Magneto-optical Kerr and Faraday effects in bilayer antiferromagnetic insulators

Control and detection of antiferromagnetic topological materials are challenging since the total magnetization vanishes.Here we investigate the magneto-optical Kerr and Faraday effects in bilayer antiferromagnetic insulator Mn Bi2Te4.We find that by breaking the combined mirror symmetries with either perpendicular electric field or external magnetic moment,Kerr and Faraday effects occur.Under perpendicular electric field,antiferromagnetic topological insulators(AFMTI)show sharp peaks at the interband transition threshold,whereas trivial insulators show small adjacent positive and negative peaks.Gate voltage and Fermi energy can be tuned to reveal the differences between AFMTI and trivial insulators.We find that AFMTI with large antiferromagnetic order can be proposed as a pure magneto-optical rotator due to sizable Kerr(Faraday)angles and vanishing ellipticity.Under external magnetic moment,AFMTI and trivial insulators are significantly different in the magnitude of Kerr and Faraday angles and ellipticity.For the qualitative behaviors,AFMTI shows distinct features of Kerr and Faraday angles when the spin configurations of the system change.These phenomena provide new possibilities to optically detect and manipulate the layered topological antiferromagnets.

Determination of the magnetic anisotropy constant of Cu/Fe/SiO_2/Si by a magneto-optical Kerr effect susceptometer

The magneto-optical Kerr effect susceptometry technique is proposed to determine the uniaxial magnetic anisotropy （UMA） constant Ku. The magnetic properties of Cu/Fe/SiO2/Si grown by dc magnetron sputtering were investigated. The in-plane uniaxial magnetic anisotropy was probed by the magneto-optical Kerr effect （MOKE）. The value of UMA, Ku = 2.5 x 103 J/m3, was simulated from the field dependence of ac susceptibility along the hard axis according to the Stoner-Wohlfarth （S-W） model, which is consistent with Ku = 2.7~ 103 J/m3 calculated from the magnetic hysteresis loops. Our results show that the magneto-optical Kerr effect susceptometry can be employed to determine the magnetic anisotropy constant owing to its high sensitivity.

Resonant magneto-optical Kerr effect induced by hybrid plasma modes in ferromagnetic nanovoids

With nanovoids buried in Co films, resonant structures were observed in spectra of polar magneto-optical Kerr effect（MOKE）, where both a narrow bandwidth and high intensity were acquired. Through changing the thickness of Co films and the lattice of voids, different optical modes were introduced. For a very shallow array of voids, the resonant MOKE was induced by Ag plasma edge resonance, for deeper ones, hybrid plasma modes, such as void plasmons in the voids, surface lattice plasmons between the voids, and the co-action of them, etc. resulted in resonant MOKE. We found that resonant MOKE resulted from the void plasmons resonance which possesses the narrowest bandwidth for the lowest absorption of voids. The simulated electromagnetic field（EF） distribution consolidated different effects of these three optical modes on resonant MOKE modulation. Such resonant polar MOKE possesses high sensitivity, which might pave the way to on-chip MO devices.

The subwavelength tuned magneto-optical Kerr effect in L1_0-FePt films with perpendicular magnetic anisotropy

For L10-FePt films with strong perpendicular anisotropy covered by arrays of hexagonal close-packed polystyrene spheres （PSSs）, fine structures are observed in magneto-optical Kerr rotation spectra in the visible spectral range. The reflection minima are found to be located at the same wavelengths as the Kerr rotation peaks. The Kerr rotation enhancement is attributed to the excitation of both the surface plasmon polariton in the dielectric PSS/metal interface and the guide waves （guide mode） in the PSS array. The two-dimensional PSSs/SiO2/FePt system exhibiting a tunable magneto-optical Kerr effect and a high perpendicular magnetic anisotropy will be helpful for designing and fabricating magneto-optics devices.

Influences of decoherence on the generation of a macroscopic superposition state using weak cross-Kerr effect

Considering a system in which a single photon and a coherent field propagate through a Kerr medium, when the weak cross-Kerr interaction between the coherent state and the single photon under decoherence is involved, this paper derives analytically a macroscopic superposition state by the superoperator method and investigates the influences of decoherence on the coherence properties of the obtained state. It finds that the macroscopic superposition state will experience evolution from a pure superposltion state to a mixed state in a dissipative environment and the Kerr effect makes the field display a periodic revival from decoherence for a short time.

