Malus’ law for X-ray radiation

Light propagation through a polarizer-analyzer system is investigated on the basis of quantum concepts about the nature of light. It is shown that Malus’ law, which is based on principles of classical electrodynamics, does not fully take into account all effects that can arise under light propagation through a polarizer-analyzer system. In particular, the phenomenon of a possible change in the light frequency is not considered, e.g., in the case of X-ray radiation. The derivation of Malus’ law based on quantum principles is presented. For comparison, the differential effective cross section of the interaction between a photon and an electron is found taking into account rotation of the photon polarization plane in the Compton effect.     

光子的态矢量函数

从广义Schr?dinger方程出发，在三个充分必要的量子化条件规范下，得到了一个新颖的光子一维态矢量函数，除了光子的能量和动量特征以外，它还包含有光子的角动量属性，完整地描述了光子作为量子力学中相对论自由粒子的行为.对一维光子态矢量函数的分析不仅定义了描述光子行为的微观参量——概率幅和相位，而且将这些微观参量与光束的宏观偏振联系了起来，具体剖析了一个人们一直感到困惑的偏振问题，得到了圆满的解释. 关键词： 光子态矢量函数 概率幅 相位 偏振     

光在Metasurface中的自旋-轨道相互作用

探讨了光在Metasurface中的自旋-轨道相互作用, 理论分析了Metasurface 对圆偏振和线偏振光的转换. 结果表明: 光与具有空间非均匀性和各向异性性的Metasurface的相互作用导致了自旋-轨道角动量的耦合. 采用Metasurface与螺旋相位片组合在一起进行了验证实验, 所得实验结果与理论分析完全一致. 这些结论有助于我们更加深入理解Metasurface 对光的操控.     

基于周期极化晶体MgO:PPLN的纠缠光子对制备过程的研究

基于二阶非线性效应的自发参量转换技术制备纠缠光子对过程中,以掺5 mol%MgO:PPLN周期极化晶体为研究对象,将光参量变换过程中的动量守恒和能量守恒条件与该晶体的色散方程,以及晶体极化周期随温度变化的热膨胀方程相联系,得到了355 nm、405 nm、532 nm、780 nm和1 064 nm这5个实验室常用波长点在制备纠缠光子对时的周期调谐特性和温度调谐特性。研究过程中发现,出现了晶体极化周期过小和产生两对纠缠光子对问题,总结并归纳了各波长点在一定极化周期和温度下与非线性晶体作用所产生的纠缠光波段范围。当选用其他非线性周期极化晶体进行实验时,改变QPM动量守恒条件中的极化周期项,同时根据具体使用的晶体改变色散方程。该研究方案可直接推广到使用不同非线性晶体产生通信光波段或红外光波段的纠缠光子对研究中,在制备量子光源等领域具有重要研究价值。     

Degree of polarization for single-photon beam in a turbulent atmosphere

The polarization fluctuations of single-photon beam propagation through the slant path turbulent atmosphere are studied. The Stokes operators and the degree of polarization of single-photon beam in a turbulent atmosphere are obtained. It is shown by analytical calculations, that the quantum degree of polarization of linearly polarization light is a decrease function of the atmospheric turbulence strength and the propagation distance for lower detection photon number.     

相对论涡旋高次谐波的产生与调控理论研究

目前,具有螺旋相位波前和环状光强分布的涡旋光束已在光学领域获得了广泛应用,其产生与调控自然成了研究的热点。利用三维粒子模拟程序对双色拉盖尔高斯激光驱动固体等离子激发同时携带自旋角动量与轨道角动量的高次谐波的物理过程进行了研究,根据高次谐波产生过程中的光子能量与角动量守恒定律对其内在物理机制进行了理论分析,并讨论了对谐波阶次、偏振态（自旋角动量）以及拓扑荷数（轨道角动量）进行调控的方法。研究结果为开发高亮度、超短超快、短波长、自旋与轨道角动量可调控的涡旋光束辐射源提供了理论依据,在光学微操控、超分辨成像、光通信以及离子加速等领域具有较大的实际应用前景。     

声子角动量与手性声子

在经典的物理学理论中,声子广泛地被认为是线极化的、不具有角动量的.最近的理论研究发现,在具有自旋声子相互作用的磁性体系(时间反演对称性破缺)中,声子可以携带非零的角动量,在零温时声子除了具有零点能以外还带有零点角动量;非零的声子角动量将会修正通过爱因斯坦-德哈斯效应测量的回磁比.在非磁性材料中,总的声子角动量为零,但是在空间反演对称性破缺的六角晶格体系中,其倒格子空间的高对称点上声子具有角动量,并具有确定的手性;三重旋转对称操作给予声子量子化的赝角动量,赝角动量的守恒将决定电子谷间散射的选择定则;此外还理论预测了谷声子霍尔效应.     

