Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences
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Measurement of Wavefront Aberration of Extreme Ultraviolet Lithographic Projection Lens Based on Ptychography
No full textPtychography是一种基于扫描式相干衍射成像的相位恢复技术,实验装置简单,抗干扰能力强。将 Ptychography技术用于投影物镜波像差的检测,并分析了检测不同数值孔径投影物镜波像差所采用的光场传播公式、离散化条件及实验架构。数值仿真与实验结果表明,Ptychography技术用于波像差检测时检测标记的通光率需要在45%~80%范围内;增加标记图案的复杂性并在计算过程中增加配准环节可提高收敛速度与检测精度;波像差检测精度在10~(-3)lambda以内。将Ptychography技术应用于极紫外国家自然科学基金重点项目; 中国科学院青年创新促进会项目Ptychography, a phase retrieval technology based on scanning coherent diffractive imaging, shows such advantages as simple experimental setup and strong anti-noise ability. Ptychography is used in the field of wavefront metrology for projection lens. The formulas of optical field propagation, the conditions of discretion, and the experimental configurations are analyzed in detail for projection lenses with different numerical apertures. Numerical simulations and experimental results show that to achieve reasonable convergence and measurement accuracy, the transmittance of the object should be set between 45% and 80%. Increasing the complexity of the object pattern and adding registration process of probe and object into the iterative algorithm can also improve the convergence speed and the recovery accuracy. The wavefront aberration measurement accuracy can reach 10~(-3)lambda or less. It is feasible to use ptychography in wavefront aberration measurement for extreme ultraviolet lithographic projection lenses
Angle-dependent lubricated tribological properties of stainless steel by femtosecond laser surface texturing
No full textNational Natural Science Foundation of China [61178024, 11374316]; National Basic Research Program of China [2011CB808103]Lubricated tribological properties of stainless steel were investigated by femtosecond laser surface texturing. Regular-arranged micro-grooved textures with different spacing and micro-groove inclination angles (between micro-groove path and sliding direction) were produced on AISI 304L steel surfaces by an 800 nm femtosecond laser. The spacing of micro-groove was varied from 25 to 300 mu m, and the inclination angles of micro-groove were measured as 90 and 45. The tribological properties of the smooth and textured surfaces with micro-grooves were investigated by reciprocating ball-on-flat tests against Al2O3 ceramic balls under starved oil lubricated conditions. Results showed that the spacing of micro-grooves significantly affected the tribological property. With the increase of micro-groove spacing, the average friction coefficients and wear rates of textured surfaces initially decreased then increased. The tribological performance also depended on the inclination angles of micro-grooves. Among the investigated patterns, the micro-grooves perpendicular to the sliding direction exhibited the lowest average friction coefficient and wear rate to a certain extent. Femtosecond laser-induced surface texturing may remarkably improve friction and wear properties if the micro-grooves were properly distributed. (C) 2016 Elsevier Ltd. All rights reserved
Coherent control of the dissociation probability of H-2(+) in omega-3 omega two-color fields
No full textAustralian Research Council (ARC) Discovery Project [DP110101894]; ARC Centre for Coherent X-Ray Science [CE0561787]; National Science Foundation of China [11274326, 61221064, 11134010, 11127901]; ARC Discovery Early Career Researcher Award [DE130101628];We demonstrate that the coherent control of unimolecular reactions by using a waveform-controlled laser fields can lead to a strong modulation on the yield of the reaction. By using a synthesized omega (1800-nm) and 3 omega (600-nm) two-color laser field, the probability of photodissociation of H-2(+) can be strongly modulated by varying the relative phase between the two colors. The dissociation probability maximizes at different relative phases for protons with different kinetic energy, and such energy dependence can also be qualitatively reproduced by our simulation. We attribute the observed dissociation probability modulation to the interference between two different dissociation pathways which start from the same electronic states and end with the same kinetic energy
Design and application of Nd: Glass disc-amplifier as pump source of 5 PW Ti: Sapphire chirped pulsed amplifier
