三方晶系的非线性磁光克尔谱及其表面磁化强度取向的效应

本文计算了三方结构不同表面和不同磁化强度取向下的χ⁽²⁾、SHG、MSHG及非线性克尔旋转角Φ_k,a⁽²⁾.结果表明,SHG和Φ_k,a⁽²⁾值非常灵敏地依赖于薄膜的表面及磁化强度的取向;三方结构的SHG、Φ_k,a⁽²⁾与fcc、bcc和hcp结构的相比有很大的差异,这表明结构对非线性磁光效应有重要的影响;当M//X、Y轴时,MSHG信号很明显,这表明可通过A值的测量来研究磁性薄膜表面的磁畴结构以及取向.     

高Q Kerr介质腔中非关联双模相干态光场与V型三能级原子相互作用系统中光场的等阶Y压缩效应

本文利用多模压缩态理论,详细研究了高Q Kerr介质腔中非关联双模相干态光场与V型三能级原子相互作用系统中双模光场的一次和二次等阶Y压缩效应,结果表明:1)等阶Y压缩特性强烈地依赖于Kerr介质的三阶非线性极化系数(x)和双模光场中各模的平均光子数n¹、n²;当x<1,n¹=n²<1时,不产生等阶Y压缩效应;而当x=2.5、5、10以及n¹=n²=2、5时,光场可呈现出强烈的一次及二次等阶Y压缩效应;2)在x以及n¹、n²相同的条件下,不同压缩阶次的等阶Y压缩效应的时间演化曲线的压缩周期与压缩阶次成反比,压缩度的幅度则随压缩阶数的升高而迅速下降;3)在平均光子不变(即n¹=n²恒定),但Kerr介质不同(即x变化)的条件下,相同压缩阶数的等阶Y压缩效应的Y压缩度曲线的时间演化周期与Kerr介质的三阶非线性化系数x成反比,压缩度的幅度则随Kerr介质的三阶非线性极化系数x的增大而增强;4)等阶Y压缩效应的持续时间以及等阶Y压缩度的大小等强烈地依赖于Kerr介质的非线性程度和光场强度;一般而言,Kerr介质的非线性程度越高(即x越大),并且光场越强(即n¹=n²取值越大),等阶Y压缩效应持续时间就越短,等阶Y压缩度就越大.     

第Ⅱ种强度不等的非对称两态叠加多模叠加态光场的偶数阶等阶N次方Y压缩

本文构造了由多模复共轭相干态的相反态|{-Z_j^(a)*}>_q与多模虚共轭相干态的相反态|{-iZ_j^(b)*}>_q这两者的线性叠加所组成的第Ⅱ种强度不等的非对称两态叠加多模叠加态光场|Ψ_Ⅱ^(ab)>_q,利用多模压缩态理论研究了态|Ψ_Ⅱ^(ab)>_q的任意偶数阶等阶N次方Y压缩特性.结果发现:1)在压缩阶数N取偶数,即N=2p的条件下,无论p=2m(m=1,2,3,…,…),还是p=2m+1(m=0,1,2,3,…,…),只要构成态|Ψ_Ⅱ^(ab)>_q的两个不同的量子光场态中各对应模的强度(即平均光子数)和初始相位都不相等,亦即R_j^(a)≠R_j^(b)和φ_j^(a)≠φ_j^(b)(j=1,2,3,…,q),并且 ,则当满足一定的量子化条件(或者在一些闭区间内连续取值)时,态|Ψ_Ⅱ^(ab)>_q总可呈现出周期性变化的、任意偶数阶的等阶N次方Y压缩效应.2)在N=2p且p=2m+1(m=0,1,2,3,…,…)的条件下,若R_j^(a)=R_j^(b)和φ_j^(a)=φ_j^(b)(j=1,2,3,…,q),态|Ψ_Ⅱ^(ab)>_q则可呈现出等阶N次方Y压缩简并现象.     

