Dicke模型中的偏态信息

利用Wigner-Yanase偏态信息的定义,通过Dicke模型研究了数态光场的信息向原子系综的动力学转移.研究表明多个二能级原子组成的系综具备存储并释放光场信息的功能,但是,通过该模型光场信息只是部分地向原子系综转移.通过增加原子个数,光场信息的残留可以得到一定程度的抑制.     

纠缠相干光场对量子态最大演化速率的操控

考虑双模纠缠相干光场,将其中一束光场注入腔中与一个二能级原子发生共振相互作用,根据腔量子电动力学理论推导出原子系统的演化态.针对原子系统初始状态到目标演化态的动力学过程,利用量子速率极限时间概念来表征原子系统量子态的最大演化速率.通过调节双模纠缠相干光场的相干参数来操控原子系统量子态动力学过程中所能达到的最大演化速率.结果发现:与原子发生相互作用光场的相干参数在一定条件下可以对系统量子态的最大演化速率产生明显的影响;并且当该光场参数不能很好地来操控量子态的最大演化速率时,双模纠缠相干光场间的量子关联可以实现未参加相互作用光场参数对原子系统量子态最大演化速率的远程调控.     

压缩真空场与运动型三能级原子作用系统的光场压缩效应

采用求解Schr dinger方程和数值计算方法,研究了单模压缩真空场与运动Ξ型三能级原子相互作用过程中系统的动力学行为,讨论了系统参数对系统光场压缩效应的影响.数值计算结果表明:原子运动速度的大小决定了光场的压缩性质,当原子运动速度取较大值时,单模压缩真空场的初始压缩因子变化对光场的压缩性质产生明显影响.如选取适当的系统参数,就会产生完全压缩的光场.     

压缩真空场与运动Ξ型三能级原子作用系统的光场压缩效应

采用求解Schr(o)dinger方程和数值计算方法,研究了单模压缩真空场与运动Ξ型三能级原子相互作用过程中系统的动力学行为,讨论了系统参数对系统光场压缩效应的影响.数值计算结果表明:原子运动速度的大小决定了光场的压缩性质,当原子运动速度取较大值时,单模压缩真空场的初始压缩因子变化对光场的压缩性质产生明显影响.如选取适当的系统参数,就会产生完全压缩的光场.     

Kerr介质中耦合V型三能级原子与相干态光场作用场的量子性质

研究了Kerr介质中相干态光场与耦合V型三能级原子相互作用过程中场的量子性质.利用量子光学中光场与原子相互作用的耦合Tavis-Cummings模型,对系统的动力学过程进行了求解.讨论了系统初始状态、失谐量、原子间偶极相互作用强度及Kerr系数对光场量子性质随时间演化的影响.数值计算结果表明:初态中场的平均光子数比较小...     

Kerr介质中耦合V型三能级原子与相干态光场作用场的量子性质

研究了Kerr介质中相干态光场与耦合V型三能级原子相互作用过程中场的量子性质.利用量子光学中光场与原子相互作用的耦合Tavis-Cummings模型,对系统的动力学过程进行了求解.讨论了系统初始状态、失谐量、原子间偶极相互作用强度及Kerr系数对光场量子性质随时间演化的影响.数值计算结果表明:初态中场的平均光子数比较小时,光场能够展现出明显的量子效应|初始时刻原子激发态概率幅从小变大时,光场的反聚束效应变得越明显,而光场的压缩深度会先增大后减小|失谐量的变化对场的量子性质的影响不大,只是改变光场二阶相关函数和压缩参量振荡的周期|原子间耦合强度的增大使光场的反聚束效应减弱和光场的压缩深度变浅|Kerr系数的增大会增强光场的反聚束效应,而使光场的压缩深度变浅.     

