基于激光偏振调制的全光Cs原子磁力仪研究

采取对激光左旋+偏振态和右旋-偏振态周期性调制产生共振的方法,实现对Cs原子拉莫尔进动频率的检测,取代了采用射频线圈产生共振的方法而实现了对磁场的全光检测,从而避免了传统光泵原子磁力仪信号串扰的问题。展示了该方法对原子磁矩在磁场中进动频率的检测原理,分析了该模式下的信号特征,根据信号特征设计了对拉莫尔进动信号的检测和处理系统。同相信号显示为洛伦兹线形;正交信号显示为色散线形,在共振频率处大小为0;相位信号显示为连续单调递减函数,在共振频率处大小为0。正交信号和相位信号均可以用来锁定共振频率点,实现磁场测量。     

利用高灵敏的无自旋交换弛豫原子磁力仪实现脑磁测量

设计了基于无自旋交换弛豫(SERF)的高灵敏度非低温铷原子磁力仪,其灵敏度在15 Hz处达到了6fT/(Hz)~(1/2)。利用此SERF磁力仪,在屏蔽筒内测量了人脑视觉皮层在睁眼和闭眼状态下的磁场差异。该SERF磁力仪采用抽运-探测双光模式,与单光配置相比,双光SERF磁力仪可以实现更高的灵敏度,并且不需要额外的磁场调制,因此省略了采集系统中复杂的锁相放大器。这种装置更有利于实现小型化的全头脑磁图传感器阵列。     

用于零场核磁共振探测的无自旋交换弛豫原子磁力仪

研制了用于液体零场核磁共振探测的无自旋交换弛豫(SERF)铷原子磁力仪。通过实验测量原子的磁共振曲线,验证了磁力仪工作在SERF状态,且结果与理论相符。采用增加光强的方法提高磁力仪带宽,满足了液体零场核磁共振的带宽需求,磁力仪在20~300Hz频率范围内的灵敏度低于18fT/Hz1/2。用基于磁力仪研制的液体零场核磁共振装置对甲酸样品进行测量,得到了13 C标记的甲酸的零场核磁共振谱,验证了磁力仪的可用性。     

抽运光频率对全光Cs原子磁力仪灵敏度的影响

全光铯(Cs)原子磁力仪是一种高灵敏度弱磁检测装置,核心器件Cs原子气室中通常充入适量的缓冲气体避免被极化原子扩散至器壁引起壁碰撞弛豫,同时缓冲气体压强值将影响抽运光的工作频率。介绍了全光Cs原子磁力仪的工作原理,分析了Cs原子气室中充入1.333×104Pa He缓冲气体时,抽运光工作频率对原子磁力仪灵敏度的影响,并采用速率方程计算了不同抽运光频率下的原子极化率。当抽运光频率锁定在Cs原子D1线F=3→F′=4共振线,检测光频率锁定在Cs原子D2线F=4→F′=5共振线时,原子磁力仪可达到最佳灵敏度。     

激光抽运-检测型原子磁力仪对交变磁场的测量北大核心CSCD

交变磁场作为磁场一种特殊的存在形式,有着广泛的应用和学术价值,而现阶段没有行之有效的方法对交变磁场进行绝对测量。抽运-检测型原子磁力仪具有量程宽、灵敏度高、能准确反映磁场真实特性,在磁场测量及标定中具有非常重要的意义。通过对抽运-检测型原子磁力仪在交变磁场激励下作用机理研究,对实验装置进行改进,实现抽运-检测型原子磁力仪对交变磁场的绝对测量,在Z轴方向上实现了背景磁场40000 nT,频率为100 Hz、磁场强度幅值为1000 nT的交变磁场测量;在Y轴方向上实现了背景磁场1000 nT,频率为20 Hz、磁场强度幅值为500 nT的交变磁场测量。测量结果表明该实验装置适用于低频、弱磁场强度交变磁场的测量,该方法为交变磁场的测量和标定提供一种切实可行的技术手段。     

基于MEMS技术的光泵原子磁力仪发展与应用北大核心

综述了光泵原子磁力仪的发展过程及技术指标,介绍了基于MEMS的光泵原子磁力仪的现状,总结了光泵原子磁力仪的主要应用。对基于MEMS技术的光泵原子磁力仪的发展应用前景提出了建议,基于MEMS技术的光泵原子磁力仪在未来也会成为空间磁场分布测量的重要手段,为航空、船舶、医疗诊断等领域提供重要支撑。微型化的原子磁力仪甚至有望集成到家用医疗设备或嵌入到可穿戴设备中去,这将成为原子磁力仪进入消费电子领域的突破口,基于MEMS技术的光泵原子磁力仪会成为新一代磁测量产品的标志,成为磁测量民用市场不可替代的产品。     

