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Nonreciprocal transmission of multi-band optical signals in thermal atomic systems

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Chinese Optics Letters 2022年第1期20卷 148-154页

作者： Shengfa Fan Yihong Qi Yueping Niu Shangqing Gong School of Physics East China University of Science and TechnologyShanghai 200237China School of Materials Science and engineering East China University of Science and TechnologyShanghai 200237China

Multi-band signal propagation and processing play an important role in quantum communications and quantum *** recent years,optical nonreciprocal devices such as an optical isolator and circulator are proposed via various configurations of atoms,metamaterials,nonlinear waveguides,*** this work,we investigate all-optical controlled nonreciprocity of multi-band optical signals in thermal atomic *** introducing multiple strong coupling fields,nonreciprocal propagation of the probe field can happen at some separated frequency bands,which results from combination of the electromagnetically induced transparency(eit) effect and atomic thermal *** the proposed configuration,the frequency shift resulting from atomic thermal motion takes converse effect on the probe field in the two opposite *** this way,the probe field can propagate almost transparently within some frequency bands of eit windows in the opposite direction of the coupling ***,it is well blocked within the considered frequency region in the same direction of the coupling fields because of destruction of the *** selectable optical nonreciprocity and isolation for discrete signals may be greatly useful in controlling signal transmission and realizing selective optical isolation functions.

关键词： optical nonreciprocity atomic thermal motion electromagnetically induced transparency multi-band

The generation of broadband weak-light rogue waves in a coherently prepared atomic system

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The generation of broadband weak-light rogue waves in a cohe...

Ultrasound-Guided Weighting of Regularization Parameters for eit Image Reconstruction

第十八届全国量子光学学术会议

作者：关佳 C.J.Zhu Y.P.Yang 同济大学 School of Physics Science and engineering Tongji University

Optical rogue waves have become a research hotspot in the field of optical research due to its huge steep waveform and the unobserved traveling wave characteristics. It has been studied and applied in fiber optic systems and electromagnetically induced transparency（eit） systems, but it has been a difficult problem in the stable and non-destructive generation of optical rogue waves under weak-light conditions because of the low nonlinear characteristics of fiber-optic systems[1]and the complex structure and magnetic field interference of eit systems[2]. We propose the formation of weak-light rogue waves by using a coherently prepared three-level atom system. In this new scheme, two lower states are coherently prepared prior to the injection of a strong pump field and a weak quantum probe field, not only holds characteristics of both eit-based system and the active Raman gain（ARG） based system, but also can acts as a two-photon-broadband phase shifter without gain or loss, an attenuator/amplifier with zero phase shift or low noise probe field phase shifter[3]. We show that the weak-light rogue waves with wide probe light frequency range can be formed in this system. Meanwhile, this system is simple and easy to fabricate since it is a tunable and elastic scheme. In other words, the population of the ground states are unnecessary to equal 50-50 percent, and the frequency range of the probe light is also wide. Besides, there is no Zeeman division because of the absence of the external magnetic field. These results are of great significance to the experimental acquisition and practical research of weak-light Rogue wave, which have important applications in light information transmission with weak light, large capacity and high fidelity.

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Ultrasound-Guided Weighting of Regularization Parameters for...

Electrical impedance tomography using adaptive mesh refinement

第三十九届中国控制会议

作者： Jiaqi Han Shu Zhao Shangjie Ren Feng Dong Tianjin Key Laboratory of Process Measurement and Control School of Electrical and Information Engineering Tianjin University Institute of Biomedical engineering Chinese Academy of Medical Sciences and Peking Union Medical College

Electrical impedance tomography（eit） has the advantages of non-invasion,non-radiation,low cost and sustainable detection,and is suitable for clinical real-time ***,the inverse problem of eit is seriously ill-conditioned and is usually solved by *** the inverse problem of eit is solved by Tikhonov regularization,the selection of regularized parameters has a great influence on the quality of the reconstructed image and proposes a method to guide the selection of regularized parameters using B-mode ultrasonic *** inclusion information is extracted from B-mode ultrasound scanning images and used as the basis for selecting regularization *** simulation experiment proves that the regularization parameter adjusted by B-mode ultrasound information has a good reconstruction effect on the imaging boundary.