No full text基于蒙特卡罗光线追迹法,进一步研究了钕玻璃片状放大器三维空间聚光腔抽运分布的数值模拟。并且,结合氙灯的充放电回路及辐射光谱、放大自发辐射、以及激光脉冲受激辐射放大等相关数值计算模块,实现了片状钕玻璃放大器由储能至放大的整个过程的动态数值仿真。基于该数值模拟结果,设计研制的钕玻璃片状放大器已用于5PW钛宝石啁啾脉冲放大器的抽运源中,其实验输出结果与数值计算结果基本一致。国家自然科学基金(61378083,61521093)Based on the Monte Carlo rays tracing method, the three dimensional numerical model of pump distribution in Nd: glass disc amplifier is developed. In addition, combined with the other numerical models of Xe flashlamp charge/discharge circuit, amplified spontaneous emission, and laser pulse amplification, the whole work process of Nd: glass disc-amplifier is numerical simulated in detail to realize the whole process of the energy storage to the amplifying of Nd: glass disc amplifier. Based on the results of numerical simulation, the designed Nd: glass disc amplifier is used in the experiments of 5 PW Ti: sapphire chirped pulse amplifier, and the experimental results are in good accordance with the calculated consequence. ? 2016, Chinese Lasers Press. All right reserved
Enhancement of laser intensity and proton acceleration using micro-tube plasma lens targets
No full textAir Force Office of Scientific Research [FA9550-14-1-0085]A hollow, cylindrical, micron-scale structure is proposed to enhance and manipulate the laser plasma interaction. It is shown through 3-D particle-in-cell simulations that the incident laser pulse intensity is enhanced within the tube. A detailed study of the intensification optimizes the tube dimensions and provides a characterization of the in-tube intensity. By coupling the micro-tube plasma lens to a traditional flat interface, we show an increase in on-target intensity. We detail proton energy enhancement as a potential application of the micro-tube plasma lens target, where the tube structure focuses the light and provides additional electrons that enhance the accelerating sheath field. Published by AIP Publishing
Fabrication of polarization-independent single-mode waveguides in lithium niobate crystal with femtosecond laser pulses
No full textNational Basic Research Program of China [2014CB921300]; National Natural Science Foundation of China [61590934, 11134010, 61327902]; Youth Innovation Promotion Association of Chinese Academy of SciencesWe report on fabrication of depressed cladding optical waveguides buried in lithium niobate crystal with shaped femtosecond laser pulses. Depressed cladding waveguides of variable mode-field sizes are fabricated by forming the four sides of the cladding using a slit-beam shaping technique. We show that the waveguides fabricated by our technique allows single-mode propagation of the light polarized in both vertical and horizontal directions. (C) 2016 Optical Society of Americ
Frequency control of the broadband ultrashort terahertz source generated from the laser induced plasma by two-color pluses
No full text实验研究了双色超快强激光场作用于氮气分子束所产生的宽带太赫兹(THz)辐射光谱随等离子体介质的密度和长度的依赖关系, 发现THz辐射的中心频率随等离子体密度提高和长度减小而增大(0.8-1.4 THz), 且谱宽也随之增加(0.78-1.53 THz). 分析和计算表明, 太赫兹光谱的变化由等离子体振荡频率和谱宽决定. 该发现为等离子体宽带太赫兹辐射源的光谱操控提供了新思路.National Natural Science Foundation of China [11274326, 61521093, 61405222, 11134010, 11127901]; National Basic Research Program of China [2011CB808103]The terahertz (THz) radiation becomes an attractive light source utilized in molecular dynamic spectroscopy, remote sensing, medicine, communication and fundamental research. The controlling of the THz spectrum is necessary for the applications. In this paper, a method is proposed for controlling the terahertz spectra generated from the laser induced plasma by two-color pluses based on the contribution of plasma oscillation. The plasma current oscillation can shift the THz spectrum when the length of medium is less than plasma skin depth. Experimentally we use a short length of molecules by means of the molecular beam method. We investigate the changing spectrum of broadband ultrashort terahertz THz generated from a jet of nitrogen (N-2) molecules pumped with the two-color laser pulses following the varying plasma density and plasma length. With the increase of plasma density and the decrease of the plasma length, we observe the increase of THz central frequency (0.8-1.4 THz) and the broadening of the THz spectral width (0.78-1.53 THz). The analysis and the calculation show that the THz spectrum changes due to the frequency and the width of the plasma resonance. This scheme of controlling the THz spectrum by changing the plasma density and length is easier to implement and do not need to use complex shaped optical pulses. The discovery provides a new way of controlling the low-frequency broadband THz spectrum
Numerical investigations of non-collinear optical parametric chirped pulse amplification for Laguerre-Gaussian vortex beam
