吸收多个远紫外光子生成的高次谐波的多重截止结构  

Multiple cutoffs in high harmonic generation via multi-XUV-photon absorption

作　　者：俞祖卿 何峰[1] 

机构地区：[1]激光等离子体教育部重点实验室、IFSA协同创新中心、上海交通大学物理与天文系,上海200240

出　　处：《物理学报》2016年第22期114-119,共6页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11104180,11175120,11121504,11322438,11574205)资助的课题~~

摘　　要：本文通过数值求解含时薛定谔方程研究He+在远紫外和红外激光场作用下产生高次谐波的过程.在电子隧穿并从红外激光场获得能量后,其在与母离子碰撞过程中可能吸收额外的远紫外光子,并导致高次谐波中出现以远紫外光子能量为间隔的多重截止结构.我们进一步通过傅里叶频谱分析的方法证实了这一结构产生的物理机制;并分析了高次谐波的多重截止频率强度和远紫外强度的关系.我们的研究为产生高能量谐波提供了一种方案.High harmonic generation（HHG） is one of the most fundamental processes in the interaction of strong laser fields with atoms and molecules.Because of wide applications of HHG,for example,imaging atomic or molecular orbitals,visualizing chemical reactions,synthesizing a single attosecond pulse,the HHG attracts huge attentions in both theories and experiments.The HHG can be explained by the famous three-step model：first,the laser field bends the Coulomb potential and the electron tunnels out;second,the electron is accelerated in the laser field and gains kinetic energy;Third,the energetic electron recombines with the parent ion and release its energy as high energetic photons.The HHG can be tailored by controlling the each step.In this paper,we conceive a strategy to control the third step.We simulate the HHG when He＋is exposed to the combined few-cycle Ti-Sapphire（800 nm） IR femtosecond laser pulse and XUV laser pulse by numerically solving the time dependent Schr？dinger equation.The simulation shows that after the electron tunnels out and gains energies from the infrared laser field,extra XUV photons may be absorbed during the electron and parent ion recombination,contributing multiple cutoffs separated by XUV photon energies in the high harmonic spectrum.This scenario is confirmed by time-delay-dependent HHG in the time-frequency representation,and by the power scaling of the cutoffs＇ intensities as a function of the XUV intensity.

关 键 词：高次谐波 多重截止 多远紫外光子吸收 

分 类 号：O56[理学—原子与分子物理]