Ultrafast Optical Kerr Effect of ConjugatedSilver Phenylacetylide Complex Oligomer

Silver phenylacetylide oligomer was found to exhibit prominent third-order nonlinear optical property, with susceptibility chi((3)) of 2.4x10(-14) esu (10(-4) mol/L in 1:1 dimethyl sulfoxide/CHCl3 mixed solution) and second-order hyperpolarizability gamma of 5.18x10(-32) esu via heterodyned ultrafast optical Kerr effect measurement. It existed mainly as 1:1 complex oligomers and polymers as characterized by mass spectroscopy and elemental analysis etc.

Study of magnetization reversal and anisotropy of single crystalline ultrathin Fe/MgO (001) film by magneto-optic Kerr effect

The magnetization reversal process of Fe/MgO （001） thin film is investigated by combining transverse and longi- tudinal hysteresis loops. Owing to the competition between domain wall pinning energy and weak uniaxial magnetic anisotropy, the typical magnetization reversal process of Fe ultrathin film can take place via either an ＂l-jump＂ process near the easy axis, or a ＂2-jump＂ process near the hard axis, depending on the applied field orientation. Besides, the hysteresis loop presents strong asymmetry resulting from the variation of the detected light intensity due to the quadratic magneto-optic effect. Furthermore, we modify the detectable light intensity formula and simulate the hysteresis loops of the Kerr signal. The results show that they are in good agreement with the experimental data.

Kerr effect and Kerr constant enhancement in vertically aligned deformed helix ferroelectric liquid crystals

In this article,we review recently achieved Kerr effect progress in novel liquid crystal（LC） material：vertically aligned deformed helix ferroelectric liquid crystal（VADHFLC）.With an increasing applied electric field,the induced inplane birefringence of LCs shows quadratic nonlinearity.The theoretical calculations and experimental details are illustrated.With an enhanced Kerr constant to 130 nm/V2,this VADHFLC cell can achieve a 2π modulation by a small efficient electric field with a fast response around 100 μs and thus can be employed in both display and photonics devices.

Surface Plasmon and Fabry-Perot Enhanced Magneto-Optical Kerr Effect in Graphene Microribbons

A single sheet of graphene exhibits the ability to turn polarization of light by several degrees in modest magnetic fields. Here we demonstrate that giant angle rotation in graphene in the terahertz range can be realized and further increased by the introduction of surface plasmon and constructive Fabry Perot interference with the supporting substrate. The maximum Kerr rotation angle is up to 15° in a single layer of graphene ribbons at 6 TPIz for the applied magnetic field 4 T. Such a magnification in magneto-optical Kerr effect can be realized in a fairly large incident angle.

Stark and Kerr Effects on the Dynamics of Moving N-Level Atomic System

We have investigated numerically the dynamics of quantum Fisher information (QFI) and quantum entanglement (QE) for N-level atomic system interacting with a coherent field in the presence of Kerr (linear and non-linear medium) and Stark effects. It is observed that the Stark and Kerr effects play a prominent role during the time evolution of the quantum system. The evolving quantum Fisher information (QFI) is noted as time grows under the non-linear Kerr medium contrary to the QE for higher dimensional systems. The effect of non-linear Kerr medium is greater on the QE as we increase the value of Kerr parameter. However, QFI and QE maintain their periodic nature under atomic motion. On the other hand, linear Kerr medium has no prominent effects on the dynamics of N-level atomic system. Furthermore, it has been observed that QFI and QE decay soon under the influence of Stark effect. In short, the N-level atomic system is found prone to the change of the Kerr medium and Stark effect for higher dimensional systems.

