共查询到20条相似文献,搜索用时 15 毫秒
1.
Bouhelier A Ignatovich F Bruyant A Huang C Colas des Francs G Weeber JC Dereux A Wiederrecht GP Novotny L 《Optics letters》2007,32(17):2535-2537
We show that interfering surface plasmon polaritons can be excited with a focused laser beam at normal incidence to a plane metal film. No protrusions or holes are needed in this excitation scheme. Depending on the axial position of the focus, the intensity distribution on the metal surface is either dominated by interferences between counterpropagating plasmons or by a two-lobe pattern characteristic of localized surface plasmon excitation. Our experiments can be accurately explained by use of the angular spectrum representation and provide a simple means for locally exciting standing surface plasmon polaritons. 相似文献
2.
In this Letter we present the first (to our knowledge) demonstration of material modification using tightly focused single femtosecond laser vortex pulses. Double-charge femtosecond vortices were synthesized with a polarization-singularity beam converter based on light propagation in a uniaxial anisotropic medium and then focused using moderate- and high-NA optics (viz., NA=0.45 and 0.9) to ablate fused silica and soda-lime glass. By controlling the pulse energy, we consistently machine micrometer-size ring-shaped structures with <100nm uniform groove thickness. 相似文献
3.
研究了电子在聚焦的圆偏振高斯激光束中的非线性汤姆孙散射过程,在此基础上提出了实现单个阿秒脉冲输出的新机理.通过计算机模拟,发现利用紧聚焦的激光脉冲可以有效地增大辐射脉冲链的最高峰和次高峰的峰值强度比即信噪比,从而将阿秒脉冲链变为单个阿秒脉冲输出.紧聚焦情形下,随着驱动激光强度的增大,辐射信号的脉宽变短,信噪比变大;同时当减小激光束腰半径时,辐射信号信噪比也能得到有效改善.研究还发现,利用几个光周期的极短激光脉冲与电子的相互作用也能实现单个阿秒脉冲输出.
关键词:
阿秒脉冲
紧聚焦
信噪比 相似文献
4.
在激光尾场加速中,光学注入是一种有效的可控电子注入机制。然而,低电量、大发散度的电子束特性无法满足实际应用的需要。为获得大电量、高品质电子束提出采用紧聚焦的超高斯激光作为注入脉冲的新型注入方案。研究发现,相比于普通高斯激光,紧聚焦的超高斯激光不仅能够将电子束发散度降低近一个数量级,而且能够保持电子束电荷量不变。通过哈密顿理论模型证实,离轴电子是发散度的主要来源,而紧聚焦的超高斯激光极大地限制了离轴电子的注入,因此有效地降低了电子束的发散度。 相似文献
5.
The dynamics of electrons ionized from high charge states by lasers with intensity >10(20) W/cm(2) have been studied. At these intensities vxB forces drive the electrons subsequent to ionization in a trajectory nearly parallel to the laser propagation direction. This gives rise to large energy gains as the electron rides in phase with the laser field over a long distance. Monte Carlo simulations illustrate that, unlike in case of ionization in sub- and near-relativistic intensity fields (<10(19) W/cm(2)), the electron dynamics in the ultrarelativistic case are strongly influenced by the longitudinal electric fields found near the focus of a tightly focused laser. 相似文献
6.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 33, No. 10, pp. 1144–1149, October, 1990. 相似文献
7.
8.
<正>Tight focusing properties of partially coherent radially polarized vortex beams are studied based on vectorial Debye theory.We focus on the focal properties including the intensity and the partially coherent and polarized properties of such partially coherent vortex beams through a high numerical aperture objective. It is found that the source coherence length and the maximal numerical aperture angle have direct influence on the focal intensity,as well as coherence and polarization properties.This research is important in optical micromanipulation and beam shaping. 相似文献
9.
本文通过数值模拟(3+1)维扩展的广义非线性薛定谔方程,研究了紧聚焦飞秒激光脉冲在诱导石英玻璃的非线性电离过程中电子动量弛豫时间对于该电离过程的影响.计算结果证明电子动量弛豫时间会直接影响入射脉冲在焦点区域所形成的峰值场强、自由电子态密度和能流等参量的分布态势,因此在与实验结果相比较后发现适合于相互作用过程的电子动量弛豫时间的理论值约为1.27 fs.进一步的研究表明,电子动量弛豫时间与逆韧致吸收效应、雪崩电离的概率、等离子体密度、等离子体的自散焦效果以及间接引起的焦平面位置的移动都有着密切的联系.当前的研究结果表明电子动量弛豫时间在飞秒激光脉冲与物质相互作用的过程中发挥着重要作用. 相似文献
10.