一种新型的多模虚偶相干态光场的等阶N次方Y压缩与等阶N次方H压缩

本文利用新近建立的多模压缩态理论,详细研究了一种新型的多模虚偶相干态光场|Ψ_i,e⁽²⁾>_q的广义非线性等阶N次方Y压缩与等阶N次方H压缩特性.结果发现:1)态|Ψ_i,e⁽²⁾>_q是一种典型的多模非经典光场,当压缩阶数N为奇数时,态|Ψ_i,e⁽²⁾>_q在一定条件下总可呈现出周期性变化的、任意阶的等阶N次方Y压缩效应;当腔模总数q与压缩阶数N这两者的乘积q·N为奇数时,则在一定条件下态|Ψ_i,e⁽²⁾>_q又可呈现出周期性变化的、任意阶的等阶N次方H压缩效应.2)态|Ψ_i,e⁽²⁾>_q的等阶N次方Y压缩与等阶N次方H压缩效应这两者的压缩程度和压缩深度分别与几率幅γ_q^(e)、压缩参数R_j、各模的初始相位φ_j(或者各模的初始相位和 φ_j)、压缩阶数N以及腔模(指纵模)总数q等呈较强的非线性关联,等阶N次方H压缩效应与上述诸参量之间的非线性关联程度要比等阶N次方Y压缩效应的更强.3)多模虚偶相干态光场|Ψ_i,e⁽²⁾>_q与多模偶相干态光场|Ψ_,e>_q及多模复共轭偶相干态光场|Ψ*_,e⁽²⁾>_q这后两者的等阶N次方Y压缩效应和等阶N次方H压缩效应的压缩条件和压缩特性正好相反,这种现象就称为相反压缩.     

第Ⅱ种强度不等的两态叠加多模叠加态光场的等阶N次方H压缩1腔模总数与压缩阶数两者之积取偶数的情形

利用多模压缩态理论研究了第种强度不等的非对称两态叠加多模叠加态光场|Ψ_Ⅱ^(ab)〉q的等阶N次方H压缩特性.结果发现:1)当腔模总数q与压缩阶数N的乘积取偶数,亦即qN=2p时,无论p=2m(m=1,2,3,…,…),还是p=2m+1(m=0,1,2,3,…,…),只要各模的初始相位差(φ_j^(a)-φ_j^(b))、态间的初始相位差(θ_nq^(aR)-θ_nq^(bR))及光子干涉项的幅度 1R_j^(a)R_j^(b)等分别满足一定的条件,则态|Ψ_||^(ab)〉q的第一和第二正交分量总可分别呈现出周期性变化的等阶N次方H压缩效应.2)当qN=2p且p=2m+1(m=0,1,2,3,…,…)时,若构成态|Ψ_Ⅱ^(ab)〉q的两个不同的量子光场态中各对应模的强度(即平均光子数)和初始相位相等,亦即R_j^(a)=R_j^(b)和φ_j^(a)=φ_j^(b)(j=1,2,3,…,q),则态|Ψ_Ⅱ^(ab)〉q可呈现出“等阶N次方H压缩简并”现象.     

第Ⅱ类三态叠加多模叠加态光场等幂次2m+1次方Y压缩

构造了由多模虚相干态|{iZ_j}>_q、多模虚相干态的相反态|{-iZ_j}>_q和多模真空态|{O_j}>_q这三种不同的量子光场态的线性叠加所组成的第Ⅱ类三态叠加多模叠加态光场|ψ₂⁽³⁾>_q.利用多模压缩态理论,研究了态|ψ₂⁽³⁾>_q的广义非线性等幂次2m+1次方Y压缩特性.结果发现:在压缩次数N=2m+1(m=0,1,2,3,…,…)的条件下,只要各模的初始相位和态间的初始相位差分别满足一定的取值条件,态|ψ₂⁽³⁾>_q就可呈现出周期性变化的、任意奇数次的广义非线性等幂次N次方Y压缩效应.     

