter from the layer boundaries. 相似文献
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基于长基线透射式能见度仪分析了影响透射仪收发两端探测光路准直的因素。从透射仪的测量原理出发,阐述了探测光路准直通过影响接收端接收光强进而影响透射仪探测精度的机制。仿真研究了透射仪收发两端探测光路准直出现偏差对接收端接收光强的影响。研究结果表明,在一定大气能见度条件下,透射仪的测量误差与接收端接收光强的测量误差成线性关系。透射仪收发两端的对准状态对透射仪接收端接收光强具有重要影响,发射端姿态角每变化0.01,接收端接收光功率变化0.02 mW,发射端姿态角变化会明显降低透射仪接收端接收光强,增大接收端接收光强的测量误差,对能见度的测量精度影响较大。 相似文献
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Wang L Lavrentyev AI Rokhlin SI 《The Journal of the Acoustical Society of America》2003,113(3):1551-1559
The accuracy of a plane wave approximation for phase velocity measurements in isotropic and anisotropic material using the angle-beam-through-transmission method has been investigated numerically and experimentally. In this method the velocity is measured in different propagation directions as a function of incidence angle. The effect of two factors on the measurement accuracy have been discussed: intrinsic phase shift of the transmitted signal through a fluid-solid interface and beam diffraction due to the finite beam size of receiver and transmitter. It is shown that the interface-induced phase shift can introduce an error in time delay measurements of the shear wave after the first critical angle and that this time delay error can be accurately corrected for. Numerical results obtained by a time-domain beam model show that except at the critical angles, the finite width of the transmitter and receiver only affects the amplitudes of the transmitted signals and has almost no effect on the measured zero-cross time delay; therefore the plane wave approximation for obtaining phase velocity from the measured time delay data by this method and the plane wave interface-induced phase correction are fully applicable. 相似文献
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The multiple-path sound propagation in deep water is conducive to source localization of an underwater target.The transmission losses(TLs) and broadband pulse multiple-path propagation characteristics from a deep receiver is analyzed by using the experimental data from deep water area in the South China Sea(SCS).The results indicate that the width of the direct zone near the bottom of 4300 m water depth is about 30 km.The TLs in the direct zone near the bottom are much less than those in the shadow zone.It is meaningful for underwater sound source detection.Moreover,the time delay between the direct path and the bottomsurface-reflected path for a receiver near the bottom decreases monotonically with the source range.According to the linear relationship between the time delay of multipath and source range,a source localization method is presented to estimate the range of underwater target.The experimental results show that the estimated ranges are consistent with the global position system(GPS) measurements,and the mean square error of the estimation results is less than 0.28 km. 相似文献
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Yazan A. Alqudah 《Optics Communications》2012,285(6):1053-1061
The study of indoor optical wireless (OW) environment is complicated by the difficulty of obtaining accurate impulse response for a large number of transmitter/receiver locations. An accurate impulse response for a given receiver location requires not only direct path, but also reflections up to nth order. The impulse response obtained is only valid for a specific location and for specific receiver parameters. If a receiver moves, the impulse response has to be recalculated. In this paper, we utilize an efficient approach for calculating optical wireless channel to study the optimal region of transmitters and receivers in a multi spot diffusing configuration. This paper takes advantage of an efficient calculation technique to study the optimal layout of receiver locations and transmitter locations in multi spot diffusing environment. Received power and delay spread are used as metrics to optimize receiver and transmitter layouts. 相似文献