Cs原子磁力仪共振谱线宽度的研究

介绍了Cs原子无自旋交换弛豫磁力仪(Cs-SERFM)的工作原理;分析了Cs泡温度105℃条件下,缓冲气体He的压强对Cs原子横向弛豫及线宽的影响,给出了惰性气体He的最佳压强为350×133.3 Pa;讨论了共振谱线的宽度与温度之间的关系,在105℃时Cs-SERFM谱线宽度仅为3.7 Hz。     

基于法拉第旋转检测的铷原子磁力仪研究

基于线偏振光在充有被极化的铷原子的气室内传播时,在磁场的作用下会发生法拉第旋转这一现象,实现了一种基于法拉第旋转检测的铷原子矢量磁力仪。分析了它的工作原理,并测试了它对不同磁场的响应。测试结果表明,磁力仪灵敏度为1pT/Hz,测量范围为±60 n T,响应带宽为48 Hz。进一步研究了调制磁场和工作温度对铷原子磁力仪性能的影响,并提出了一些提高性能的方法。     

Cs(7DJ)+H2的反应与非反应碰撞转移截面的测定

利用激光泵浦-吸收技术,研究了在样品池中的Cs(7D_J)+H₂→CsH[X¹∑+(v″=0)]+H光化学反应过程。双光子激发Cs-H₂混合蒸气中Cs原子至7²D态,荧光中除有泵浦能级发生的直接荧光外,还包含由精细结构碰撞转移产生的敏化荧光,CsH分子是由7D原子与H₂间的三体碰撞反应产生的。利用780 nm激光测量了CsH X¹∑+(v″=0→v″=21)吸收带。△Ⅰ′和△Ⅰ″分别表示泵浦7D_3/2和7D_5/2时的吸收光强。解速率方程组,得到7D_3/2→7D_5/2和7D_5/2→7D_3/2精细结构转移截面分别为(1.3±0.3)×10^-14和(9.8±2.0)×10^-15cm²。从7D_J碰撞到7D以外态的截面分别为(4.0±1.0)×10^-15(对J=3/2)和(3.6+0.9)×10^-15cm²(对J=5/2)。Cs(7D_J)+H₂→CsH+H的反应截面分别是(1.4±0.5)×10^-16(J=3/2)和(1.1±0.4)×10^-16cm²(J=5/2),7D_3/2与H₂的反应活动...更多性大于7D_5/2。     

基于原子自由进动的光缩效应实验研究

在一定磁场下,自旋交换碰撞是原子磁力仪保持相干的一个主要限制因素,直接影响磁力仪能够达到的探测灵敏度。光缩效应可以对自旋交换碰撞展宽进行抑制,之前对光缩效应的观测是基于泵浦激光和射频场连续工作的方式,但会对原子共振展宽产生额外的影响。基于脉冲泵浦式原子磁力仪,通过极大限度地减小原子破坏性碰撞和外磁场空间不均匀性对共振展宽的影响,实现了对光缩效应的直接实验观测和验证。脉冲泵浦的方式有利于原子高极化度的实现,研究光缩效应对探索脉冲泵浦原子磁力仪的灵敏度极限具有重要意义。     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

A rigorous proof of MIMO channel capacity’s increase with antenna number

It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity in the multiple-input multiple-output（MIMO） communication systems. In this letter, a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receiving antennas. The proof is based on the famous capacity formula of Foschini and Gans with matrix theory.     

Teleportation of an arbitrary unknown N-qubit entangled state under the controlling of M controllers

A new quantum protocol to teleport an arbitrary unknown N-qubit entangled state from a sender to a fixed receiver under M controllers(M < N) is proposed. The quantum resources required are M non-maximally entangled Greenberger-Home-Zeilinger (GHZ) state and N-M non-maximally entangled Einstein-Podolsky-Rosen (EPR) pairs. The sender performs N generalized Bell-state measurements on the 2N particles. Controllers take M single-particle measurement along x-axis, and the receiver needs to introduce one auxiliary two-level particle to extract quantum information probabilistically with the fidelity unit if controllers cooperate with it.     

Diode-end-pumped Nd:YVO4/LBO lasers with 4.2W continuous-wave output at 457 nm

A continuous-wave (CW) 457 nm blue laser operating at the power of 4.2 W is demonstrated by using a fiber coupled laser diode module pumped Nd: YVO4 and using LBO as the intra-cavity SHG crystal With the optimization of laser cavity and crystal parameters, the laser operates at a very high efficiency. When the pumping power is about 31 W, the output at 457nm reaches 4.2 W, and the optical to optical conversion efficiency is about 13.5% accordingly. The stability of the out putpower is better than 1.2% for 8 h continuously working.     

Call for Papers

正Wireless Body-area Networks The last decade has witnessed the convergence of three giant worlds:electronics,computer science and telecommunications.The next decade should follow this convergence in most of our activities with the generalization of sensor networks.In particular with the progress in medicine,people live longer and the aging of population will push the development of wireless personal networks