Short-pulse laser absorption via J x B heating in ultrahigh intensity laser plasma interaction

An analytical fluid model for JxB heating during the normal incidence by a short ultraintense linearly polarized laser on a solid-density plasma is proposed. The steepening of an originally smooth electron density profile as the electrons are pushed inward by the laser is included self-consistently. It is shown that the JxB heating includes two distinct coupling processes depending on the initial laser and plasma conditions: for a moderate intensity (a <= 1), the ponderomotive force of the laser light can drive a large plasma wave at the point n(e)=4 gamma(0)n(c) resonantly. When this plasma wave is damped, the energy is transferred to the plasma. At higher intensity, the electron density is steepened to a high level by the time-independent ponderomotive force, n(e)> 4 gamma(0)n(c), so that no 2 omega resonance will occur, but the longitudinal component of the oscillating ponderomotive field can lead to an absorption mechanism similar to "vacuum heating." (c) 2006 American Institute of Physics.

Optical levitation measurements with intensity-modulated light beams

Illumination of an optically levitated particle with an intensity-modulated transverse beam induces a transverse vibration of a particle in an optical trap. Based on this, the trapping force of a trap can be measured. Using an intensity-modulated longitudinal levitating beam causes a particle to move vertically, allowing for the determination of some aerodynamic parameters of a particle in air. The principles and the experimental phenomena are described and the initial results are given. (C) 1997 Optical Society of America.

Guiding neutral atoms with two current-carrying wires and a vertical bias field on the atom chip

We demonstrate the guiding of neutral atoms with two parallel microfabricated current-carrying wires on the atom chip and a vertical magnetic bias field. The atoms are guided along a magnetic field minimum parallel to the current-carrying wires and confined in the other two directions. We describe in detail how the precooled atoms are efficiently loaded into the two-wire guide. We present a detailed experimental study of the motional properties of the atoms in the guide and the relationship between the location of the guide and the vertical bias field. This two-wire guide with vertical bias field can be used to realize large area atom interferometer.

Readout of a real-time hologram in bacteriorhodopsin film with high diffraction efficiency and intensity

A scheme for the readout of a hologram recorded in bacteriorhodopsin film with high diffraction efficiency and intensity is suggested and demonstrated. Two weak coherent continuous beams function as the recording beams, and a strong light pulse is used to read the real-time hologram. The width of the readout light pulse is modulated to be short compared with the erase time of the reading beam; the time space between two adjacent pulses is ensured to be longer than the time the beams take to recover the hologram, and high diffraction efficiency and intensity (similar to 11 mW/cm(2)) can be obtained. (C) 1996 Optical Society of America.

精确标定光弹调制器的新方法

针对现有光弹调制器标定方法的不足，提出了一种精确标定光弹调制器的新方法。首先利用起偏器、波片、光弹调制器和检偏器构成标定光路．通过寻找探测信号基频分量的极大值进行粗略标定，使光弹调制器的峰值延迟量处在1．841rad附近。然后撤走波片形成光弹凋制器的精确标定光路．在检偏器旋转90°前后获得探测信号的直流分量和二次谐波分量。最后利用这两种探测信号的直流分量和二次谐波分量精确地计算出光弹调制器的峰值延迟量。实验验让了此光掸调制器标定方法，实验结果表明其标定误差仅为0．7％。在此光掸凋制器标定方法中．光弹调制器

Collimation testing using axial intensity

We proposed a new method of measuring the degree of collimation of laser beam using axial intensity information near paraxial focus. Preceding methods for collimation testing are mainly either based on self-imaging or interferometric techniques. The new method is to employ the diffraction behavior of noncollimated wave in circular aperture diaphragm. The principle of the proposed method and experiment results are presented. Due to simplicity of the method and its low cost, it is a promising method for checking the collimation of laser beam. (c) 2005 Published by Elsevier GmbH.

消除正弦相位调制干涉仪中光强调制影响的全光纤干涉仪

在激光二极管(LD)正弦相位调制(LD-SPM)干涉仪中,通过注入电流调制激光二极管波长的同时,光源输出的光强也被调制,成为测量误差的主要来源之一。提出一种新的消除激光二极管正弦相位调制干涉仪中光强调制影响的干涉仪,给出了具体的理论分析。该干涉仪采用全光纤结构,有效减小外界干扰对干涉测量的影响;采用容易实现的前置信号处理电路和实时相位检测器对干涉信号进行处理,消除了激光二极管光强调制产生的测量误差;同时实现了物体微小位移的高精度实时测量,测量的重复精度达到1 nm。实验结果与其他消除光强调制影响的方法测得

Intensity-moments characterization of general pulsed paraxial beams with the Wigner distribution function

On the basis of the space-time Wigner distribution function (STWDF), we use the matrix formalism to study the propagation laws for the intensity moments of quasi-monochromatic and polychromatic pulsed paraxial beams. The advantages of this approach are reviewed. Also, a least-squares fitting method for interpreting the physical meaning of the effective curvature matrix is described by means of the STWDF. Then the concept is extended to the higher-order situation, and what me believe is a novel technique for characterizing the beam phase is presented. (C) 1999 Optical Society of America [S0740-3232(99)001009-1].