等离子体/色散吸收介质界面系统中光场量子起伏功率谱

利用格林函数方法量子化色散吸收介质中的电磁场,研究了等离子体/色散吸收介质系统光场的量子性质.理论和数值计算表明,系统的工作状态与所选光场频率密切相关,等离子体介质的阻尼性明显地影响自身区域电场量子起伏功率谱,并且对另一侧介质中电场量子起伏功率谱的变化有连带作用.     

基于马赫-曾德干涉法测量原子介质的色散特性

理论分析了利用马赫-曾德干涉仪及平衡零拍探测技术测量相干介质色散特性的方法,实验测量了三能级铯原子分别在电磁诱导透明和电磁诱导吸收两种截然相反的相干效应下的色散特性.研究表明:在原子频率共振中心,对于透明介质,由于吸收减弱效应,信号光能穿出介质,保证了有效色散信息,即正常色散特性能被测量到;相反地,对于吸收介质,由于强吸收效应,只有在低粒子数密度条件下,即保证有信号光没有被完全吸收而穿出介质,才能测量到介质的反常色散特性;当提高铯泡温度时,介质对信号光吸收增强以至完全吸收,并且吸收频谱宽度变宽,导致色散信息不能被有效测量到.     

含色散介质的一维光子晶体微腔的透射谱

研究了含色散介质的一维光子晶体微腔的透射谱,对色散介质采用Lorentz振子模型,腔模的频率设置在光子晶体带隙中心。发现当吸收可以忽略时,色散效应将导致在腔模附近有很高的态密度,与此相应地在透射谱中出现一个较宽的透射带。当吸收存在时透射带中心的透射峰消失,但带尾的透射峰依然存在。     

非对称半导体量子阱中自发辐射相干诱导透明

研究了一束低强度探测脉冲光场在一个非对称半导体量子阱中的传输特性.在相同参数条件下,通过由自发辐射相干产生的交叉耦合系数来调控介质对探测场吸收、色散的变化规律.结果表明:从自发辐射相干的引入到达到相干最大,介质的吸收不断减小,同时强色散也随之进入透明窗口.     

一维对称光子晶体的简正耦合模

对一维对称光子晶体中的色散介质采用洛仑兹振子模型,通过考虑色散介质层两侧的边界条件,得到了表征色散介质层的转移矩阵.对线性层及色散δ层均采用传输矩阵的方法,研究了一维含色散介质的光子晶体微腔中的简正耦合模.由于光与色散介质的相互作用,纵腔模将分裂成简正耦合模.通过改变色散介质的相关参数,详细研究了简正耦合模频率的移动、均匀展宽效应和失谐效应.发现两个简正的耦合模的频率间距主要依赖于振子的耦合强度,与约化的振子的HWHM线宽无关.失谐效应则会使其中的一个峰降低,而另一个峰相对拉高,这一现象可以通过Fabry-Pérot腔得到很好的解释.     

负折射率材料对Casimir效应的影响

研究了负折射率材料介质板间的Casimir效应.对于负折射率材料中由Drude-Lorentz型色散关系描述的介电常数和磁导率，色散曲线中负值频带的曲线结构由各色散吸收参数所决定，色散曲线负值频带宽度和负区域的深度等性质的变化影响了介质材料板的反射特性，进而对两材料板间的Casimir效应强弱起着重要的作用.     

色散吸收非对称介质光腔系统中光场量子起伏的功率谱

借助系统格林函数和色散吸收介质中电磁场量子化过程,通过数值计算研究非对称色散吸收介质光腔系统中光场量子起伏的功率谱.结果表明,介质的折射和吸收性质分别对真空场起伏功率谱的振荡频率、振幅产生影响,腔两侧介质折射系数的对称性能更有效地抑制腔外空间场起伏功率谱的振荡;介质折射系数愈大,则其中光场起伏功率谱振荡中心愈低、振荡频率愈大,与此同时,光腔内真空场起伏功率谱振荡幅度加大.     