光学微腔中少光子数叠加态的耗散动力学

通过考察耗散光学腔中少光子数叠加态的Wigner函数随时间 的变化行为, 揭示其非经典特性的动力学演化. 结果表明, 初始时Wigner函数为负的少光子数叠加态, 在耗散过程中其负性逐渐减小 直至消失, 并最后达到一个稳定的正值. 但这并不意味着耗散量子态非经典特性的完全消失. 实际上, 作为非经典特性的另一个重要参量, 光子的二阶关联函数g⁽²⁾(0) (g⁽²⁾(0)<1意味着光子是非经典地反聚束) 是一个耗散动力学不变的物理量. 我们证明, 光子的二阶反关联函数g^(2A)(0)却是一个随着耗散而改变的物理参量, 从而可以用于描述光学微腔中光量子态的耗散动力学行为. 最后, 我们给出一个在实验上如何制备少光子数叠加态并对其Wigner函数进行探测的方案.     

第V类两态叠加多模叠加态光场的广义非线性等阶N次方Y压缩

本文构造了由多模真空态|{0_j}>_q和多模虚相干态的相反态|{-iZ_j}>_q这两者的线性叠加所组成的第V类两态叠加多模叠加态光场|ψ₅⁽²⁾>_q.利用多模压缩态理论,研究了态|ψ₅⁽²⁾>_q的广义非线性等阶N次方Y压缩特性.结果发现:1)态|ψ₅⁽²⁾>_q是一种典型的多模非经典光场;无论压缩阶数N取奇还是取偶,只要各模的初始相位φ_j(j=1,2,3,…,…,q)和态间的初始相位差(θ_nq^(I)-θ_oq^(o))等满足一定的取值条件,态|ψ₅⁽²⁾>_q总可呈现出周期性变化的、任意奇数阶和任意偶数阶的广义非线性等阶N次方Y压缩效应.2)态|ψ₅⁽²⁾>_q所分别呈现的任意奇数阶和任意偶数阶的等阶N次方Y压缩效应,其压缩条件、压缩特征以及压缩程度和压缩深度等各不相同.3)无论压缩阶数N取奇还是取偶,态|ψ₅⁽²⁾>_q的第一和第二这两个正交分量的等阶N次方Y压缩效应总是呈现出周期性的互补关系.     

第Ⅰ类两态叠加多模叠加态光场的非线性高阶压缩特性研究

本文在文献20的基础上进一步提出了多模辐射场的N-Y最小测不准态、N-H最小测不准态、N-Y压缩最小测不准态以及N-H压缩最小测不准态等的定义.构造了由多模(q模)相干态|{Z_j}>_q及其相反态|{-Z_j}>_q的线性叠加所组成的第Ⅰ类两态叠加多模叠加态光场|ψ₁⁽²⁾>_q,利用文献20新近提出的有关多模辐射场的两种非线性高阶压缩的定义,首次对态|ψ₁⁽²⁾>_q的N次方Y压缩及N次方H压缩效应进行了详细研究.结果表明,1)当N为偶数时,态|ψ₁⁽²⁾>_q恒处于N-Y最小测不准态;当N为奇数时,态|ψ₁⁽²⁾>_q在一定条件下可呈现出周期性变化的、任意阶的N次方Y压缩效应.2)当q·N为偶数时,态|ψ₁⁽²⁾>_q恒处于N-H最小测不准态;当q·N为奇数时,在另外的条件下,态|ψ₁⁽²⁾>_q则可呈现出周期性变化的、任意阶的N次方H压缩效应.3)N次方Y压缩及N次方H压缩效应的压缩深度与腔模总数q、压缩参数R_j以及压缩阶数N等非线性相关,后者与上述参量的非线性关联程度要比前者的更强.     