Rabi模型的光场压缩

电路量子电动力学的实验实现了光与人造原子的超强耦合相互作用, 相互作用强度与光场频率在同一个数量级.在超强耦合区域, 著名的旋波近似失效, 因此系统的动力学必须用含有反旋波项的Rabi模型描述.本文研究Rabi模型中的光场压缩.数值模拟结果发现, 光场压缩不是随耦合强度线性增加, 而是在合适的超强区域获得最大值.同时, 我们还发现, 较小的反旋波项有助于提高光场压缩.所得结果有利于实验上在超强区域中制备所需的压缩态. 关键词： Rabi模型 超强耦合 光场压缩     

吸收型光学双稳态方程的时变分岔与动力学行为

用向量场的观点系统地研究吸收型光学双稳态方程的时变分岔问题及其动力学行为,探讨分岔转迁滞后现象中的内在规律性.当入射光场是常量时,用新方法分析了光学双稳态的存在性和临界慢化现象 当入射光场分别随时间线性慢变或周期慢变时,通过量级平衡给出分岔转迁的不同量级关系 当入射光场的振幅或频率随时间线性慢变时,研究了双稳时变系统的分岔和动力学行为,并揭示新的奇怪吸引子的出现. 关键词：     

两纠缠原子与相干态光场相互作用的动力学

采用时间演化算符和数值计算方法,研究了两全同二能级纠缠原子与相干态光场相互作用的动力学,结果表明:原子布居和偶极压缩特性与两原子体系纠缠度和相干态光场强度相关联.     

频率变化的光场对双J-C模型中原子-原子纠缠的调控

本文研究了频率随时间变化的光场对双J-C模型中原子--原子纠缠的动力学调控, 主要讨论了光场频率随时间作正弦变化和脉冲变化两种典型情况下, 原子--原子纠缠度随时间的演化特性. 当光场频率随时间作正弦变化时, 原子--原子纠缠度演化的周期、振幅与光场频率调制的振幅有关, 并随着调制振幅的增强而减小. 光场频率的正弦调制和脉冲调制均能使光场与原子的相互作用模式在共振和非共振之间发生变化, 直接影响原子--原子纠缠度的演化规律. 通过光场频率的调制可以实现原子--原子纠缠度的提高与稳定, 避免ESD现象的出现, 从而达到动态调控原子--原子纠缠的目的.     

Correlation of quadrature amplitude fluctuations during the intracavity generation of second harmonic

For the process of intracavity generation of the second harmonic, the dynamics of correlation of quadrature amplitudes fluctuations of the fundamental and the second harmonic modes is studied depending on the nonlinear coupling coefficient between the modes. It was shown that in this system the entangled states of field related to variables of quadrature amplitudes may be obtained depending on the nonlinear coupling coefficient. It was also shown that the entanglement of the states of field modes related to one quadrature amplitude may vanish depending on the value of nonlinear coupling coefficient, whereas the states of field modes related to the other quadrature amplitude stay entangled.     

铁镓Janus-Helmholtz换能器非线性驱动

利用磁路法理论分析了磁阻对铁镓驱动磁场的影响,结果表明磁路中无永磁体时铁镓驱动磁场是有永磁体时的5倍以上,结合铁镓材料近似线性区小的特点,提出了一种无偏场非线性驱动方式。首先利用帕德逼近方法近似铁镓材料的磁化过程,得到磁场强度与磁致伸缩应变的关系,进而得到驱动电信号表达式,在此基础上提出了铁镓换能器的非线性驱动模型。设计研制了无偏场铁镓Janus-Helmholtz换能器样机,通过振动特性实验分析验证非线性驱动模型的可行性,最后在水中测试了换能器的发射性能。测试结果表明,采用无偏场非线性驱动的换能器在驱动电流为9.4 A时,声源级可达到198.2 dB,相对于永磁偏置磁场的换能器,声源级高了4 dB,发射性能得到了明显的提升。     

Temperature field of dielectric films under continuous ion-beam irradiation

In the present study, we theoretically examine the formation process of the steady-state temperature field in dielectrics under irradiation with a continuous ion beam in air with allowance for the temperature dependence of thermophysical quantities. Analytical expressions for the temperature field were obtained. An interconnected system of nonlinear algebraic equations for the steady-state temperatures at the front (irradiated) and rear surfaces of the sample, and the steady-state temperature at the interface between the ion-damaged and non-damaged region was obtained; by numerical solution of this system, a nonlinear dependence of the mentioned temperatures on the characteristics of incident ion flux was revealed.     

