Integrated optical electric field sensor based on a Bragg grating in lithium niobate

We demonstrate a new sensor concept for the measurement of oscillating electric fields that is based on Bragg gratings in LiNbO₃:Ti channel waveguides. This miniaturized sensor that works in a retroreflective scheme does not require metallic electrodes and can be directly immersed in an oscillating electric field. The electric field induces a shift of the Bragg wavelength of the reflection grating that is due to the electro-optic effect. The operating point of the sensor is chosen by adjusting the laser wavelength to the slope of the spectral reflectivity function of the grating. In this way the magnitude of an external electric field is measured precisely as the amplitude of modulated reflected light intensity by using a lock-in amplifier. The sensor principle is demonstrated by detecting low-frequency electric fields ranging from 50 V/cm to 5 kV/cm without any conducting parts of the sensor head. Furthermore, the ability of the sensor to determine the three-dimensional orientation of an external electric field by a single rotation along the waveguide direction is demonstrated. PACS 42.40.Eq; 42.82.-m; 42.82.Et     

光波导F-P干涉型电场和电压传感器

本文报道了 LiNbO₃质子交换光波导 F-P 干涉型电场和电压传感器的结构、制备、工作原理、实验装置与测量结果.用半导体激光器(780nm)作光源,测量了器件对频率在20Hz～1KHz 电场的响应特性,着重测量并得到工频(50Hz)交流电场(幅值为8.3～75V_zms/cm)和电压(20～180V_rms)与调制光输出电压之间的关系曲线.实验研究表明:该器件的线性度为1.4%,电场灵敏度为61.4mV_rms/V_rms/cm,电压灵敏度为25.6mV_rms/V_rms;且具有结构简单、制作容易、几何尺寸小、光传输插入损耗低等优点;稍加完善,可望制成实用化器件.     

First experimental observation of superscars in a pseudointegrable barrier billiard

With a perturbation body technique intensity distributions of the electric field strength in a flat microwave billiard with a barrier inside up to mode numbers as large as about 700 were measured. A method for the reconstruction of the amplitudes and phases of the electric field strength from those intensity distributions has been developed. Recently predicted superscars have been identified experimentally and--using the well-known analogy between the electric field strength and the quantum mechanical wave function in a two-dimensional microwave billiard--their properties determined.     

Experimental Investigation of Integrated Optical Intensive Impulse Electric Field Sensors

We design and fabricate an integrated optical electric field sensor with segmented electrode for intensive impulse electric field measurement. The integrated optical sensor is based on a Mach-Zehnder interferometer with segmented electrodes. The output/input character of the sensing system is analysed and measured. The maximal detectable electric field range （-75 kV/m to 245kV/m） is obtained by analysing the results. As a result, the integrated optics electric field sensing system is suitable for transient intensive electric field measurement investigation.     

Dependence of space charge field and gain coefficient on the applied electric field in photorefractive materials

Intensity dependent space charge field and gain coefficient in the photorefractive medium due to the two interfering beams have been calculated by solving the material rate equations in presence of externally applied dc electric field. The gain coefficient has been studied with respect to variations in the input intensity, modulation depth, concentration ratio and normalized diffusion field in the absence and presence of the externally applied dc electric field. Space charge field has also been computed by varying the intensity ratio in the presence and absence of the externally applied dc electric field. It has been found that the rate of change of the space charge field with the normalized dc field decreases with the increasing intensity ratio for different values of the normalized diffusion field. It has also been found that the externally applied dc electric field has appreciable effect only when it is larger than the diffusion field.     

高分辨紫外电子轰击互补金属氧化物半导体器件的实验研究

基于真空紫外光电阴极和背照式互补金属氧化物半导体(CMOS)图像传感器研制了紫外光响应的电子轰击CMOS(EBCMOS)器件,实现了EBCMOS器件在40 mlx光照度环境下的高分辨探测,电子图像灰度随电子能量的变化呈现出极好的线性关系.对器件成像分辨率测试的结果表明,在电场强度为5000 V/mm时,器件的空间分辨率可以达到25 lp/mm,与国际相关报道水平相当.研制的EBCMOS器件可直接在紫外弱光探测领域应用,如天文观察、高能物理、遥感测绘等,同时也可为下一步研制可见光和近红外敏感的EBCMOS器件提供参考.     

The contribution to the study of glassy As2Se3 in high electric fields

The dependence of the electrical conductivity on the intensity of applied electric field has been measured for temperatures in the range 330–430 K. The experimentally found exponential dependence in the high field limit has been interpreted in terms of thermionic field emission from localized states in the gap directly into the delocalized states in the band.     

