分子取向及组合场相对相位对CO分子产生孤立阿秒脉冲的影响  

Effects of Molecular Orientation and Relative Phase of Combined Fields on Generation of Isolated Attosecond Pulses Using CO Molecules

作　　者：郭中华[1] Guo Zhonghua(School of Electronic Engineering,Lanzhou City University,Lanzhou 730070,Gansu,China)

机构地区：[1]兰州城市学院电子工程学院,甘肃兰州730070

出　　处：《中国激光》2023年第5期142-148,共7页Chinese Journal of Lasers

基　　金：甘肃省自然科学基金(20JR5RA209)。

摘　　要：原子或分子的光电离是强场物理效应的基础。在强场近似下,对于少周期激光脉冲,实验中已证实采用双色激光脉冲场可以增强和相干控制分子的电离。同时,双色场相对相位也是非常重要的参数,借助相位结构的改变来调节分子的电离亦是控制和优化激光与物质相互作用的重要方式。基于此,本文借助Lewenstein模型计算了双色激光脉冲场中利用CO分子高次谐波获得的阿秒脉冲,分析了不同分子取向下相对相位对分子电离以及产生阿秒脉冲的影响。结果显示,平台区域的超连续展宽在任意相对相位下均可产生,但随着分子取向和激光场相对相位的变化,电离较低时易获得超短孤立阿秒脉冲。Objective Isolated attosecond pulses provide an extremely high temporal resolution for studying ultrafast electron dynamics.The highorder harmonic generation(HHG)process by atomic or molecular gas targets remains the most efficient method for obtaining ultrashort isolated attosecond pulses in experiments.The harmonic spectra of molecular gas targets can be significantly extended and exhibit abundant and complex phenomena that merit attention and research.Because of the intrinsic dipole moment of asymmetric structured molecules such as CO,variations in molecular orientation in the laser field cause the ionization process to be very different,which can be used to modulate HHG and produce a supercontinuum spectrum.Furthermore,a twocolor fewcycle laser drive can effectively enhance and control the ionization of molecules in the experiment,allowing the platform area to be extended and the intensity of harmonic radiation to be increased.The relative phase structure of the twocolor field can be changed to further control and optimize its interaction with molecules.Based on the foregoing,this study investigates the effects of CO orientation differences and full relative phase modulation of twocolor fields on achieving ultrashort isolated attosecond pulses.Methods This study calculates the attosecond pulse obtained by driving CO molecules to generate highorder harmonics in a twocolor laser field using the extended Lewenstein model to the oriented molecule CO.The twocolor line polarization fields are used in the calculations.One has a pulse duration of 9 fs,peak intensity of 2.0×1014 W/cm2,and wavelength of 1600 nm;the corresponding values of the other are 5 fs,1.0×1013 W/cm2,and 800 nm,respectively.First,the microscopic ionization properties of CO molecules in the laser field with different orientations(molecular axis and laser field orientation angle from 0°to 180°)are considered in the case of a twocolor laser field with a relative phase of 0.Then,after evaluating the intensity,conversion efficiency,and supercontinu

关 键 词：非线性光学 强场近似 分子的高次谐波 电离率 相对相位 阿秒脉冲 

分 类 号：O437[机械工程—光学工程]