Acoustic cavitation mechanism: a nonlinear model

During acoustic cavitation process, bubbles appear when acoustic pressure reaches a threshold value in the liquid. The ultrasonic field is then submitted to the action of the bubbles. In this paper we develop a model to analyze the cavitation phenomenon in one-dimensional standing waves, based on the nonlinear code SNOW-BL. Bubbles are produced where the minimum rarefaction pressure peak exceeds the cavitation threshold. We show that cavitation bubbles appear at high amplitude and drastically affect (dissipation, dispersion, and nonlinearity) the ultrasonic field. This paper constitutes the first work that associates the nonlinear ultrasonic field to a bubble generation process.     

Resonance scattering and generation of oscillations by channeling nonlinear layered media

For the first time within the framework of a self-consistent analysis of the process of resonant scattering and generation of oscillations by a channeling nonlinear layer it is shown that the imaginary part of the nonlinear component of the permittivity, induced by the intensity of the incident field, takes both positive and negative values along the height of the layer. The variation of this quantity characterizes the loss of energy in the nonlinear medium which is spent for the generation of the electromagnetic field at the higher harmonics. The consideration of a weak excitation field at a multiple frequency leads merely to an increase of the portion of generated energy.     

The kinetic theory of magnetic-field generation in a Langmuir plasma

We develop a two-timescale kinetic theory for the nonlinear generation process for a slow-timescale magnetic field in a hot collisionless Langmuir plasma. We show that the basic damping of this magnetic field is due to the collisionless skin effect.     

Nonlinear Thomson scattering from relativistic laser plasma interaction

As an electron oscillates in an intense laser field, it acquires a highly nonlinear motion and emits X-ray radiation by nonlinear Thomson scattering. In this paper we present a numerical and experimental analysis of this radiation. We show that this radiative process becomes dominant at relativistic laser intensities (a0>1), for which the laser light scatters off MeV electrons accelerated in the plasma.     

慢同步波行波管特性研究

 在传统行波管的放大过程中,随着电子纵向群聚的加深,由于空间电荷效应导致的非线性效应,影响了行波管的输出性能。介绍了一种新型的行波管并分析了其作用机理,分析了这种新型行波管慢波系统的结构及其色散特性,讨论了T形齿结构和梯形齿结构慢波系统几何尺寸对工作性能的影响。通过圆极化行波的高频横向电场调制电子束,导致电子束在空间的扭转,使得电子在放大过程中没有经过纵向群聚而处于减速场中,消除了非线性效应,提高了行波管的输出性能。     

Nonlinear elastic imaging using reciprocal time reversal and third order symmetry analysis

This paper presents a nonlinear imaging method for the detection of the nonlinear signature due to impact damage in complex anisotropic solids with diffuse field conditions. The proposed technique, based on a combination of an inverse filtering approach with phase symmetry analysis and frequency modulated excitation signals, is applied to a number of waveforms containing the nonlinear impulse responses of the medium. Phase symmetry analysis was used to characterize the third order nonlinearity of the structure by exploiting its invariant properties with the phase angle of the input waveforms. Then, a "virtual" reciprocal time reversal imaging process, using only one broadcasting transducer and one receiving transducer, was used to insonify the defect taking advantage of multiple linear scattering as mode conversion and boundary reflections. The robustness of this technique was experimentally demonstrated on a damaged sandwich panel, and the nonlinear source, induced by low-velocity impact loading, was retrieved with a high level of accuracy. Its minimal processing requirements make this method a valid alternative to the traditional nonlinear elastic wave spectroscopy techniques for materials showing either classical or non-classical nonlinear behavior.     

周期量级飞秒脉冲电场在非线性克尔介质中的传输

采用时间转换法研究了周期量级飞秒脉冲电场在非线性克尔介质中的传输.由于周期量级飞秒脉冲电场的脉宽小于介质拉曼响应的特征时间,在传输过程中脉冲电场会发生剧烈的变形和分裂,并在频谱上观察到了强烈的拉曼感应频移和色散波.由于周期量级脉冲电场依赖于载波包络相位,发现在脉冲电场传输过程中,主脉冲电场和色散波电场的相位线性地依赖于初始脉冲的载波包络相位.