A pseudo-spin model for the wall of cytoskeletal microtubule

A pseudo-spin model is intended to describe the physical dynamics of unbound electrons in the wall of cytoskeletal microtubule (MT). Due to the inherent symmetry of the structure and the electric properties in the MT, one may treat it as a one-dimensional ferroelectric system, and describe the nonlinear dynamics of dimer electric dipoles in one protofilament of the MT by virtue of the double-well potential. Consequently, the physical problem has been mapped onto the pseudo-spin system, and the mean-field approximation has been taken to get some physical results.

Steady state ion acceleration by a circularly polarized laser pulse

The steady state ion acceleration at the front of a cold solid target by a circularly polarized flat-top laser pulse is studied with one-dimensional particle-in-cell (PIC) simulation. A model that ions are reflected by a steady laser-driven piston is used by comparing with the electrostatic shock acceleration. A stable profile with a double-flat-top structure in phase space forms after ions enter the undisturbed region of the target with a constant velocity. (C) 2007 Elsevier B.V. All rights reserved.

Multistaged acceleration of ions by circularly polarized laser pulse: Monoenergetic ion beam generation

A multiple-staged ion acceleration mechanism in the interaction of a circularly polarized laser pulse with a solid target is studied by one-dimensional particle-in-cell simulation. The ions are accelerated from rest to several MeV monoenergetically at the front surface of the target. After all the plasma ions are accelerated, the acceleration process is repeated on the resulting monoenergetic ions. Under suitable conditions multiple repetitions can be realized and a high-energy quasi-monoenergetic ion beam can be obtained.

Electron acceleration by a propagating laser pulse in vacuum

Electrons accelerated by a propagating laser pulse of linear or circular polarization in vacuum have been investigated by one-dimensional particle-in-cell simulations and analytical modeling. A stopping target is used to stop the laser pulse and extract the energetic electrons from the laser field. The effect of the reflected light is taken into account. The maximum electron energy depends on the laser intensity and initial electron energy. There is an optimal acceleration length for electrons to gain maximum energy where electrons meet the peak of the laser pulse. The optimal acceleration length depends strongly on the laser pulse duration and amplitude. (C) 2007 American Institute of Physics.

Efficient GeV ion generation by ultraintense circularly polarized laser pulse

The interaction of an ultraintense circularly polarized laser pulse and a solid target is studied by one-dimensional particle-in-cell simulations. Ions at the front of the target are reflected by a moving quasisteady electrostatic field and obtain a relativistic velocity. At a laser intensity of 10(22) W/cm(2), almost half of the laser energy is transferred to ions and GeV ions are obtained. Effects of laser polarization state and target thickness on the laser energy conversion are investigated. It is found that a circularly polarized laser pulse can accelerate ions more efficiently than a linearly polarized laser pulse at the same laser and target parameters. A monoenergetic ion bunch is obtained for the ultrathin target, which is accelerated as a single entity. (c) 2007 American Institute of Physics.

Bubble regime for ion acceleration in a laser-driven plasma

Proton trapping and acceleration by an electron bubble-channel structure in laser interaction with high-density plasma is investigated by using three-dimensional particle-in-cell simulations. It is shown that protons can be trapped, bunched, and efficiently accelerated for appropriate laser and plasma parameters, and the proton acceleration is enhanced if the plasma consists mainly of heavier ions such as tritium. The observed results are analyzed and discussed in terms of a one-dimensional analytical three-component-plasma wake model.

Acceleration of ultra-thin electron layer.Analytical treatment compared with 1D-PIC simulation

In this paper, we apply an analytical model [V.V. Kulagin et al., Phys. Plasmas 14, 113101 (2007)] to describe the acceleration of an ultra-thin electron layer by a schematic single-cycle laser pulse and compare with one-dimensional particle-in-cell (1D-PIC) simulations. This is in the context of creating a relativistic mirror for coherent backscattering and supplements two related papers in this EPJD volume. The model is shown to reproduce the 1D-PIC results almost quantitatively for the short time of a few laser periods sufficient for the backscattering of ultra-short probe pulses.

Study of dynamical behaviour and fermionization of a bosonic gas in funnel potential

This paper presents a funnel external potential model to investigate dynamic properties of ultracold Bose gas. By using variational method, we obtain the ground-state energy and density properties of ultracold Bose atoms. The results show that the ultracold Bose gas confined in a funnel potential experiences the transition from three-dimensional regime to quasi-one-dimensional regime in a small aspect ratio, and undergoes fermionization process as the aspect ratio increases.