Quantum Fisher Information of Two-Level Atomic System under the Influence of Thermal Field, Intrinsic Decoherence, Stark Effect and Kerr-Like Medium

In this paper, we have proposed the numerical calculations to study the quantum entanglement (QE) of moving two-level atom interacting with a coherent and the thermal field influenced by intrinsic decoherence (ID), Kerr medium (non-linear) and the Stark effect. The wave function of the complete system interacting with a coherent and the thermal field is calculated numerically affected by ID, Kerr (non-linear) and Stark effects. It has been seen that the Stark, Kerr, ID and the thermal environment have a significant effect during the time evolution of the quantum system. Quantum Fisher information (QFI) and QE decrease as the value of the ID parameter is increased in the thermal field without the atomic movement. It is seen that QFI and von Neumann entropy (VNE) show an opposite and periodic response in the presence of atomic motion. The non-linear Kerr medium has a more prominent and significant effect on the QE as the value of the Kerr parameter is decreased. At smaller values of the non-linear Kerr parameter, the VNE increases, however, QFI decreases, so QFI and VNE have a monotonic connection with one another. As the value of the Kerr parameter is increased, the effect of non-linear Kerr doesn’t stay critical on both QFI and QE. However, a periodic response of QE is seen because of the atomic movement which becomes modest under natural impacts. Moreover, it has been seen that QFI and QE rot soon at the smaller values of the Stark parameter. However, as the value of the Stark parameter is increased, the QFI and QE show periodic response even when the atomic movement is absent.

基于Kerr地基模型单井降水邻近管线变形计算方法

为了研究单井降水对邻近管线的影响,基于Kerr地基模型结合两阶段法提出了一种单井降水引起邻近管线竖向变形的计算方法。在第一阶段采用有效应力原理与Dupuit假定计算出降水引起邻近管线受到的附加应力,第二阶段将管线视作搁置在三参数Kerr地基上Euler-Bernoulli梁,以此模拟管线与土的相互作用进而推导出管线的竖向位移。通过与原位降水试验及Winkler模型的结果进行对比,验证了所提方法的准确性,并进一步分析了土体弹性模量、渗透系数、管-井间距以及水位降深变化对管线竖向位移的影响。分析结果表明:所采用的Kerr地基模型考虑了土体变形的连续性,相比Winkler地基模型更具优越性;土体渗透系数及管-井间距对管线变形影响较小,而土体弹性模量与降水井内水位降深影响较大;土体弹性模量减小、水位降深增大均导致管线变形明显增大,且易引起管线位移超过允许值,应针对相应因素采取防控措施。

Effects of Homogeneous Plasma on Strong Gravitational Lensing of Kerr Black Holes

Considering the Kerr black hole surrounded by a homogeneous unmagnetized plasma medium, we study the strong gravitational lensing on the equatorial plane of the Kerr black hole. It is found that the presence of the uniform plasma can increase the photon-sphere radius r_{／rm ps}, the coefficients ／bar{a} and ／bar{b}, the angular position of the relativistic images （／theta_{／infty}）, the deflection angle ／alpha（／theta） and the angular separation s. However, the relative magnitude r_{／rm m} decreases in the presence of the uniform plasma medium. It is also shown that the impact of the uniform plasma on the effect of strong gravitational lensing becomes smaller as the spin of the Kerr black hole increases in the prograde orbit （a〉0）. In particular, for the extreme black hole （a=0.5）, the effect of strong gravitational lensing in the homogeneous plasma medium is the same as the case in vacuum for the prograde orbit.

谐振式光学陀螺噪声抑制技术研究现状(特邀)

谐振式光学陀螺仪利用光学谐振腔在时空上对光波极强的局域增强效应,有望成为兼具高精度和小体积的光学陀螺。然而,谐振式陀螺转动产生的Sagnac效应相对微弱,容易受到陀螺系统内非互易性以及互易性噪声的干扰,成为其精度提升的瓶颈。在陀螺的小型化过程中这一问题更加凸显。因此,对谐振式光学陀螺仪进行噪声抑制显得尤为重要。本文详细综述了谐振式光学陀螺中非互易性和互易性两大类噪声的原理及其抑制方法,总结了该领域近来年的研究现状及未来挑战与发展趋势,为我国谐振式光学陀螺发展提供参考。