作为光波最重要的本征物理属性之一,光场偏振态在研究光与物质相互作用中占有重要地位。矢量光场的波前调控为其聚焦场提供了更加复杂、更加灵活可控的振幅、相位以及偏振态分布,丰富了光与物质相互作用的手段,为材料表征提供了传统线偏振、圆偏振光场所不可替代的研究方法,具有重要的物理意义和实际应用价值。本文将综述矢量光场最新的研究进展,详细介绍矢量光场的偏振态特性、产生方法,以及紧聚焦轴对称矢量光场波前调控在远场小尺度光斑的产生、磁光记录、单分子/颗粒取向探测、任意三维偏振态的产生、高密度数据存储、信息加密以及矢量光场波前重构等方面的重要应用。 相似文献
11.
12.
In this paper attention is given to the effects of primary spherical aberration on the cylindrical polarized vortex beam based on the vector diffraction theory. It is observed that by properly choosing the polarization angle and topological charge one can obtain many novel focal patterns suitable for optical tweezers, laser printing and material process. However, it is observed that the focusing objective with spherical aberration generates structural modification and positional shift of the generated focal structure. 相似文献
13.
Zhangrong Mei 《Optics Communications》2011,284(22):5248-5252
The focal shifts of focused truncated random electromagnetic beams are investigated. Based on the complex Gaussian expansion method for a hard-edged aperture function, the analytical propagation formula of cross-spectral density matrix for a random electromagnetic beam focused by an optical system with a thin lens and a circular aperture is derived. The Fresnel numbers related with the beam and system parameters are defined and used to examine focal shifts. The dependence of the focal shifts on the different Fresnel numbers and polarization distribution are discussed in detail with numerical examples. 相似文献
14.
We report the reduction of sidelobes in tight focusing patterns of radially higher-order Laguerre-Gaussian (LG) beams with nonhelical phase structures. Numerical calculations based on the vectorial Debye theory reveal that a class of annular masks reduces sidelobes in the tight focusing patterns only for radially even-order LG beams. The present scheme produces small focal spots beyond the diffraction limit suitable for application to scanning microscopy, laser fine processing, etc. 相似文献
15.
Yu. N. Eremenko L. S. Mkhitar’yan 《Journal of Experimental and Theoretical Physics》1997,84(5):851-855
We obtain an approximate solution for the drift and oscillatory components of the motion of relativistic electrons in the
field of temporally extended high-power laser light under strong focusing of the light (the size of the focal region is of
the order of the light wavelength). This makes it possible to start numerically integrating the equations of electron motion
near the focal region. We estimate the impact parameters of the electrons when they are still efficiently accelerated in the
focal region.
Zh. éksp. Teor. Fiz. 111, 1554–1562 (May 1997) 相似文献
16.
Radially polarized laser beams in high-resolution microscopy provide an effective means to reduce the focus size below the diffraction limit. Unfortunately, their theoretical manipulation is usually limited to numerical methods. Here, we demonstrate an approach that leads to analytical expressions for the focused electric fields. The approach is based on the discretization of the continuous character of diffraction taking place at the microscope focus. Comparisons with fully numerical calculation are discussed. It results that the new approach accurately reflects the distribution of light within the focal volume with relative deviations that are between 10−4 and 10−13. 相似文献
17.
18.
Z. Yan Y.K. Ho P.X. Wang J.F. Hua Z. Chen L. Wu 《Applied physics. B, Lasers and optics》2005,81(6):813-819
High-order correction terms to the expression of the field of ultra-short tightly focused Gaussian laser pulses are derived.
Terms up to seventh order in the small dimensionless spatial parameter s=1/(k0w00) and first order in the small dimensionless temporal parameter ε=1/(ω0t0) are explicitly presented (ω0=ck0 the central oscillatory frequency, 2t0 the pulse duration, w00 the beam waist radius at the central frequency ω0). To evaluate the correction efficacy, both the corrected and the paraxial field equations are used in detailed simulation
studies of laser/electron interaction dynamics. Special attention is given to the vacuum laser acceleration scheme. The influence
on the electron dynamics due to the diffraction edge field of a tightly focused laser beam is also investigated.
PACS 42.25.Bs; 42.60.Jf; 41.75.Jv 相似文献
19.
20.
A thin-film line array of thermoelectric detectors is applied for the measurement of intensity distribution of focused laser beams. The damage threshold of these detectors is relatively high. They can tolerate 50 μsec pulses with intensities as high as 3·105 W/cm2. High resolutions can be achieved by fabricating line arrays having a large number of thermoelectric junctions with distances as small as 5 μm between centers. 相似文献