Photoexcitation of graphene with twisted light

We study theoretically the interaction of twisted light with graphene. The light-matter interaction matrix elements between the tight-binding states of electrons in graphene are determined near the Dirac points. We examine the dynamics of the photoexcitation process by posing the equations of motion of the density matrix and working up to second order in the field. The time evolution of the angular momentum of the photoexcited electrons and their associated photocurrents are examined in order to elucidate the mechanisms of angular momentum transfer. We find that the transfer of spin and orbital angular momentum from light to the electrons is more akin here to the case of intraband than of interband transitions in semiconductors, due to the fact that the two relevant energy bands of graphene originate from the same atomic orbitals.     

Beyond the classical Rayleigh limit with twisted light

It is shown that twisted stochastic light can serve as illumination that may produce images with a resolution overcoming the Rayleigh limit by an order of magnitude. This finding is illustrated for an isoplanatic axially symmetric system with low angular aperture and twisted scalar Gaussian Schell-model illumination.     

Radiation passage through a twisted multimode light guide

In the geometrical optics approximation, it is shown that the meridional ray plane in a twisted multimode light guide is rotated through an angle given by Berry's geometrical phase. The results obtained allow the experimentally established effect of rotation of a speckle pattern for opposite helicity of the multimode lightguide to be described. All-Union Scientific Research Institute of Engineering Physics at the Russian Federal Nuclear Center. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 58–60, October, 1999.     

Orbital angular momentum exchange in the interaction of twisted light with molecules

In the interaction of molecules with light endowed with orbital angular momentum, an exchange of orbital angular momentum in an electric dipole transition occurs only between the light and the center of mass motion; i.e., internal "electronic-type" motion does not participate in any exchange of orbital angular momentum in a dipole transition. A quadrupole transition is the lowest electric multipolar process in which an exchange of orbital angular momentum can occur between the light, the internal motion, and the center of mass motion. This rules out experiments seeking to observe exchange of orbital angular momentum between light beams and the internal motion in electric dipole transitions.     

Phase measurements of a twisted nematic liquid crystal spatial light modulator with a common-path interferometer

We present a novel and high accuracy (±1°) technique for measuring the difference in phase delay between the positive and negative eigenvectors of a twisted nematic liquid crystal spatial light modulator (LCSLM) as a function of applied voltage. We show a new architecture for a common-path interferometer where we simultaneously generate both the positive and negative eigenvectors of the LCSLM. We use an electro-optic light modulator to provide a time varying phase shift between the two eigenvectors and measure the phase delay difference between the two eigenvectors. We compare the phase delay values with those obtained using a Mach–Zehnder interferometer and find good agreement.     

Ternary phase-amplitude modulation with twisted nematic liquid crystal displays for Fourier-plane light homogenization in holographic data storage

Holographic data storage applications often use liquid crystal displays as spatial light-amplitude modulators for writing data images. The hologram created in the Fourier plane is usually applied to store the information, since this plane supplies optimal data density. A well known technique for homogenizing the light distribution in the Fourier plane is the application of external random phase modulating masks. The requirement for pixel by pixel matched positioning of the phase modulating mask and the pixels of the spatial light-amplitude modulator is hard to solve in the optical systems and any positioning error leads to significant signal degradations. The article analyses the possibilities of realizing the required simultaneous amplitude and phase modulation of light with the application of a single LCD. Twisted nematic LCDs with different maximal birefringence are numerically investigated using the Jones matrix method. Elliptical incident and exit polarizations are proposed, by which ternary phase-amplitude modulation (+1,–1,0) can be realized. Test measurements are also presented that demonstrate the validity of the calculated results.     

具有不同扭距的堆叠扭绞型复合导体临界电流特性分析

根据高温超导堆叠扭绞型复合导体的结构参数,研究堆叠带材根数及扭绞节距对其临界电流特性的影响。首先阐述了堆叠扭绞型复合导体的结构特点,据此设计并制作实验样品。在77K、自场下,对采用不同根数超导带材复合而成的导体样品,分别测试其在多个扭绞节距下的临界电流。通过实验测试可得,随着扭转角度的增大,导体的临界电流不断衰减,且堆叠带材的数量越多,导体的临界节距越大。     

Scattered light measurement of the circular birefringence in a twisted single mode fiber

This paper reports the measurements of the twist induced circular birefringence in a single mode fiber by direct observation of the scattered light. The results agree well with earlier theoretical prediction. In addition, an analysis of the evolution of the polarization in a linearly birefringent twisted medium (applicable to weakly guiding single mode (fibers) is given using the coupled mode theory and Poincaré sphere representation.     

Transient effects in the electrically controlled light transmission of a twisted nematic layer

An oscillatory after-effect in the light transmission of a twisted nematic layer is often observed when the driving field is switched off. The effect is explained as being caused by fluid motion.     