基于Kerr效应的绝缘子表面电场在线测量系统

为了有助于快脉冲功率装置中真空绝缘子的正确设计,避免其沿面闪络,研制了1套基于Kerr效应的可以在线测量快脉冲高电压作用下的真空绝缘子表面电场的电光测量系统。该测量系统由基于Marx发生器和脉冲形成线的快脉冲高电压源(100ns,200～350kV)、基于Nd:YAG倍频脉冲激光器的探测光源(532nm,8ns)、抗强电磁干扰的同步控制系统、被测中空薄壁绝缘子及Kerr效应单元、相位差检测系统(Mach-Zehnder干涉仪)等部分构成。在分析了快脉冲高电压作用下在线测量的必要性后介绍了该测量系统各部分的组成、工作原理、运行参数及初步实验结果。

基于Kerr效应法的油纸复合绝缘交直流复合电场测量

油纸复合绝缘作为换流变压器阀侧绕组的主绝缘形式,在正常工况下同时承担着交、直流复合电压,阀侧绕组的电场分布比普通电力变压器更为复杂,而目前的仿真研究均缺乏有效的试验验证。本文基于变压器油的Kerr效应,搭建了油纸绝缘结构下光学空间电场的二维测量平台,实现了变压器油中电场的在线分布式测量。针对双层纸板的交叠绝缘结构,实际测量不同交直流比例电压下,交、直流电场的分布特性。试验结果表明:①交流电场分布具有明显的结构对称特性,且油中各处交流电场与外施交流电压保持线性关系。②直流电场分布不具有对称性。在正极性直流电压下,纸板覆盖上电极的单层纸板区域电场远小于纸板覆盖下电极的单层纸板区域,且直流电场强度不随外施直流电压线性增长。不同位置处空间电荷积聚的差异是直流电场分布非对称性的主要原因。

基于Kerr电光效应的冲击电压下液体电介质空间电荷高速CCD测量

空间电荷的存在直接影响液体电介质的绝缘击穿性能,为了更好地研究空间电荷的动态变化过程,建立了基于Kerr电光效应的冲击电压下液体电介质空间电荷的高速电荷耦合器件(CCD)测量系统。运用高精度光电传感器的测量方法,得到了室温下液体碳酸丙烯酯的Kerr常数。进而通过高速CCD的动态光电测量,并结合图像处理技术,求取了冲击电压下平行板铜电极间电场和空间电荷的动态分布曲线。实验研究表明:在平行板铜电极间,当液体介质中电场达到一定程度时会出现空间电荷的注入与输运,使得极间电场呈现出中间高两边低的分布情况。另外还分析了空间电荷的分布和输运对液体绝缘特性的影响,该研究为分析冲击电压作用下液体介质中空间电荷的产生机制及空间电荷对流注放电的影响奠定了基础。

减少Kerr效应法在油纸绝缘结构中直流电场测量误差的方法

Kerr效应法是液体电介质中电场测量的有效方法,但利用该方法在油纸复合绝缘结构中的直流电场准确测量一直是电介质中电场测量的难点。为此,基于Kerr效应法搭建了一套在线非接触式的液体电介质中光学电场测量系统,分析了引起测量系统误差的主要原因,提出了减小测量误差的方法。通过加长电极和边缘绝缘包覆处理,可将电极边缘效应相对误差减小至1.3%;通过光学器件光学特性的标定,修正了器件非理想因素的误差;通过对激光器噪声的统计分析,合理选取了交流调制电源的频率,提高了测量系统的信噪比,可将激光管同频噪声干扰所导致的直流电场测量相对误差减小到0.86%,交流电场测量相对误差减小到1.6%。经过试验测定,整个测量系统直流电场强度测量灵敏度可达到20V/mm,总体相对误差<5.4%。

高Q Kerr介质腔中双模SU(1,1)相干态场与级联三能级原子相互作用的动力学特性

本文研究了一个位于高QKerr介质腔中初始时处于基态的级联三能级原子与双筷SU（1，1）相干态场相互作用系统中，Kerr效应对原子动力学行为和光场性质的影响.结果表明:随着Kerr效应增强，拉比振荡的回复周期缩短，双筷光场的压缩量总是减小，两模间的关联程度减弱，但非经典相关程度则存在增强的情形。