基于正交偏振场的双光学控制方案获得孤立阿秒脉冲产生  

Isolated attosecond pulse generation from a double optical gating scheme based on orthogonal polarization field

作　　者：吕孝源 朱若碧 宋浩 苏宁 陈高[1] Lü Xiao-Yuan;Zhu Ruo-Bi;Song Hao;Su Ning;Chen Gao(School of Science,Changchun University of Science and Technology,Changchun 130022,China)

机构地区：[1]长春理工大学理学院

出　　处：《物理学报》2019年第21期65-72,共8页Acta Physica Sinica

基　　金：吉林省基础研究计划基金(批准号:20170101046JC)资助的课题~~

摘　　要：利用强场近似理论开展了基于正交偏振场的双光学控制脉冲与氦原子相互作用产生高次谐波和阿秒脉冲发射的理论研究.这里的正交偏振场由具有一定时间延迟、振幅相等且呈正交偏振的两束线偏振脉冲构成,双光学控制脉冲是在正交偏振场的驱动脉冲电场方向附加一束线偏振二次谐波脉冲.研究发现,若合理地调整正交偏振场中两束线偏振脉冲之间的时间延迟及附加二次谐波场与驱动脉冲电场之间的相对相位,可得到效率较高且在整个平台区及截止位置附近皆连续的高次谐波发射谱,傅里叶变换后实现了143 as孤立短脉冲的辐射.相比于利用两束反旋圆偏振脉冲附加二次谐波场的双光学控制方案,该方案不仅克服了对入射驱动脉冲脉宽和强度的限制,而且避免了偏振门前端光学周期引起的气体介质电离不利于谐波相位匹配的弊端.Isolated attosecond pulses make it possible to study and control the ultrafast electron processes in atomsand molecules.High order harmonic generation(HHG)is the most promising way to generate such pulses,benefiting from the broad plateau structure of the typical HHG spectrum.In previous HHG studies on thepolarization gating scheme,atomic ionization caused by the laser cycles before the polarization gate not onlyplaces a limit on the pulse width and intensity of the driving laser,but also affects the phase matching ofharmonics generated in a polarization gate.According to these,in this paper we propose a new double opticalgating scheme,in which the polarization of the laser pulse changes from linear to elliptical and back to linearagain.Thus,only the linearly polarized field in the leading of the pulse contributes to high harmonic generation.By using a strong field approximation theory,we first simulate high order harmonic and attosecond pulsegeneration from helium atom irradiated by a double optical gating pulse based on the orthogonal polarizationfield.Here the orthogonal polarization field consists of two linearly polarized pulses with a certain time delay,orthogonal polarization directions and equal amplitudes.And for the double optical gating pulse,the secondharmonic of the driving field is added to an orthogonal polarization field with an appropriate phase and energy.It is found that the high harmonic spectrum with higher efficiency and supercontinuum plateau is obtained byreasonably adjusting the parameters of the combined pulse.After inverse Fourier transform,an isolated 143-aspulse with higher intensity can be realized by superposing supercontinuum harmonics from the 50th to the150th order.Compared with the double optical gating scheme proposed by Chang et al.(Zhao K,Zhang Q,Chini M,Wu Y,Wang X,Chang Z 2012 Opt.Lett.37 3891),our scheme not only overcomes the limit on thepulse duration and intensity of the incident pulse laser,but also avoids the harmonic phase mismatching in theprocess of the propagation

关 键 词：高次谐波 阿秒脉冲 正交偏振场 双光学控制 

分 类 号：O436.3[机械工程—光学工程] O562[理学—光学]