柱矢量光束的角动量性质

介绍了非近轴光束的表示理论,利用该表示理论很好地解决了非近轴光束的角动量问题,发现非近轴光束的总角动量可以严格地分解成自旋和轨道两部分,但是两者都依赖于由偏振椭圆度表征的光束的偏振状态。主要研究了柱矢量光束的角动量问题。给出了动量空间和位形空间中的柱矢量光束表达式和角动量算符表达式。通过分析两个空间中的角动量算符及柱矢量光束表达式,发现在这两种空间中,具有螺旋型相位的柱矢量光束是角动量算符沿着传播方向的分量的本征态,其本征值与偏振椭圆度无关,这为计算这类特殊光束的角动量提供了一种新方法。     

Photon polarization as a probe for quark–gluon plasma dynamics

Prospects of measuring polarized photons emitted from a quark–gluon plasma (QGP) are discussed. In particular, the detection of a possible quark spin polarization in a QGP using circularly polarized photons emitted from the plasma is studied. Photons leave the QGP without further interaction and thus provide a primary probe for quark polarization within the QGP. We find that photon polarization cannot solely arise due to a possible QGP momentum space anisotropy, but may be enhanced due to it. In particular, for oblate momentum distributions and high photon energies, quark polarization is efficiently transfered to photon polarization. The role of competing sources of polarized photons in heavy-ion collisions is discussed.     

Study of the photon’s pole structure in the noncommutative Schwinger model

The photon magnetic moment for radiation propagating in magnetized vacuum is defined as a pseudotensor quantity, proportional to the external electromagnetic field tensor. After expanding the eigenvalues of the polarization operator in powers of \(k^2\) , we obtain approximate dispersion equations (cubic in \(k^2\) ), and analytic solutions for the photon magnetic moment, valid for low momentum and/or large magnetic field. The paramagnetic photon experiences a redshift, with opposite sign to the gravitational one, which differs for parallel and perpendicular polarizations. It is due to the drain of photon transverse momentum and energy by the external field. By defining an effective transverse momentum, the constancy of the speed of light orthogonal to the field is guaranteed. We conclude that the propagation of the photon non-parallel to the magnetic direction behaves as if there is a quantum compression of the vacuum or a warp of space-time in an amount depending on its angle with regard to the field.     

非线性克尔效应对飞秒激光偏振的超快调制

研究了近红外飞秒激光的偏振在太赫兹频率的超快调制.利用抽运-探测光谱技术,通过改变两个脉冲之间的延迟时间可以控制光脉冲的旋转角.在Li：NaTb（WO₄）₂磁光晶体中观察到探测光的偏振随延迟时间变化的高速振荡,振荡信号的中心频率为0.19 THz.这种超快偏振调制现象可以解释为,抽运-探测实验构置中,前向传播的抽运光诱导的光学克尔非线性引起被晶体远端表面所反射的背向传播的探测光脉冲偏振面的额外旋转.通过改变抽运光的圆偏振旋性可以控制探测光调制信号的相位和振幅.实验结果表明,非线性光学克尔效应可以作为一种全新的手段,在磁光晶体中实现近红外飞秒激光以太赫兹频率的超快偏振调控.这将在超快磁光调制器等全光器件中得以应用.实验结果将有助于偏振依赖的超快动力学过程的研究.     

Another proof that the future can influence the present

A modified Young double-slit experiment proposed by Wootters and Zurek is considered in which a system P of parallel plates covered with a photographic emulsion has been set up in the region where we would normally expect the central interference fringes. Because under certain conditions P makes it possible to conclude with much more than50% certainty through which of the two slits each particular photon passed, the relevant interference pattern becomes blurred. It is proved that this implies a retroactive effect because the setup of P and the interaction of photons with P appear to influence the momentum transferred to the photons by the edges of the slits at an earlier stage of the experiment.     