浅谈平面振子的阻尼运动

从动力学方程出发并结合Mathcad数值计算,研究了平面振子的阻尼运动,并分析了阻尼系数对平面振子运动轨迹的影响.     

含色散介质的一维光子晶体微腔中简正耦合模的物理图像

对一维光子晶体中的色散介质采用洛伦兹振子模型,对线性层及色散δ层均采用传输矩阵的方法,研究了一维含色散介质的光子晶体微腔中的简正耦合模.通过改变洛伦兹振子和微腔之间的失谐频率,分析了简正耦合模频率的变化情况.在失谐频率比较大时,光与洛仑兹振子间的耦合作用较小,简正耦合模中的一个接近腔模频率,而另一个则接近洛仑兹振子的共振频率;在失谐频率比较小时,光与洛仑兹振子间的耦合作用较大,简正耦合模与未耦合的腔模频率和洛仑兹振子的共振频率之间的差别较为明显.最后通过引进该结构的复有效折射率,对含色散介质的系统,由于带隙中间的共振模被湮灭并分裂为左右两个耦合模,其复有效折射率虚部在原共振峰处跃变为一较大值,而在新生成的两个耦合模附近趋近于零,光与色散介质相互耦合而形成的腔极化激元的物理图像十分清晰.     

声子色散对量子点中磁极化子性质的影响:压缩态变分法

采用基于逐次正则变换的变分方法研究了利用单模压缩态变换处理双线性项的情况下声子色散对抛物量子点中磁极化子性质的影响。首先,应用位移振子形式的幺正变换来对角化相关的哈密顿量,然后采用压缩态变换来处理在第一次幺正变换中产生的双线性项。计算了在声子色散影响下磁极化子的基态能量及电子周围平均声子数。讨论了在弱耦合情况下,受限长度、回旋频率、电子-声子耦合常数、色散系数分别与基态能量和平均声子数之间的依赖关系。我们可以得到基态能量随受限长度的减小和回旋频率的增加而迅速增大,随着色散系数的增大而降低,平均声子数随着色散系数的增大而减小。     

基于Tracker软件研究竖直方向阻尼振动的居家实验

设计了基于Tracker软件研究竖直方向阻尼振动的居家实验.选用橡皮筋和水果自制振子模型,利用Tracker软件对自制橡皮筋振子的阻尼振动进行研究,绘制橡皮筋振子模型在竖直方向上做阻尼振动的“y t”图像,并通过数据拟合,计算出该阻尼振动的振幅、周期、圆频率、阻尼系数等,是利用生活物品进行大学物理实验的一次尝试.     

The optical properties of a V-type atomic medium driven by an additional field

The effects of an additional level and field on the dispersion and absorption characteristics of a four-level atomic medium based on a V-type are studied. The steady state solutions are given under two different fourth level damping rate relations, with the tunable weak probing field and resonant coupling and driving fields.     

近垂直传播电子回旋寻常波的传播和吸收特性的解析研究

对近垂直入射的电子回旋寻常波的传播和吸收，用相对论等离子体色散关系进行了分区分析，获得了共振层附近内区O－模与X－模的耦合的准确表达式，该结果与非相对论近似下的结论有重大差别，获得了波衰减因子的解析表达式，波的衰减因子由两部分组成：O－模的相对论衰减及与O－模耦的X－模的衰减。     

On the theory of Langmuir waves in a quantum plasma

Nonlinear quantum-mechanical equations are derived for Langmuir waves in an isotropic electron collisionless plasma. A general analysis of dispersion relations is carried out for complex spectra of Langmuir waves and van Kampen waves in a quantum plasma with an arbitrary electron momentum distribution. Quantum nonlinear collisionless Landau damping in Maxwellian and degenerate plasmas is studied. It is shown that collisionless damping of Langmuir waves (including zero sound) occurs in collisionless plasmas due to quantum correction in the Cherenkov absorption condition, which is a purely quantum effect. Solutions to the quantum dispersion equation are obtained for a degenerate plasma.     