第Ⅵ类两态叠加多模叠加态光场的等阶N次方Y压缩特性研究

本文构造了由多模相干态|{Z_j}〉q与多模虚相干态|{iZ_j}〉q这两者的线性叠加所组成的第Ⅵ类两态叠加多模叠加态光场|Ψ₆⁽²⁾〉q.利用多模压缩态理论,研究了态|Ψ₆⁽²⁾〉q的广义非线性等阶N次方Y压缩特性.结果发现:1)在压缩阶数N＝2p且p＝2l(l＝1,2,3,…,…)的条件下,无论各模的初始相位φ_j(j＝1,2,3,…,q)、态间的初始相位差(θ_pq^(R)-θ_pq^(I))以及各单相干态光场的平均光子数之和 R_j²等如何变化,态|ψ₆⁽²⁾〉q总是恒处于偶数阶等阶N-Y最小测不准态.2)在压缩阶数N＝2p且p＝2l+1(l＝0,1,2,3,…,…)的条件下,当各模的初始相位φj、态间的初始相位差(θ_pq^(R)-θ_pq^(I))以及各单模相干态光场的平均光子数之和 R_j²等分别满足一定的量子化条件(或者在特定的区间内连续取值)时,态|ψ₆⁽²⁾〉q的第一及第二这两个正交分量总可分别呈现出周期性变化的偶数阶的等阶N次方Y压缩效应.     

石英玻璃的电致二阶非线性极化及其热擦除性

本文报导了石英玻璃的电致二阶非线性极化及其热擦除性的实验研究结果。通过电致二次谐波测量发现:在一定的电场极化条件下,石英玻璃的电致二阶非线性极化强度随极化时间的延长而逐渐增强,并渐趋饱和;石英玻璃的电致二阶非线性极化可通过热处理而擦除,并随热擦除时间的延长呈动态衰减趋势。根据玻璃的电致二阶非线性极化的“偶极子取向”模型,对实验结果进行了讨论.     

横向塞曼激光器中非线性混频效应的理论

本文应用Lamb半经典理论,采用矢量场模型,研究了横向Zeeman激光介质的高阶非线性效应,计算了该情况下横向Zeeman激光介质的三阶极化强度和光强的解析表达式,从理论上解释了σ与π光差拍畸变以及σ与π光本身的高次谐波现象,给出了发生畸变的物理原因。 关键词：     

飞秒激光在晶体中传输的级联非线性过程

系统地回顾了有关级联过程导致的各种非线性效应的工作,指出了级联效应可导致不同光谱成分间出现能量转移现象,且二阶级联过程中产生的白光还能够提供种子光进而得到基于参量放大过程的宽带锥形辐射。在此基础上,进一步研究了入射的基频波长对于超连续白光能量转移效果及产生倍频效率的影响以及二阶级联过程引起的偏振调制现象,指出当入射波长越靠近相位匹配波长时倍频效率越高,发现二阶级联效应还可以引起显著的基频光偏振调制。     

全内反射构型下分子在十六烷-水界面取向角度的二次谐波测量

测量了在全内反射条件及非全内反射条件下,两种探针分子在十六烷-水界面上的取向角度.通过详细的偏振分析,发现探针分子在两种构型下的取向角度测量结果一致.表明全内反射条件下,取向角度的测量和偏振分析同样是准确且可行的.     

Variational method for the nonlinear dynamics of an elliptic magnetic stagnation line

The nonlinear evolution of the kink instability of a plasma with an elliptic magnetic stagnation line is studied by means of an amplitude expansion of the ideal magnetohydrodynamic equations. Wahlberg et al. [12] have shown that, near marginal stability, the nonlinear evolution of the stability can be described in terms of a two-dimensional potential U(X,Y), where X and Y represent the amplitudes of the perturbations with positive and negative helical polarization. The potential U(X,Y) is found to be nonlinearly stabilizing for all values of the polarization. In our paper a Lagrangian and an invariant variational principle for two coupled nonlinear ordinal differential equations describing the nonlinear evolution of the stagnation line instability with arbitrary polarization are given. Using a trial function in a rectangular box we find the functional integral. The general case for the two box potential can be obtained on the basis of a different ansatz where we approximate the Jost function by polynomials of order n instead of a piecewise linear function. An example for the second order is given to illustrate the general case. Some considerations concerning solar filaments and filament bands (circular or straight) are indicated as possible applications besides laboratory experiments with cusp geometry corresponding to quadripolar cusp geometries for some clouds and thunderstorms.     

