Gradient force pattern, focal shift, and focal switch in an apodized optical system

In this paper, the evolution of the gradient force pattern, focal shift, and focal switch induced by a three-portion pure phase-shifting apodizer is numerically investigated in detail. The results show that the proposed apodizer may induce tunable gradient force on the particles in the focal region, focal shift, and focal switch. By adjusting the geometrical parameters of the phase-shifting apodizer, multiple traps may occur with changeable distance between them, and the shape of the optical trap also evolves evidently. More interestingly, for certain geometrical parameters of the proposed apodizer, by changing the phase shift of inner annular portion, the considerable focal shift may occur with focal switch accompanying, which is discussed to show that this kind of apodizer may be a very promising method of transporting trapped particles. © 2005 Elsevier GmbH. All rights reserved.

Focal shift in focused radially polarized ultrashort pulsed laser beams

Beginning with a beam coherence polarization (BCP) matrix, we obtain an analytical intensity expression for radially polarized ultrashort pulsed laser beams that pass through an apertureless aplanatic lens. We also investigate the intensity distribution of radially polarized beams in the vicinity of the focus. The focal shift of these beams is studied in detail. The focal shift depends strongly on Z(F) that coincides with pi times the Fresnel number. (c) 2007 Optical Society of America.

环形非稳腔倒向波抑制镜抑制效果的数值模拟

对环形非稳腔激光器做数值计算模拟，给带有倒向波抑制(RWS)镜的环形非稳腔激光器的设计提供了数值参考。通过自洽方程，用Matlab计算带有倒向波抑制镜的环形非稳腔正、倒向波的稳定过程。改变腔长、放大率等参数来计算，发现使用倒向波抑制镜能明显提高正向波的输出，并能抑制倒向波。气体分子的多普勒频移导致正、倒向波的频率变化。频率分开的越小，竞争越大，抑制效果越好，正向波输出功率则有所下降。对于特定的结构，存在最佳的放大率，使正向波的输出最大。计算结果表明，倒向波抑制镜的引入能增大环形非稳腔输出功率。计算结果对实

加速度对激光双频干涉仪测量误差的影响

为了减少由于加速度所导致的激光双频干涉仪测量误差,引入二阶多普勒频移,建立了由被测物体加速度所引起的测量误差的理论模型。仿真结果表明,在0.4s时间内0.6g加速度所引起的累积误差可达2.5 nm左右,这对于纳米精度的测量是不应忽视的; 初速度不为零时加速运动会引起更大的误差,而减速运动所引起的误差则相对小。通过实验验证,所测的误差变化趋势与理论模拟比较吻合。