Changes of polarization of light beams on propagation through tissue

The values of the degree of polarization and the coherence of the light beam are of great importance in many areas. In this paper, we study the effects of tissue turbulence on the degree of polarization of a partially coherent electromagnetic beam. Based on the unified theory of coherence and polarization for random electromagnetic beams and the spectral density of the index of refraction fluctuations of tissue, we have established the detailed formula for calculating the change of the degree of polarization of the beam when propagating through tissue. Compared with the light propagation through atmosphere, the result shows that although the propagation distance in tissue imaging is very short, the degree of polarization of the beam may change greatly. An example was given which clearly shows the effect of the correction properties and the tissue turbulence on the degree of polarization of the light beam propagating within the tissue.     

光脉冲在含玻色元激发的非线性介质中的传播与面积定理

研究了取决于场与玻色（ｂｏｓｏｎ元激发瞬间相互作用的光信号传播问题。导出了相应的‘面积定理’，是将只关系到光脉冲在二能级系统中传播的面积定理的一种推广。所得结果和用光与玻色物质耦合模型对增强吸收型光双稳的解决是一致的。     

Photon Recoil in Light Scattering by a Bose–Einstein Condensate of a Dilute Gas

Photon recoil upon light scattering by a Bose–Einstein condensate (BEC) of a dilute atomic gas is analyzed theoretically accounting for a weak interatomic interaction. Our approach is based on the Gross–Pitaevskii equation for the condensate, which is coupled to the Maxwell equation for the field. The dispersion relations of recoil energy and momentum are calculated, and the effect of weak nonideality of the condensate on the photon recoil is ubraveled. A good agreement between the theory and experiment [7] on the measurement of the photon recoil momentum in a dispersive medium is demonstrated.     

Probing vacuum birefringence by phase-contrast Fourier imaging under fields of high-intensity lasers

In vacuum high-intensity lasers can cause photon–photon interaction via the process of virtual vacuum polarization which may be measured by the phase velocity shift of photons across intense fields. In the optical frequency domain, the photon–photon interaction is polarization-mediated described by the Euler–Heisenberg effective action. This theory predicts the vacuum birefringence or polarization dependence of the phase velocity shift arising from nonlinear properties in quantum electrodynamics (QED). We suggest a method to measure the vacuum birefringence under intense optical laser fields based on the absolute phase velocity shift by phase-contrast Fourier imaging. The method may serve for observing effects even beyond the QED vacuum polarization.     

Fundamental quantum limit to the multiphoton absorption rate for monochromatic light

The local multiphoton absorption rate for an arbitrary quantum state of monochromatic light, taking into account the photon number, momentum, and polarization degrees of freedom, is shown to have an upper bound that can be reached by coherent fields. This surprising result rules out any quantum enhancement of the multiphoton absorption rate by momentum entanglement.     

Electromagnetic momentum in frontiers of modern physics

We review the role of the momentum of the electromagnetic (EM) fields P_e in several areas of modern physics. P_e represents the EM interaction in equations for matter and t waves propagation. As an application of wave propagation properties, a first order optical experiment which tests the speed of light in moving rarefied gases is presented. Within a classical context, the momentum P_e appears also in proposed tests of EM interactions involving open currents and angular momentum conservation laws.Moreover, P_e is the link to the unitary vision of the quantum effects of the Aharonov-Bohm (AB) type and, for several of these effects, the strength of P_e is evaluated. These effects provide a quantum approach to evaluate the limit of the photon mass m_ph. A new effect of the AB type, together with the scalar AB effect, provides the basis for table-top experiments which yield the limit m_ph = 9.4 × 10^-52 g, a value that improves the results achieved with recent classical and quantum approaches.     

Propagation of radially polarized beams in the oceanic turbulence

Based on the extended Huygens–Fresnel principle and the unified theory of coherence and polarization of light, we investigate the propagation properties of a radially polarized beam through turbulent ocean. Analytic formulae for the spectral density, the spectral degree of polarization, and the beam characteristics of such a beam on propagation are discussed. It is shown that under the influence of oceanic turbulence, the radially polarized beam will change to a partially polarized one and the beam profile will approach to a Gaussian distribution.     

高能重离子非对心碰撞中的整体夸克极化

There exists a large local relative orbital angular momentum between produced partons along the direction opposite to the reaction plane in the early stage of non-central heavy-ion collisions. This initial local orbital angular momentum can lead to quark polarization along the same direction due to spin-orbital coupling in QCD. We present the quark polarization by using hard thermal loop gluon propagator for quark-quark scattering in quark-gluon plasma and compare it with the result obtained from the static potential model.