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Strong white light emission is observed from femtosecond laser propagation in air. The divergence angle of the white light emission is measured to be about 5mrad. Young's double-slits and a Michelson interferometer are used to investigate the coherence. The wavelength components of the white light emission are identified to have a good spatial coherence and a coherence time of about 0.5ps. 相似文献
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Generation of Broadband High Harmonics through Linear Mode Conversion in Inhomogeneous Plasmas 下载免费PDF全文
The generation of high order harmonics from an inhomogeneous ovderdense plasma target irradiated by an ultrashort intense laser pulse is studied by numerical simulation. During such interaction, ultrafast electron bunches are generated and excite electron plasma oscillations as they pass through the overdense target. These plasma oscillations will emit high-frequency electromagnetic emission by linear mode conversion. Instead of the integer harmonies generation, the emission appears with a broadband and even continuous spectrum corresponding to the electron plasma frequency range of the inhomogeneous plasma density. 相似文献
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H2+He流体混合物在高温高压下由于氢的离解化学反应形成由H2,H,He三种粒子构成的混合体系,此时粒子间的相互作用较为复杂,离解能也会由于粒子间的这种复杂相互作用而降低.本文利用自洽流体变分理论来研究部分离解区H2+He流体混合物的高温高压物态方程,模型考虑了各种粒子间的相互作用及由温致和压致效应引起的离解能降低的自洽变分修正,并通过自洽流体变分过程对非理想的离解平衡方程求解得到粒子数密度分布,进而对自由能求导获得体系的热力学状态参量.计算结果与已有的冲击波实验数据、蒙特卡罗模拟及其他理论计算进行了比较. 相似文献
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Separating lights into different paths according to the polarization states while keeping their respective path's polarizations with high purification is keen for polarization multiplex in optical communications. Metallic nanowire gratings with multi-slits in a period are proposed to achieve polarized beam splitters(PBSs) in reflection and diffraction. The setting of multi-slits largely reduces the reflection of photons with a transverse magnetific field via the plasmonic waveguiding effect, which leads to highly polarized output lights with extinction ratio larger than 20 dB in each channel. The proposed reflection/diffraction PBSs enrich the approaches to control the polarization states with the advantages of wide incident angles and flexible beam splitting angles. 相似文献
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在现有的一维粒子模拟程序的基础上发展了带光电离和碰撞电离及蒙特卡罗两体碰撞的模拟程序(1D PIC-MCC). 用此程序模拟研究了短脉冲激光与He气靶相互作用时电子和离子的加速过程. 研究表明当强激光与过临界密度的微米厚度的平面靶相互作用时,靶前表面物质将被激光脉冲前沿迅速离化;新生的电子被激光场有质动力加速成为高能电子,这些电子穿入到靶内,通过电子碰撞电离离化靶内物质;一部分高能电子穿透靶后,会在靶的后表面形成强的电荷分离场,该场迅速离化靶后表面物质,同时使得后表面离子得到加速. 部分穿透靶的超热电子将被电荷分离场重新拉回靶内,在靶的前后表面振荡. 一些振荡电子在此过程中得到电荷分离场加速,离开前表面,在前表面也形成电荷分离场,使前表面离子得到加速.
关键词:
激光等离子体
光电离和碰撞电离
电子加速
离子加速 相似文献
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一维应变条件下金属层裂的实验研究 总被引:1,自引:0,他引:1
材料的层裂是由两个相向的拉伸应力作用引起材料断裂的一种现象,是一个被普遍关注的力学问题。本文中主要对层裂研究的意义、历史和现状,一维应变条件下层裂的原因、表征、加载方式及测试技术等问题进行了综述,并讨论了影响层裂强度的几种主要因素。 相似文献
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Temperature Measurements of Condensed Gaseous Hydrogen-Helium Mixtures under Multi-Shock Compression 下载免费PDF全文
Temperatures of multi-shock compressed gaseous hydrogen-helium mixtures with a mole component H2 :He=1:1.21 up to 7100 K are measured at pressures up to 10 GPa by means of an instantaneous optical pyrometer. The gas mixtures are shocked from environmental temperature at the initial pressure 20 MPa. The measured second-shock temperature differs from the predictions of the non-dissociation model by up to 40% and is in good agreement with that of the dissociation model, indicating that a considerable amount of molecular dissociation occurs. 相似文献
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Effects of Laser Intensities and Target Shapes on Attosecond Pulse Generation from Irradiated Solid Surfaces 下载免费PDF全文
Single attosecond pulses can be generated when an intense laser pulse focused in a volume of a few cubic wave- lengths (λ^3) is reflected from a solid plasma surface. With relativistic two-dimensional particle-in-cell simulations, we investigate the effects of the incident laser intensity and the target surface profiles on attosecond pulse generation. Usually the width of the reflected attosecond pulse decreases and its electromagnetic energy density increases with increasing laser intensity, while the energy conversion efficiency to the attoseond pulse decreases, By changing the target surface profile, such as using a convex surface or adding proper preplasma, one can further shorten the attosecond pulse duration and meanwhile increase its energy density. 相似文献