球形光纤传输三维电场传感器

研制了一套用于小空间电磁脉冲测试的光纤传输电磁脉冲三维电场传感器。通过电磁仿真软件CST2011,研究了天线结构对被测场的影响,发现嵌入式探头与球形结构可以有效减小屏蔽壳体对电场扰动。讨论了传感器极间耦合及三维场合成误差,确定了主要设计参数。研制的三维传感器采用了屏蔽结构与偶极子天线的一体化设计,对外部电场屏蔽可达60 dB。在有界波电磁脉冲模拟器中的实验表明,传感器系统对于三维电场测量可达到设计要求,对被测电场扰动较小,极间耦合系数小于6%,三维场角度与峰值合成误差小于5%。传感器采用对称结构,满足自由空间场测量的需要。     

电场调制下单量子阱ZnCdSe／ZnSe的激射行为研究

近年来,随着宽禁带Ⅱ－Ⅵ族半导体激光器取得突破性进展［１］,对ＺｎＳｅ基超晶格与量子阱的受激发射也进行了广泛的研究［２,３］,同时对电场调制下的ＺｎＳｅ基超晶格的受激发射也有过报导［４］．但对于电场调制下的ＺｎＣｄＳｅ／ＺｎＳｅ基单量子阱的激射行为研...     

Characterization techniques for a MEMS electric-field sensor in vacuum

An accurate calibration of an electric-field sensor is difficult to carry out due to challenges involved in generating a uniform electric field over the sensor volume. Additionally, capacitive coupling between the field source and the sensors and related instrumentation tends to distort the measured field further. Sensor characterization includes not only calibration, but also determination of the frequency response (both magnitude and phase), noise power spectral density, dynamic range, and linearity. In this paper, we discuss characterization techniques for an unpackaged microelectromechanical systems (MEMS) electric field sensor in a vacuum chamber. The use of oppositely charged square plates at a spacing of half the plate width is advised by the IEEE 1308-1994 standard for generation of a uniform electric field. Previously, the U.S. Army Research Laboratory (ARL) has shown that by employing guard tubes in the construction of an electric field generating chamber, the fringing fields can be controlled, and the spacing between the endplates can be increased while maintaining a uniform field. A similar, smaller apparatus for generating a uniform axial electric field was constructed to fit into a vacuum bell jar. The considerations and techniques for minimizing error due to fringing and distortion from metal conductors will be presented, along with the techniques and laboratory equipment used for characterizing the sensor.     

Electro-optical transitions in a semiconductor cylindrical nanolayer

The single-electron states in a quantized cylindrical layer have been considered in the presence of a moderate homogeneous electric field, when the energy imparted to a charge carrier by the electric field becomes comparable to the energy of rotational motion of this particle. The corresponding energy spectrum and the envelopes of the wave functions of charge carriers in the layer have been obtained in an explicit form. The electro-optical absorption band of a weak electromagnetic wave has been calculated. It has been found that the absorption intensity increases with an increase in the intensity of the electric field. The external electric field leads to an explicit dependence of the absorption intensity on the effective masses of charge carriers. The absorption intensity decreases as the difference between the effective masses of charge carriers increases. There is also an effective broadening of the band gap, which is determined by the geometrical dimensions of the sample and the magnitude of the external field.     

基于原子的射频识别标签近场散射场矢量测量

基于原子的时间/频率、长度以及磁场、微波电场等方面的量子精密测量近年来引起广泛关注。里德堡原子作为微波精密测量工具,具有可溯源性好、空间分辨率高以及探测灵敏度高等优势。通过室温铯里德堡原子的电磁诱导透明光谱特征分析实现了微波电场矢量空间高分辨测量。利用铯原子蒸气池中共线的耦合光和探测光形成了6S_1/2-6P_3/2-51D_5/2的阶梯型三能级系统,5.365 GHz微波电场将诱导相邻里德堡态51D_5/2-52P_3/2的共振跃迁,导致阶梯型三能级系统的电磁诱导透明光谱发生Autler-Townes分裂。通过计算光谱的分裂间隔可得到可溯源至普朗克常数的微波电场强度,微波电场测量的空间分辨率达到1/31被测微波波长。特别是提出一种新的微波电场极化方向测量方法,解决了基于里德堡原子进行微波电场极化方向测量时无法分辨互补角的问题。通过对射频识别标签的近场散射场进行矢量测量,实现了标签角度的有效识别,角度分辨率达到1.64°,测量结果与有限元分析方法仿真结果吻合地很好。该研究对于微波电场空间高分辨成像、射频识别标签的设计和识别以及电磁兼容测试等方面具有重要价值。     

高压多脉冲真空间隙击穿实验研究

 在真空间隙击穿机理的理论基础上,设计了高压多脉冲下真空间隙的击穿实验方案,对相同材料的多对电极间隙在高压单脉冲和三脉冲下的真空击穿特性进行了实验研究。实验结果与脉冲下真空间隙的击穿机理相符,对脉冲数量增加对真空间隙宏观击穿场强的影响进行了验证,推断出了决定真空间隙宏观击穿场强的关键因素,并对多脉冲加速间隙最大宏观场强的设计提出了建议。     

Near-field acoustic intensity measurements using an accelerometer-based underwater intensity vector sensor

An accelerometer-based underwater acoustic intensity vector sensor is used to measure the acoustic nearfield of a single spherical source, and a pair of sources that vibrate in or out of phase with each other. The intensity sensor consists of co-located pressure and inertial sensors within a neutrally buoyant probe body. The design of this probe has been published previously. The measurements were performed in a large tank at a frequency of 5 kHz for two sources of different sizes, corresponding to ka values of 0.7 and 1.2 respectively, where k is acoustic wavenumber and a is the source radius. By way of validation, the acoustic intensity field from two closely spaced, interacting spherical radiators is predicted using the exact theory of the translational addition theorem for spherical wave functions. The predictions using this theory compare favorably well with the measured intensity field. Beam pattern and calibration data obtained for the intensity sensor suggest that underwater acoustic intensity generated by simple and complex sources can be measured to an accuracy of ±1 dB provided that ka is less than approximately 0.2.     

