Discrete dispersion of optical pulses on nonlinear-induced moving lattice

A theory of the interaction of an optical pulse with a concurrently moving lattice created in a nonlinear medium by a biharmonic pump wave is presented. Regimes for the partitioning of a solitary signal into subpulses, trapping a pulsed signal into a parametric soliton, and eliminating the lattice dispersion of pulses with a certain velocity are found.     

Relevance of ferromagnetic correlations for the electron spin resonance in Kondo lattice systems

Electron spin resonance (ESR) measurements of the ferromagnetic (FM) Kondo lattice system CeRuPO show a well defined ESR signal which is related to the Ce3+ magnetism. In contrast, no ESR could be observed in the antiferromagnetic (AFM) homologue CeOsPO. Additionally, we detect an ESR signal in ferromagnetic YbRh while it was absent in a number of Ce or Yb intermetallic compounds with dominant AFM exchange. Thus, the observation of an ESR signal in a Kondo lattice is neither specific to Yb nor to the proximity to a quantum critical point, but seems to be connected to the presence of FM fluctuations. These conclusions not only provide a basic concept to understand the ESR in Kondo lattice systems even well below the Kondo temperature (as observed in YbRh2Si2) but point out ESR as a prime method to investigate directly the spin dynamics of the Kondo ion.     

Noise induced resonance phenomena in coupled map lattices

We analyse different types of resonance phenomena that can occur in a coupled map lattice in the presence of noise with a subthreshold signal. The onsite dynamics considered here is different from previous such studies, namely, a bimodal cubic map capable of bistability in its dynamics. In addition to the resonance observed in the temporal iterates (the conventional stochastic resonance), we establish the possibility of resonance patterns in spatial sequences along the lattice, which we refer to as “Lattice Stochastic Resonance”. The characterising features of both are investigated in detail, under different types of signals with nearest neighbour coupling between lattice points. Possible practical applications are in signal detection, image processing and in communication networks.     

Reflection of light from an induced moving lattice

The reflection, refraction, and penetration of a signal optical pulse upon interaction with a pumping-induced moving lattice in media with cubic nonlinearity has been investigated. Numerical simulation is performed for different lattices and signal pulses.     

Feedback control of atomic motion in an optical lattice

We demonstrate a real-time feedback scheme to manipulate wave-packet oscillations of atoms in an optical lattice. The average position of the atoms in the lattice wells is measured continuously and nondestructively. A feedback loop processes the position signal and translates the lattice potential. Depending on the feedback loop characteristics, we find amplification, damping, or an entire alteration of the wave-packet oscillations. Our results are well supported by simulations.     

诊断LiF单晶弹性变形的瞬态X射线衍射

利用瞬态X射线衍射技术对LiF单晶沿晶向[100]方向冲击加载的晶格变形进行了诊断研究。实验在神光Ⅱ装置的球形靶上进行,北四路激光驱动Cu靶获得的类He线作为X射线背光源,第九路为加载光源,对大小为7mm×7mm、厚300μm的受激光加载的LiF单晶衍射,实验获得了LiF单晶晶面(200)压缩和未压缩状态的衍射信号。实验结果表明:LiF单晶在激光沿[100]方向冲击加载下,晶格发生了弹性变形,(200)晶面间距变小,衍射线上移,晶格压缩量为11%;该瞬态X射线衍射技术可用于冲击加载下的微观动态响应特性测量。     

Echo responses of an ensemble of cold atoms in optical lattices

The dynamics of an ultracold dilute boson gas in an optical lattice is described in the framework of the Bose-Hubbard model in which the parameters of the system are controlled by light. Within this model, an ensemble of Bose-Einstein condensates trapped in cells of a double optical lattice generates an echo response in the quantum-mechanical probability current. The echo signal is excited by biharmonic radiation pulses under two-photon (Raman) resonance conditions. The time profile of the echo signal and the role played by the inhomogeneous broadening and the interaction of atoms in the formation of the boson echo are discussed.     

Discrete diffraction and waveguiding of optical beams in a cascade-induced lattice

Regularities of anisotropic discrete diffraction in a cascade-induced lattice formed by two crossed pump waves in a quadratically nonlinear medium have been studied. The transition from diffraction of a signal beam in free space to discrete diffraction with further capture into a waveguide in a defocusing lattice with an increase in the pump wave intensity has been traced. Diffraction-free propagation of a tilted beam is described.     

Reflectivity function reconstruction using adaptive lattice deconvolution technique

Deconvolution of ultrasonic echo signals improves resolution and quality of ultrasonic images. The problem of reconstructing the reflectivity of a biological tissue is examined by adaptive lattice deconvolution of the echo ultrasound signals. The simulation of the signal formation process in an ultrasonic-echo scan line in noisy conditions is estimated. The reflectivity of a biological tissue is estimated as cross-correlation coefficients between forward and backward predication errors in each stage of the adaptive lattice filter.     

Influence of impurities on the dynamics and synchronization of coupled map lattices

The influence of impurities and defects on the dynamics and synchronization of coupled map lattices (CML) is studied. In the context of CML we define impurities as sites in the lattice which have another local dynamics that from the whole lattice and defects as sites in the lattice without any dynamics. We show that synchronization and spatial intermittence are obtained as a function of the number of impurities present on a one-dimensional lattice. We also derive an analytical condition for a signal to “transpose” an impurity. For open flow models, we show that not only the presence of the impurity but also its position along the lattice and its local dynamics can be used to manipulate the lattice in order to obtain a regular or irregular motion. We also show how defects can be used to store information in a lattice.     