关键词： Electrical impedance tomography image reconstruction regularized parameters weighting ultrasonic

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Journal of Shanghai University(English Edition) 2006年第3期10卷 228-232页

作者：严佩敏王朔中 School of Communication and In formation Engineering Shanghai University Shanghai 200072 P . R . China

In electrical impedance tomography （eit）, distribution of the internal resistivity or conductivity of an unknown object is esti- mated using measured boundary voltage data induced by different current patterns with various reconstruction algorithms. The reconstruction algorithms usually employ the Newton-Raphson iteration scheme to visualize the resistivity distribution inside the object. Accuracy of the imaging process depends not only on the algorithm used, but also on the scheme of finite element discretization. In this paper an adaptive mesh refinement is used in a modified reconstruction algorithm for the regularized Err. The method has a major impact on efficient solution of the forward problem as well as on achieving improved image resolution. Computer simulations indicate that the Newton-Raphson reconstruction algorithm for Err using adaptive mesh refinement performs better than the classical Newton-Raphson algorithm in terms of reconstructed image resolution.

关键词： electrical impedance tomography mesh refinement reconstruction algorithm exponentially weighted least square criterion..

Experimental Study of Detection of Brain Tissue with Electrical Impedance Tomography after Cerebral Ischemic

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Chinese Journal of Biomedical engineering(English Edition) 2017年第2期26卷 75-81页

作者： CHEN Chao-shuang FU Feng LI Bing LIU Wen-bo XU Shi-wei TAO Feng SHI Xue-tao YANG Lin FEI Zhou DONG Xiu-zhen Department of Biomedical engineering Fourth Military Medical University Department of Neurosurgery Xijing Hospital Fourth Military Medical University

Intracerebral haemorrhage(ICH), which has rapid attack and high death rate, usually leads to bad outcomes. Poor prognosis of this disease is primarily due to the difficulty of early discovery. Early detection or diagnosis would significantly reduce the rate of disability and mortality, and improve the prognosis of the patients. The purpose of this paper is to testify electrical impedance change and detection of brain tissue after cerebral ischemic with electrical impedance tomography. In this study, electrical impedance tomography(eit) was applied to detect the onset of modeled on rabbits in real time, ICH model group were injected collagenase in the Corpus Striatum while rabbits in control group were injected the same volume of saline with collagenase. The subsequent process was monitored continuously by system of electrical impedance tomography;the rabbits were sacrificed by intravenous injection of over dose of hydration chlorine aldehyde, and then taken into being scanned by computed tomography(CT) with a resolution of l mm within 10 min after death. After that, the brains of the rabbits were taken out,fixed and cut into slices to detect the changes of brain tissue. We found that onedimensional impedance and two-dimensional(2D) images of electric resistance of brain of the rabbits pretreated with collagenase obviously changed after injection and the hemorrhage could be found in the slices of brain and there were changes in the model rabbits group not only the electric resistance but also the brain *** quantitative index can't be provided by detection of intracerebral hemorrhage in rabbits with electrical impedance tomography's at this stage, cerebral hemorrhage can cause brain electrical impedance characters of the change, the completed experiments suggest that electrical impedance tomography(eit) may become an effective technique to detect ICH.

关键词： eit ICH early detection two-dimensional image one-dimensionalimpedance

In vivo Detection and Imaging of Intraventricular Hemorrhage in Neonatal Piglets Using Electrical Impedance Tomography

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Chinese Journal of Biomedical engineering(English Edition) 2018年第2期27卷 57-67页

作者： LI Yan-dong SHI Xue-tao DAI Meng YOU Fu-sheng XU Can-hua FU Feng LIU Rui-gang WANG Liang GAO Guo-dong DONG Xiu-zhen School of Biomedical engineering Fourth Military Medical University Department of Neurosurgery Tangdu Hospital Fourth Military Medical University

Intraventricular hemorrhage(IVH) is one of the most severe medical emergencies in neurosurgery. Early detection or diagnosis would significantly reduce the rate of disability and mortality, and improve the prognosis of the *** present medical imaging techniques have high sensitivity to identify bleeding, the use of an additional, non-invasive imaging technique capable of continuously monitoring IVH is required to prevent contingent bleeding or re-bleeding. In this study, electrical impedance tomography(eit) was applied to detect the onset of IVH modeled on 6 piglets in real time, with the subsequent process being monitored continuously. The experimental IVH model was introduced by one-time injection of 2 ml fresh autologous arterial blood into the ventricles of *** showed that resistivity variations within the brain caused by the added blood could be detected and imaged in vivo using the eit method, and the magnitude and the size of region of interest on eit images may be linearly associated with the volume of the blood. In conclusion, eit has unique potential for use in clinical practice to provide invaluable real-time neuroimaging data for IVH after the improvement of electrode design, anisotropic realistic modeling, and instrumentation.