激光诱导光学材料后表面损伤的数值模拟

 采用3维时域有限差分方法和完全匹配吸收层,模拟了长方体缺陷在熔石英前后表面时对入射激光为TM波的调制作用,绘出了截面上的电场强度分布及最大电场强度随熔石英深度变化的曲线,并进行了比较和分析。结果表明：缺陷在前表面上时,后表面附近的最大电场强度2.522 41 V/m大于缺陷附近的1958 83 V/m;缺陷在后表面上时,材料中的最大电场强度为2.799 38 V/m,且出现在后表面附近。无论该缺陷在前表面还是在后表面,最大电场强度都是出现在后表面附近,表明光学材料的后表面在一定程度上更容易被损伤。     

Finite Element Analysis of Piezoelectric Polymer-Coated D-Fiber Intended for Electric Field Sensing

We report, for the first time, the advantage of using a polymer-coated D-fiber over conventional circular fiber as the sensing element in an all-fiber electric field sensor. Finite element analysis has been used to studythe strains in a D-fiber subjected to an external electric field. The optical D-fiber carrying a transversely poled piezoelectric poly(vinylidene fluoride) polymer coating was modeled by using three-dimensional stress analysis. The response of the D-fiber electric field sensor was determined over a wide frequency range from 100 Hz to 50 MHz. The modeling predicts that the resulting strains will cause a phase shift of 0.06 rad V m in the low-frequency (axially unconstrained) region and 0.002 rad V m in the high-frequency (axially constrained)region. An increase in the phase modulation sensitivity by a factor of 3 compared to conventional circular fiber has been achieved by utilizing the unique properties of the D-fiber structure.     

Cold emission of negative ions from porous graphite

The electric field strength in the near-wall layers of thermonuclear facilities can be sufficient for the emission of negative ions from the surface of plasma facing materials. The mass spectra of negative ions from MPG-8 porous graphite at electric field strengths up to 4 × 10⁶ V/m and the surface composition of the target have been studied by ion scattering spectroscopy. The dependence of the mass composition of negative ion emission and residual gas on the sample’s temperature has been measured and a correlation between the intensity of negative hydrogen-ion emission and the desorption of water has been established. The temperature dependence of the emission of negative ions and clusters of carbon and hydrocarbon is in qualitative agreement with the chemical erosion of graphite.     

Electric-field effect on positronium formation and decay in some polymers and fused quartz

The effect of static electric field on the formation and annihilation of positronium in polyethylene, polystyrene, teflon, quartz, nylon and perspex has been investigated employing a fast timing spectrometer with prompt resolution (fwhm) ∼200 ps at the positron experimental settings. No significant variation in the lifetime of the long lived pick-off component with electric field has been observed. The intensity of the long-lived pick-off component decreases with increase of the field in all the cases investigated except in nylon and perspex where the intensity remains constant with the field. The results have been discussed in the frame work of the spur reaction model proposed by Mogensen and also in the light of the Ore gap model, as discussed by Brandt and Wilkenfeld. Another interesting correlation seems to exist between positronium formation and dielectric loss factor; in case of increasing loss factor there is a decrease in the effect of electric field. Work performed at Saha Institute of Nuclear Physics, Calcutta 700009, India.     

All-Optical Photorefractive Effect in Carbazole-Based Azo-Side Group Polymer

We observe the photorefractivity without bias voltage or prepoling in a bifunctional photorefractive polymer. The maximum two-beam coupling gain is measured to be 126cm^-1 at zero bias voltage. The sample is considered to be poled by the photoinduced longitudinal electric field, which is formed due to the light intensity gradient along the light path. The expression of the electric field was deduced. The energy transfer direction between two writing beams and light intensity dependence of the two-beam coupling gain coefficient is predicted to be consistent with the experimental results. Furthermore, the dependence of the two-beam coupling gain coefficient on external applied electrical field is measured and this experiment verifies the existence of the photoinduced longitudinal electric field.     

脉冲电场测试中的激光供电技术

为解决脉冲电场测试系统中的供电问题，设计了一套激光光纤供电系统，该系统由激光器、多模光纤及光电池构成。重点研究了激光器与光纤的耦合问题，设计了透镜系统对激光器输出光束进行准直和压缩。通过MOCVD法研制了GaAs光电池，并制作了椭球形"光伏眼"来提高光电转换效率。仿真和实验表明:采用透镜耦合时，激光器与光纤的耦合效率可达80%以上，远远高于直接耦合时的16%，改进后的"光伏眼"耦合效率相比直接耦合时提高了54.5%，激光供电系统的转化效率在40%以上。该系统的研制为解决脉冲电场的供电问题提供了一种方案。