非对称波形激光驱动的氢原子高次谐波频移及控制  

Frequency shiftand control ofhigh-order harmonicsof H atom driven by anasymmetric laser pulse

作　　者：魏博宁 焦志宏[1] 周效信[1] Wei Bo-Ning;Jiao Zhi-Hong;Zhou Xiao-Xin(College of Physics and Electronic Engineering,Northwest Normal University,Lanzhou 730070,China)

机构地区：[1]西北师范大学物理与电子工程学院,兰州730070

出　　处：《物理学报》2022年第7期91-98,共8页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11765018,11764038,91850209)资助的课题。

摘　　要：提出了一种利用非对称波形激光脉冲与原子相互作用在隧穿区发射高次谐波谱的大频移方案.通过数值求解偶极近似下的三维含时薛定谔方程,研究了该激光驱动氢原子发射的高次谐波特性.结果表明,利用上升沿与下降沿不同的非对称激光驱动氢原子所发射的高次谐波在截止位置附近发生了大的频率红移和蓝移,通过改变激光脉冲的上升沿或下降沿,能调控谐波的频移量.产生频移的原因是激光脉冲上升沿或下降沿对谐波贡献的不同所致,当下降沿发射谐波的贡献大于上升沿的贡献时,谐波发生红移,反之则发生蓝移.通过改变激光脉冲波形,在隧穿电离区能够调控截止位置附近原子发射的高次谐波频率,对于给定的某一阶谐波,调控的范围可从奇次阶到邻近偶次阶之间的任意频率处.A scheme of the large frequency shift for high-order harmonic generation(HHG)produced by atomic gas driven by an asymmetric laser pulse is proposed in the tunneling ionization regime.By numerically solving the three-dimensional time-dependent Schrodinger equation in the dipole approximation,we theoretically investigate the characteristics of HHG emitted from hydrogen atom driven by the laser pulse with different rising and falling times.Our results show that the HHG spectra of atomic H in cutoff region present a strong redshift and blueshift.The shift can be adjusted by varying the rising time or falling time of the laser pulse.The time frequency analysis,reveals that the reason for the frequency shift comes from different contributions from the rising time or falling time in the asymmetric laser pulse.If the contributed harmonics during the falling time is larger than that during the falling time,the red shift of HHG occurs.otherwise the blue shift appears.Therefore,by shaping the laser pulse waveform,the frequency of atomic HHG for a given order in the cutoff region in the tunneling ionization regime is tunable,which can cover the frequency range from the odd order to the adjacent even order.

关 键 词：非对称激光波形 高次谐波 红移 蓝移 

分 类 号：O562[理学—原子与分子物理]