关键词： electrical impedance tomography intraventricular hemorrhage imaging monitor

Light-shift induced by two unbalanced spontaneous decay rates in eit(CPT)spectroscopies under Ramsey pulse excitation

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Chinese Physics B 2021年第8期30卷 322-326页

作者： Xiaoyan Liu Xu Zhao Jianfang Sun Zhen Xu Zhengfeng Hu The Key Laboratory of Quantum Optics Shanghai Institute of Optics and Fine MechanicsChinese Academy of SciencesShanghai 201800China Center of Materials Science and Optoelectronics engineering University of the Chinese Academy of SciencesBeijing 100049China Department of Physics Shanghai UniversityShanghai 200444China CAS Center for Excellence in Ultra-intense Laser Science Shanghai 201800China

Light shift is important and inevitably affects the long-term stability of an atomic *** this work,considering two unbalanced branches of the spontaneous decay rate in a three-level system,we studied the frequency shifts of electromagnetically induced transparency(eit)and coherent population trapping(CPT)clocks operating under the pulse sequence regime by numerically solving the Liouville density matrix *** results show that the frequency shifts are larger when the two branches of spontaneous emission rate are not equal compared to the equal *** addition,in eit-Ramsey,the effect of the unbalanced branches of the spontaneous decay rate and relaxations of low-energy states on the frequency shift is greater than that of Rabi *** CPT-Ramsey,the relaxations of low-energy states play a dominant role in frequency shift.

关键词： atom clock light shfit laser-atom interaction quantum optics

Sensitivity-Controlled Electrical Impedance Tomography for Abdomen Lesion Imaging

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Sensitivity-Controlled Electrical Impedance Tomography for A...

Experiments and SPICE simulations of double MgO-based perpendicular magnetic tunnel junction

第37届中国控制会议

作者： Hao Yu Shangjie Ren Feng Dong Tianjin Key Laboratory of Process Measurement and Control School of Electrical and Information Engineering Tianjin University

Electrical Impedance Tomography（eit） reconstructs the conductivity distribution inside a domain through the measured voltage on the *** owns the advantages of non-invasive,nonradioactive and long term of monitoring,and thus has wide application *** improve the resolution of eit in detecting lesions in human abdomen,a numerical model was established according to the abdomen anatomical structure.A novel abdomen domain discretization method was proposed based on the sensitivity distribution inside abdomen domain and optimized polygon meshes were obtained for eit inverse *** with the commonly used uniform meshes,the optimized polygon meshes consider the structure and conductivity of abdomen as prior information,and thus can improve the imaging quality and convergence.

关键词： electrical impedance tomography human abdomen inverse problem optimized polygon meshes

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Chinese Physics B 2021年第4期30卷 518-525页

作者： Qiuyang Li Penghe Zhang Haotian Li Lina Chen Kaiyuan Zhou Chunjie Yan Liyuan Li Yongbing Xu Weixin Zhang Bo Liu Hao Meng Ronghua Liu Youwei Du China Electric Power Research Institute Beijing 100192China School of Physics Nanjing UniversityNanjing 210093China School of Science Nanjing University of Posts and TelecommunicationsNanjing 210023China School of Electronics Science and engineering Nanjing UniversityNanjing 210093China State Grid Tianjin Electric Power Company Tianjin 300384China Key Laboratory of Spintronics Materials Devices and Systems of Zhejiang ProvinceZhejiang 311300China

We investigate properties of perpendicular anisotropy magnetic tunnel junctions(pMTJs) with a stack structure MgO/CoFeB/Ta/CoFeB/MgO as the free layer(or recording layer),and obtain the necessary device parameters from the tunneling magnetoresistance(TMR) *** loops and current-driven magnetization switching *** on the experimental results and device parameters,we further estimate current-driven switching performance of pMTJ including switching time and power,and their dependence on perpendicular magnetic anisotropy and damping constant of the free layer by SPICE-based circuit *** results show that the pMTJ cells exhibit a less than 1 ns switching time and write energies <1.4 pJ;meanwhile the lower perpendicular magnetic anisotropy(PMA) and damping constant can further reduce the switching time at the studied range of damping constant α <***,our results demonstrate that the pMTJs with the thermal stability factor■73 can be easily transformed into spin-torque nano-oscillators from magnetic memory as microwave sources or detectors for telecommunication devices.

关键词： magnetic tunnel junctions magnetic tunnel junction(MTJ)model switching time spin torque nano-oscillator