超短脉冲激光光束被局域体全息光栅衍射的性质分析

利用二维耦合波理论,分析了超短脉冲激光光束被完全重叠型的局域体全息光栅衍射的时空变化性质,给出了衍射和透射脉冲激光光束沿光栅出射边界的强度时空分布。以LiNbO3晶体为例,数值研究了衍射光脉冲强度沿光栅出射边界的分布和脉冲波形的变化及光栅的总衍射效率受光栅二维尺寸、入射角度、光栅折射率调制度及入射脉冲的脉冲时域半峰全宽等条件的影响而变化的情况。与一维体全息光栅对超短脉冲激光光束衍射的性质,及此光栅对连续光衍射的性质作比较,给出了合理选择光栅参量及入射条件以在光栅出射边界上得到总衍射效率较大且分布较均匀的衍

NUMERICAL STUDY OF DAMMANN ARRAY ILLUMINATORS

The numerical solutions of binary-phase (0, tau) gratings for one-dimensional array illuminators up to 32 are presented. Some fabrication errors, which are due to position-quantization errors, phase errors, dilation (or erosion) errors, and the side-slope error, are calculated and show that even-number array illuminators are superior to odd-number array illuminators when these fabrication errors are considered. One (0, tau) binary-phase, 8 x 16 array illuminator made with the wet-chemical-etching method is given in this paper.

Lau cavity and phase locking of laser arrays

The Lau cavity is the self-imaging cavity with a phase corrector under the Lau reimaging condition. The author proposes the use of the Lau cavity to utilize both the Talbot and the Lau effects for phase locking one-dimensional and two-dimensional diode-laser arrays into a single-lobe coherent beam. Analyses on the self-reproducing of a coherent lasing field and the reimaging of initial incoherent radiation are given.

一种基于平板横向剪切干涉的角位移测量方法

在一种已有的角位移干涉测量技术的基础上,提出一种改进的角位移测量方法。通过选择合适的初始入射角,使从平板前后表面反射的两光束实现剪切干涉。采用一维位置探测器测量光束经透镜会聚后在探测器光敏面上的光点偏移量。根据干涉信号的相位和光点偏移量可以计算出被测物体的角位移。在该测量方案中,引入的一平面反射镜与被测物体的反射面形成光程差放大系统,提高了角位移测量灵敏度。分析了初始入射角对剪切比的影响,并讨论了基于该方案的角位移测量精度。实验结果表明,基于该技术的角位移重复测量精度达到10-8 rad数量级。

Inverse symmetric Dammann gratings

Inverse symmetric Dammann grating is a special grating, whose transition points are reflection symmetric about the midpoint with inverse phase offset in one period. It can produce even-numbered or odd-numbered array illumination when the phase modulations are pi or a specific value. Numerical solutions optimized by the steepest-descent algorithm for binary phase and multilevel phases with splitting ratio from I x 4 to 1 x 14 are given. Fabrication of 1 x 6 array without the zero-order intensity and 1 x 7 array with the zero-order intensity are made from the same amplitude mask. A 6 x 6 output without the crossed zero-orders was achieved by crossing two one-dimensional 1 x 6 inverse symmetric Dammann gratings. This grating may have potential value for practical applications. (C) 2008 Elsevier B.V. All rights reserved.

板条热容激光器的二维热特性

固体热容激光器（SSHCL）作为高功率固体激光器的一个重要发展方向,引起人们广泛关注。数值模拟激光介质板条在热容方式下工作的温度和应力分布是了解该类激光器工作特性的一种有效手段,采用平面应力近似法导出了半导体激光器抽运热容激光介质板的二维温度和应力分布公式,同时也对二维抽运光吸收密度、介质板温度分布和折射率变化进行了分析与讨论。数值计算的结果表明二维效应的温度分布和应力分布要比一维效应给出的分布更均匀。

光学表面的标量散射理论

简要论述了标量散射理论的研究进展做,着重介绍了Beckman的一维标量散射理论和几种典型的多层膜散射模型-非相关表面粗糙度模型、附加表面粗糙度模型和非相关体内不均匀模型,比较了这些模型在中心波长为632.8nm的11层高反膜的散射特性.结果表明,非相关体内的不均匀性引起反射能带边缘散射,反射能带内的散射主要由附加表面粗糙度引起.理想粗糙度对膜系反射带内的散射影响很小,对反射带边缘几乎无影响.预测了标量散射理论的应用领域及前景.