Circularly Polarized Molecular High Order Harmonics -Generation and Applications in Attosecond Science

Andre D. Bandrauk, PhD, O.C., FRSC, FAAAS

Faculte des Sciences,

Universite de Sherbrooke, Quebec, Canada

地点: 北京大学 物理楼中楼215会议室

时间: 2017年11月6日 (星期一) 15:00-16:30

MHOHG, Molecular high order harmonic generation is a highly nonlinear nonperturbative response of molecules to ultrashort(fs) intense(I>1014 W/cm2) laser pulses leading to multiphoton ionisation and laser induced electron recollisions in linear polarisation.MHOHG is suppressed with intense single circularly polarized pulses but has been shown in 1995 to be generated with co- or counter-rotating pairs of bichromatic ( w1/w2=n1/n2) circularly polarised pulses leading to the generation of circularly polarised attosecond(10-18 s) pulses, the time scale of electron motion in atoms and molecules. Parallel computer simulations of TDSEs (Time Dependent Schroedinger Equations) coupled with Maxwell’s equations show that molecules are the ideal systems for circular polarised harmonic and attosecond pulse generation due to lower rotational symmetries than atoms. The TDSE simulations confirm the electron-parent ion recollision mechanism in the presence of bichromatic circular pulses and maximum circular polarised MHOHG efficiency is obtained when the net time dependent electric field of the combined pulses is compatible with molecular symmetry. The resulting circularly polarised attosecond pulses are shown to generate in molecules coherent attosecond quantum electron currents from which one can create intense attosecond magnetic pulses for studying ultrafast magnetism and dynamical symmetry in molecules.

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