Atomic Bloch-Zener oscillations and Stückelberg interferometry in optical lattices

We report on experiments investigating quantum transport and band interferometry of an atomic Bose-Einstein condensate in an optical lattice with a two-band miniband structure, realized with a Fourier-synthesized optical lattice potential. Bloch-Zener oscillations, the coherent superposition of Bloch oscillations and Landau-Zener tunneling between the two bands, are observed. When the relative phase between paths in different bands is varied, an interference signal is observed, demonstrating the coherence of the dynamics in the miniband system. Measured fringe patterns of this Stückelberg interferometer allow us to interferometrically map out the band structure of the optical lattice over the full Brillouin zone.     

铱掺杂溴化银微晶的瞬态光电导研究

研究在77K时，铱掺杂溴化银微晶瞬态光电导（TPC）的信号强度和衰减时间与铱掺杂浓度间的关系。在溴化银微晶的制备过程中，IrCl6^3-作为掺杂剂加入，使溴化银微晶中的部分银离子所占据的晶格位被铱离子取代，在溴化银晶体中同时引入新的电子陷阱与空穴陷阱，增强了内部的电子空穴复合，使TPC的信号强度随铱离子掺杂浓度的增大而减小。     

Discrete diffraction in a cascade-induced anisotropic lattice

The features of anisotropic discrete diffraction in a cascade-induced lattice formed by two crossed pump waves in a quadratically nonlinear medium have been studied. The transition from the diffraction of a signal beam in free space to discrete diffraction with the further capture in a waveguide in a defocusing lattice by the increasing of the pump wave intensity has been traced.     

A new control method based on the lattice hydrodynamic model considering the double flux difference

A new feedback control method is derived based on the lattice hydrodynamic model in a single lane. A signal based on the double flux difference is designed in the lattice hydrodynamic model to suppress the traffic jam. The stability of the model is analyzed by using the new control method. The advantage of the new model with and without the effect of double flux difference is explored by the numerical simulation. The numerical simulations demonstrate that the traffic jam can be alleviated by the control signal.     

Generation of coherent phonons in opaque crystals: A radio engineering analogy

A model is proposed for generating coherent phonons by ultrashort laser pulses in opaque crystals. The model is based on the radio engineering analogy with two coupled RLC circuits, of which the first circuit corresponds to the electronic subsystem of the crystal and the second circuit corresponds to the lattice sub-system. It is demonstrated that this analogy makes it possible to describe a number of characteristic properties of coherent phonons and facilitates the separation of the contributions from the nonequilibrium charge carriers and the coherent lattice dynamics to the time-resolved reflection signal in opaque crystals.     

Interaction of a probe optical signal with a quasi-periodical sequence of high-power pump pulses

Interaction of a short optical pulse with a refractive index lattice induced in a nonlinear medium by quasi-periodic pulsed structures at close frequencies is investigated. Numerical simulation is performed for reflection, transmission, and multiplexing of the signal pulse into several subpulses for different induced lattices.     

Bursting synchronization in non-locally coupled maps

Neuron activity presents two timescales, a fast one related to action-potential spiking, and a slow timescale in which bursting takes place. Bursting activity in neuron ensembles can be synchronized, meaning the adjustment of the bursting phases due to coupling. We investigated bursting synchronization in a non-locally coupled lattice using a two-dimensional map to describe neuron activity. The coupling involves all sites in a lattice, the corresponding strength decreasing with the lattice distance in a power-law fashion. We observed bursting synchronization for wide intervals of the coupling parameters. We also investigated the bursting synchronization of the ensemble with an external time-periodic signal applied to one or more selected neurons.     

A phase transition in SU(5) lattice gauge theory in four dimensions

Monte Carlo simulations of the average action per plaquette are calculated for four-dimensional SU(5) gauge theory on a 3⁴ lattice. Evidence is found for a discontinuity in this order parameter which is a signal for a first-order phase transition.     

质子辐射下互补金属氧化物半导体有源像素传感器暗信号退化机理研究

对某国产0.5 μm工艺制造的互补金属氧化物半导体有源像素传感器进行了10 MeV质子辐射试验, 当辐射注量达到预定注量点时, 采用离线的测试方法, 定量测试了器件暗信号的变化情况. 试验结果表明, 随着辐射注量的增加暗信号迅速增大. 采用MULASSIS (multi-layered shielding simulation software)软件计算了电离损伤剂量和位移损伤剂量, 在与γ辐射试验数据对比的基础上, 结合器件结构和工艺参数, 建立了分离质子辐射引起的电离效应和位移效应理论模型, 深入分析了器件暗信号的退化机理. 研究结果表明, 对该国产器件而言, 电离效应导致的表面暗信号和位移效应导致的体暗信号对整个器件暗信号退化的贡献大致相当.     

Acoustical-photorefractive recording of acoustical oscillations

The process whereby acoustic waves are recorded in photorefractive piezoelectric crystals by means of the acoustophotorefractive effect is studied. Expressions are obtained for the electric fields and elastic displacements of the recorded holographic lattice. The kinetics of the recording of monochromatic waves and complex acoustic signals under the action of pulsed uniform illumination is studied. It is shown that in the case when a complex acoustic signal is recorded the signal recorded with short recording times is the derivative of the input signal.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 33–37, July, 1987.