On the Spectral Distribution of Equilibrium Radiation and Zero-Point Fluctuations in the Coulomb System

The consideration of equilibrium radiation in plasma-like media shows that the spectral energy distribution of such radiation differs from that of Planck equilibrium radiation. Based on the previously derived relation for the spectral energy density of equilibrium radiation in the system of charged particles, accounting for finite damping in a medium with spatial dispersion, the limiting case of infinitesimal damping dispersion is considered. It was shown that zero-point vacuum fluctuations being a component of the total spectral energy distribution in the medium should be renormalized when using certain models for the transverse plasma permittivity. In this case, renormalized zero-point vacuum fluctuations become dependent on plasma parameters. The possibility of the manifestation of this effect is discussed.     

Propagation of the ultrashort laser pulses through the quantum nonlinear medium with resonant properties

The propagation of ultrashort few-cycle laser pulses through a quantum nonlinear medium with resonant properties is studied using the method of slowly varying amplitudes with allowance for dispersion effects. A self-consistent system of nonlinear wave equation for the evolution of laser field and the nonstationary Schrödinger equation that determines the material polarization response is numerically solved. Specific features of the propagation of laser pulse caused by a relatively large spectral width and the nonadiabatic character of the laser pulse are established. The rise of the slowly dumping polarization at the eigenfrequency of the medium and the consequent stretching of the laser pulse are observed. The role of the resonant absorption of the laser energy in the medium is analyzed. The nonlinear spectral broadening is demonstrated for the laser pulse propagating through the medium.     

电-磁振子组合型小型化超宽带天线研究

 采用频域分析的方法，对电-磁振子组合型超宽带天线物理特性进行了研究，结果表明：天线中的电振子和磁振子在波的传输和辐射过程中起互补作用，扩展了小尺寸天线的工作频带，提高了天线的辐射效率。还给出了50cm天线的模拟和测量结果：电压驻波比小于3时，天线带宽大于10倍频程，模拟与测量结果基本吻合。     

Zur Ultrarotdispersion der Alkali-Halogenide

The infra-red spectra of LiF, NaCl and CsBr are interpreted according to the dispersion theory ofBorn andHuang1. This theory takes into account anharmonic terms in the lattice potential and leads to a frequency-dependent damping which describes the absorption. This damping function is first obtained by evaluating the empirical data of the optical constants and is then compared with an approximate computation based on the frequency spectrum of lattice vibrations. The result of this comparison shows that theory and experiment correspond qualitatively very closely, especially with respect to the secondary structure in dispersion.     

On the velocity of propagation of a frequency-modulated wave packet in a dispersive absorbing medium

It is shown that the velocity of propagation of a frequency-modulated wave packet through a strongly dispersive absorbing medium can be significantly different from (either higher or lower than) that of a non-frequency-modulated wave packet. This difference is attributed to the absorption dispersion of the medium. The easiest way to take the absorption dispersion into account is to use the formalism of the complex group velocity of a wave packet. This paper considers the propagation of a linear frequency-modulated wave packet, whose carrier frequency is close to the frequency of a spectral absorption line of the medium.     

Dissipation and dispersion properties of microinhomogeneous media

The propagation of a harmonic elastic wave in a microinhomogeneous (defect-containing) medium is considered in the framework of the rheological model that reperesents the medium in the form of a one-dimensional chain of masses connected by purely elastic elements and by Kelvin-Voigt viscoelastic elements. Analytical expressions are derived for the dissipation and dispersion characteristics of this medium for various distributions of the parameters of the viscoelastic elements. The dissipation and dispersion properties are found to obey the Kramers-Kronig relations. It is also shown that the damping decrement of the wave is almost constant, and the phase velocity monotonically increases in a sufficiently wide range of parameters of the viscoelastic elements in a wide frequency band. The derived expressions for the dispersion and dissipation are used to simulate the propagation of broadband pulses in this kind of medium.