新的压电薄膜——Ta2O5

据报道,日本Yasuhiko Nakagawa和Yasuo Gomi用磁控反应直流二极管溅射法将Ta_2O_5,沉积在石英基片上,得到了单晶薄膜,并且首次观察到了这种薄膜的压电现象.用叉指换能器在Ta_2O_5薄膜上成功地激发了声表面波.在Ta_2O_5/熔石英基片上,当薄膜厚度h在hk(=2πh/λ)=1.0时,其机电耦合系数k~2=0.5％,它可与熔石英基片上ZnO薄膜的机电耦合系数相比拟. 利用Ta_2O_5单晶的X射线衍射数据,推断出Ta_2O_5     

One Step to Generate Cluster States Using Dipole-Induced Transparency in a Cavity-Waveguide System

We present a very simple scheme for generating four-qubit cluster states with one step using parity measurement based on dipole-induced transparency in a cavity-waveguide system. The scheme only uses the photon detectors to check the parity of the spatially separated dipole, which are the same （even parity） or different （odd parity） through measuring the light fields in the waveguide. The initial entangled states remain after nondetective identification and they can be used for successive tasks.     

An investigation on optical microfiber reflector with low reflectance

The backscattering characteristics of optical microfiber(OM) are experimentally studied by controlling heating temperature and cooling method during the OM fabrication process.OM samples with various reflectances from 0.1% to 1% are achieved.An OM with waist length of 5 mm,waist diameter of 1 μm,and approximately 0.5% reflectance is used as the end reflector of a fiber Fabry-Perol(F-P) interferometer.A piezoelectric ceramic transducer(PZT) fiber phase modulator is used to test the sensing performance of the fiber F-P interferometer.Experimental results verify that the OM with low reflectance can be used as a reflector in the F-P interferometer.     

《应用声学》2014年总目次 第33卷 第1-6期

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三角缺口正三角形纳米结构的共振模式

设计了一个三角缺口三角形破缺纳米结构,它是从正三角形底边切掉一个三角切片所构成.应用离散偶极子近似方法研究了其消光光谱及表面电场分布.结果发现,该破缺纳米结构的消光光谱中出现了具有Fano共振的线形.分析表明,这个Fano共振线形是由绑定与反绑定混合表面等离激元模式相互作用所致.研究了三角缺口三角形纳米结构的结构参数对Fano共振的影响.     

电大开孔箱体屏蔽效能分析解析模型

电磁脉冲武器能够通过"前、后门"耦合效应对箱体内部电子元器件及电路板造成损伤,从而对电气电子设备的安全性构成严重威胁,因此,开展箱体电磁屏蔽效能的分析研究具有重要意义.推导了任意入射波条件下电大开孔箱体屏蔽系数的解析解,并在此基础上对箱体屏蔽效能进行了分析研究.首先通过矢量分解,得出任意入射平面波的坐标分量;再基于Cohn模型,获得了电大开孔的等效电偶、磁偶极子;然后通过镜像原理,计算出总的赫兹电矢量位、磁矢量位;最终求得电大开孔箱体内部任意观测点的电场解析解,用于箱体屏蔽系数计算.设计了5组验证性实验,仿真结果表明:该解析算法相对CST的均方误差为11.565 d B,绝对误差为8.015 d B,相关系数为0.921,从而验证了该算法的准确性;解析算法仿真的平均耗时为0.183 s,仅占CST耗时的1/7530,从而验证了该算法的高效性.     

大气湍流对轨道角动量态复用系统通信性能的影响

通过数值仿真,以多个相位屏模拟大气湍流,研究大气湍流对轨道角动量(Orbital Angular Momentum,OAM)态复用通信系统质量的影响.改变大气湍流折射率结构常量C2n和传输距离z,分析其对OAM态复用系统归一化接收功率、误码率等的作用.研究结果表明当大气湍流强度增加和传输距离增长时,复用系统归一化接收功率下降、误码率增加.当C2n增大到5×10-13 m-2/3时,系统归一化接收功率下降到0.2以下,误码率增大到0.3以上;当传输距离增大到10 000m,系统归一化接收功率下降到0.3以下,误码率增大到0.35以上.同时,对比不同方位角指数l取值的两个OAM态复用系统受大气湍流的影响,发现:l取值越接近的系统,受大气湍流影响越大.在等同光学信噪比下大气湍流导致OAM态复用系统误码率性能降低2至3个数量级.该研究对OAM态复用系统的实用化具有积极的参考作用.     

相干偏振复用正交相移键控实时相干接收中的并行流水型恒模算法(英文)

在对相干偏振复用四相相移键控信号进行偏振解复用的实时相干接收机中,为高效补偿偏振效应,同时降低系统对时钟频率要求与系统中FPGA资源的使用量,对接收机中广泛采用的恒模算法从并行性、滤波器阶数、以及流水性3方面进行了研究改进,提出了并行流水型恒模算法.研究结果显示,在43Gb/s高速相干接收系统中,相干接收机的并行度宜为32,滤波器阶数宜为5.VPI与MATLAB联合仿真结果表明,采用本文提出的并行流水型恒模算法后,基于FPGA的四相相移键控信号实时相干接收机对时钟频率的要求可以降低到168MHz;在不丢包的情况下,系统能够处理43Gb/s相干接收系统中的全部数据,有效实现偏振解复用;在背靠背情况下,补偿1×10-3误码率的OSNR为14.5dB.利用高层次综合软件将并行流水型恒模算法下载到FPGA中,DSP资源的使用量仅仅是传统算法使用量的1/8.     

The application of laser reflective tomography in near-field measurements of ultrasonic transducers

With Laser Reflective Tomography（LRT）,the near fields of ultrasonic transducers were measured and analyzed.The principle of LRT measurement of ultrasonic field distribution was introduced and an experimental system was set up.Acoustic pressure of a multiple element piston transducer was measured by using of a laser vibrometer.Its distribution in amplitude and phase was obtained.The acoustic pressure in the same region was measured with a needle hydrophone to validate the LRT method.Furthermore,through reconstruction of acoustic fields,it indicated that LRT method is suitable for predicting the distribution on transducers＇surface and conditions of active elements.