Magnetic bubble domains with twisted walls

The total energy, radius and wall width of a magnetic bubble with a cylindrically symmetric twisted wall are calculated here and compared with those for the corresponding domain with untwisted wall. Instability conditions are also considered.     

Genetic optimization of modulation characteristics for two twisted nematic liquid crystal spatial light modulators

A single twisted nematic liquid crystal spatial light modulator may suffer from coupled amplitude modulation and a phase modulation capability of less than 2, although almost all panels can achieve . Two twisted nematic liquid crystal panels can be combined in an optical system to produce a total phase modulation of at least 2, and a minimal coupled amplitude modulation. A genetic algorithm is used to optimize the combined modulation characteristics of two liquid crystal panels in a multiplicative architecture. Simulation results and experimental verification are presented which show a substantial reduction in the combined amplitude modulation, and a total phase modulation of 2.     

Nonholonomic constraint between the polarization state of light and the twisted angle of a single-mode optical fiber with linear birefringence

The relation between the polarization state of light propagating in a twisted single-mode optical fiber with linear birefringence and the twist angle of the fiber is discussed for the case where the fiber is stretched in a straight line. It is shown that this relation is of the nature of a nonholonomic constraint. Zh. Tekh. Fiz. 68, 128–129 (November 1998)     

纳米流体液滴内的光驱流动实验及其解析解

在光透过性的流体介质中添加具有高光响应特性的纳米颗粒,可以形成光驱动纳米流体,实现对光能的高效利用.本文针对光驱纳米流体流动行为开展实验观察和理论分析研究,这是实现光驱纳米流动精确调控的理论基础.首先利用粒子图像测速技术对液滴中直径为300 nm的Fe3O4颗粒在不同光源照射下受Marangoni效应诱导的运动进行了实验观测,研究光能向动能的高效转化机制.实验结果表明,当颗粒浓度大于临界数密度时,可诱导出垂向具有对称结构的涡,在液滴底部颗粒由四周向中心运动,顶部则由中心向四周运动,光源频率和颗粒数密度是这一过程的主导因素.随后,针对光强高斯分布的紫外光驱动下大颗粒数密度、特征流速约mm/s的光驱纳米流体,通过Stokes方程和表面张力梯度边界条件实现了其流场分布的解析求解,理论获得的流场分布解析解与实验测量结果保持一致,证实定量理论分析的有效性.最后,讨论了引入表面张力与在液滴底部引入表面压力及体相中集中引入光辐射力的不同驱动模式之间的相关性.这一研究成果为光微流控系统中流动行为的精确调控及光能的高效转化等提供了理论支持.     

On p-adic twisted q-L-functions related to generalized twisted Bernoulli numbers

In this paper, we construct a twisted q-partial zeta function and some twisted two-variable q-L-functions that interpolate q-Bernoulli numbers, β _n,ξ ^(h) (q), and Bernoulli polynomials, β _n,x,ξ ^(h) (x, q), respectively, at negative integers. Using these functions, we prove the existence of a p-adic interpolation function that interpolates the q-generalized polynomials β _n,x,ξ ^(h) (x, q) at negative integers. Consequently, we define a p-adic twisted q-L-function which is a solution of a question of Kim et al. This paper was supported by the Scientific Research Project Administration Akdeniz University.     

基于扭曲向列液晶空间光调制器的矢量光生成

基于扭曲向列型液晶空间光调制器的旋光特性, 根据空间光调制器所加电压和加载相位与旋光角度的对应关系, 设计了可以生成多种涡旋矢量光的通用光路. 利用该原理和光路系统, 在实验上生成了多种携带轴对称相位的矢量光以及图案般复杂的矢量光, 观察和检测了它们的偏振特性, 获得了较好的实验结果. 并且模拟了具有涡旋相位的矢量光的紧聚焦场, 分析了它们的紧聚焦特性. 由于这种生成矢量光的方法光路装置简单、操作容易, 产生矢量光的过程中几乎不损失能量, 并且不存在聚焦过程, 因此在如强激光矢量光束与物质相互作用、激光加速等方面具有重要的应用潜力.     

Reduction of the XXZ model with twisted boundary conditions

The XXZ model with twisted boundary conditions is considered. The method of energy spectrum calculation based on the functional equation for the transfer matrix is analyzed. The Hamiltonian eigenvalues are obtained in an explicit form.     

Analysis of a Sagnac interferometer with low-birefringence twisted fiber

The fiber Sagnac interferometer of low birefringence and twist is analyzed numerically in the linear region. A novel method for measurement of the birefringence of the fiber and the angle of rotation of the axes inside the fiber loop of the interferometer is also presented.