利用正交偏振双色场产生孤立阿秒脉冲  

Generation of Isolated Attosecond Pulse Using Orthogonally Polarized Two-Color Fields

作　　者：孙佳楠 尹燕奔 陈高[1] Sun Jianan;Yin Yanben;Chen Gao(School of Physics,Changchun University of Science and Technology,Changchun 130022,Jilin,China)

机构地区：[1]长春理工大学物理学院,吉林长春130022

出　　处：《光学学报》2023年第13期286-294,共9页Acta Optica Sinica

基　　金：吉林省自然科学基金(20220101028JC)。

摘　　要：利用强场近似理论开展了正交偏振双色场与氦原子相互作用产生高次谐波和阿秒脉冲的理论研究。正交偏振双色场由少周期的4 fs钛宝石驱动脉冲激光和与它偏振方向垂直的8 fs倍频控制脉冲构成。研究发现,通过合理选择两束脉冲之间的相对相位,能够控制高次谐波发射过程中长、短电子轨道的选择。当相对相位调整为1.2π时,平台谐波主要来自短轨道电子的贡献,由于其运动时间短、波包扩散少,且没有与长轨道电子谐波产生干涉,沿驱动脉冲电场方向的高次谐波谱具有较高强度和较小调制幅度的超连续平台区,通过对第120次到第180次超连续谐波进行傅里叶变换,可产生脉宽为54 as的高强度孤立阿秒脉冲。所提方案对组合脉冲相对相位的选取要求并不严苛,在0.3π的变化范围内皆可获得脉宽较短的孤立阿秒脉冲,同时控制脉冲电场强度的变化对上述数值模拟结果的影响也很小。Objective Attosecond pulses are currently the shortest radiation pulses that can be obtained,and their ultra-fine temporal and spatial resolution has become an important tool to study ultra-fast electron dynamics in atoms and molecules.At present,the high-order harmonic generation from the interaction of femtosecond pulses with atoms or molecules is the only effective means to produce desktop attosecond pulse radiation sources.Thus,researchers have proposed many advanced techniques for generating isolated attosecond pulses in experiments and theories,such as few-cycle laser pulses,dual-color or multi-color fields,and polarization gating schemes.The orthogonally polarized dual-color fields,composed of two linearly polarized pulses with different wavelengths and perpendicular polarization directions,have become an effective way to control electron motion with the characteristics of polarization modulation and two-color field.By numerically simulating the interaction between helium atoms and orthogonally polarized dual-color fields composed of 4 fs/800 nm driving pulses and 8 fs/400 nm gating pulses,we obtain a 54 as high-intensity isolated attosecond pulse.The advantage of this scheme is that a single quantum trajectory(short trajectory)can be selected during a single atomic response.Additionally,the isolated attosecond pulse is less affected by the relative phase between the two pulses and by the change in the electric field intensity of the gating pulse.Methods The high-order harmonic generation from the interaction of the orthogonally polarized two-color field with helium atom is studied numerically by the strong field approximation theory.Attosecond pulses are synthesized by superimposing the super-continuum harmonic spectra.The ionization rate of helium atoms is calculated through the ADK tunneling ionization theory model,and the classical trajectory of electrons is calculated using the semi-classical three-step model theory proposed by Corkum.Results and Discussions An orthogonally polarized bichromatic field

关 键 词：超快光学 高次谐波产生 阿秒脉冲 正交偏振双色场 电子轨道 

分 类 号：O436[机械工程—光学工程]