No full textNational Natural Science Foundation of China [60921004, 11127901, 61378030]; National Basic Research Program of China under grant [2011CB808101]We present for the first time a scheme to amplify a Laguerre-Gaussian vortex beam based on non collinear optical parametric chirped pulse amplification (OPCPA). In addition, a three-dimensional numerical model of non-collinear optical parametric amplification was deduced in the frequency domain, in which the effects of non-collinear configuration, temporal and spatial walk-off, group-velocity dispersion and diffraction were also taken into account, to trace the dynamics of the Laguerre-Gaussian vortex beam and investigate its critical parameters in the non-collinear OPCPA process. Based on the numerical simulation results, the scheme shows promise for implementation in a relativistic twisted laser pulse system, which will diversify the light-matter interaction field. (C) 2015 Elsevier B.V. All rights reserved
Research on superluminal propagation of terahertz wave during femtosecond laser filamentation
No full text通过使用太赫兹(Terahertz,THz)时域光谱系统,探测从不同长度飞秒激光光丝辐射出的THz脉冲,观察到THz波在飞秒激光成丝过程中超光速传输的实验现象。进一步的分析表明:THz波在等离子体光丝区域的折射率小于其在空气中的折射率,这是使得THz波能够在成丝过程中超光速传输的主要原因。由此可以推测:THz脉冲极有可能是在等离子体光丝中进行导引传输的。最后,通过数值模拟获得了光丝区域内的THz本征模式,从而验证了上述推测。国家自然科学基金面上项目; 国家重点基础研究发展规划项目(973计划); 天津市应用基础与前沿技术研究计划(重点项目)In this paper, by investigating the terahertz (THz) waveforms emitted from different lengths of filaments via THz time-domain spectroscopy system (THz-TDS), superluminal propagation of THz wave during filamentation was observed. It implies that the refractive index of the THz wave is smaller than the unity within the filament region, and thus the THz pulse may propagate inside the filament. This hypothesis is supported by further numerical simulation, which demonstrates THz eigenmode inside the plasma filament
Research progress of the control and measurement of the atomic and molecular ultrafast electron dynamics using two-color field
No full text超短超快激光脉冲的出现为人们探索原子分子中超快电子动力学过程提供了强有力的工具.阿秒脉冲和强激光脉冲电场整形技术能够获得电子波包在亚飞秒时间尺度的动力学信息,发展出了一系列阿秒超快光谱学技术,如阿秒条纹相机、阿秒瞬态吸收谱等,成功地应用于原子、分子和固体中电子运动的探测.其中双色激光场就是通过电场整形技术实现电子相干运动控制和探测的一种重要手段,本文综述了中科院上海光机所强场激光物理国家重点实验室近几年来在双色场控制与测量原子分子超快过程方面的研究工作.国家自然科学基金; 国家重点基础研究发展计划; 上海市扬帆计划项目; 上海市科委科技基金; 上海光学精密机械研究所青年特聘研究员项目; 中国科学院青年创新促进会项目资助的课题The advent of the ultrafast laser pulse provides the powerful and efficient tool for probing the ultrafast electron dynamics in atoms and molecules. The various nonlinear process induced by the laser-matter interaction allows one to obtain the electron motion information on the sub-femtosecond time scale. A series of the ultrafast spectroscopic technique, such as attosecond streak camera, attosecond transient absorption spectrum, and etc., have been successfully applied to the probe of electron dynamics in atoms, molecules, and solids. Using two-color field is one of the significant methods to achieve the coherent control and exploring of the electron motion. This paper summarizes recent research activities in the field of the atomic and molecular ultrafast process investigated in State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, including the detection of the electron dynamics of the multi-bound states, measurement of the carrier envelope phase (CEP) and the phase of the attosecond pulse, and the ultrafast electron control with the THz/UV and MIR/IR field. To measure the dynamics of the multi-bound states, a broadband attosecond pulse can be used to ionize the electrons after it is excited by the pump laser. By changing the delay between the pump laser and the attosecond pulse, the measured electrons ionized by the broadband xuv attosecond pulse can present the multi-bound states dynamics simultaneously. The XUV/IR scheme is popularly used in attosecond dynamics measurement. But usually, the IR field is not very strong. We find that, if the IR field is strong enough to induce the above threshold ionization (ATI), the interference between the ATI electron and the electron from XUV pulse can be used to measure the CEP of the attosecond XUV pulse. Besides, if the electron ionized by attosecond pulse can be pushed back to the nuclei, the emission from the recombination can be used to determine the spectral phase of the attosecond pulse, which is an all-optical measurement. We also investigate the two color scheme of THz/UV and MIR/IR fields. With THz/UV two color scheme, very high electron localization can be achieved duration molecular dissociation when we use the UV pulse to excite the electron and the THz pulse to control the following electron movement. When we use the MIR/IR field to control the electron motion during the high harmonic generation, the recollision can be greatly decreased and the single attosecond pulse can be produced with multi-cycle MIR laser field