Simulation of the Second Grade Fluid Model for Blood Flow through a Tapered Artery with a Stenosis

We analyze the blood flow through a tapered artery, assuming the blood to be a second order fluid model. The resulting nonlinear implicit system of partial differential equations is solved by the perturbation method. The expressions for shear stress, velocity, flow rate, wall shear stress and longitudinal impedance are obtained. The physical behavior of different parameters is also discussed, as are trapping phenomena.     

Barnett kinetic coefficients in dense charged and neutral media

An approach based on the nonlinear response theory is proposed for determining nonlinear transport properties of nonideal multielement charged and neutral media. A version of this theory developed for describing these properties involves the comparison of phenomenological conservation equations for dense media in the Barnett approximation and microscopic equations for operators of dynamic variables. The Mori algorithm used for formulating the microscopic equations makes it possible to obtain these equations for non-ideal media in the form of generalized nonlinear Langevin equations. As a result, macroscopic expressions are derived for nonlinear kinetic coefficients in the second order in thermal perturbations (of temperature, mass velocity, etc.). The expressions for nonlinear and linearized Barnett kinetic coefficients are compared.     

Intrinsic optical bistability in Kerr ferroelectric materials

In this paper we investigate the intrinsic optical bistability (IOB) in a ferroelectric (FE) single layer using an alternative analysis. The FE material is considered to have an intensity-dependent refractive index where the third order nonlinear susceptibility χ⁽³⁾ acts like Kerr coefficient. The nonlinear response of the FE medium is modeled using the Landau-Khalatnikov (LK) dynamical equation with the nonlinear anharmonic potential obtained from the Landau-Devonshire free energy expressed in terms of polarization. Within a single frequency approximation, the electromagnetic wave equation is written in terms of the polarization P rather than the electric field E as the dependent variable. With the application of the nonlinear boundary conditions we have derived expressions for both reflectance and transmittance as a function of the electric field incident amplitude, polarization and other material parameters. The formalism proves to be more suitable for FE materials since most of these materials have highly linear and nonlinear coefficients especially when the operating frequency is in the resonance region. The effects of thickness, operating frequency and temperature on BaTiO₃ single film are investigated theoretically. The results presented here agree in principle with the recent experimental observations of intrinsic OB in BaTiO₃ monocrystal and other FE photorefractive materials.     

微量子腔结边电荷极化结构中的线性和二阶非线性动态电导性质的研究

采用有效哈密顿量和有相互作用的分立势模型，利用格林函数和耦合参量得出了量子点(腔)在有结边电荷积累极化时的线性和二阶非线性交流电导虚部(emittance)的明确表达式.发现在经典情况下，电导虚部和电化学电容都等于经典的几何电容.在非经典情况下，如果发生全反射，电导虚部和电化学电容相等，但两者皆不等于经典的几何电容.在有隧穿的情况下，电导虚部和电化学电容以及经典电容三者都不相等.该结果对于量子器件中的电容测量具有指导作用. 关键词： 格林函数 交流电导 电化学电容     

Kinetic Theory of a Weakly‐Nonideal Spatially Nonuniform Polarizable Plasma

A nonmarkovian and nonlocal kinetic equation, which is a generalization of the (nonlinear) Balescu‐Lenard equation, is derived for a weakly nonuniform multicomponent polarizable plasma. A specific expansion of the plasma resolvent, which allow to separate the dymamic, kinetic and hydrodynamic scales, is proposed. Explicit expressions of the collision integral and of the nonequilibrium pair correlation function are given in an approximation which take into account the effect of patial and temporal nonlocality a well as of the polarization. Balance equation for the momentum and energy densitie are calculated in the first order in nonlocality, and potential contributions to the fluxes due to polarization are obtained.