Study On The Ellipticity Of The Attosecond Pulse Superposed By High-order Harmonic Generating By 2-dimension He Atom

With the development of the laser technology,the peak intensity of laser pulse we obtained are more and more strong and the width of the pulse are more and more short.When the peak intensities of the laser pulse are so high that the corresponding laser field can compare with the Coulomb force of the electrons in an atom.Atoms and molecules interacting with such intense laser field would therefore give rise to some new phenomena,such as High-order Harmonic Generation(HHG).According to the previous study,the linear polarized laser field could only generate linear polarized harmonic.But it's not applicable for the chiral molecule recognition.People proposed a new laser field so-called bicircular laser field(which consist of two coplanar counter-rotating circularly polarized fields with different frequency)to generate circularly polarized and elliptically polarized harmonic.The high order harmonics which are generated by bicircular laser field can be used in exploring chiral recognition,and researching time-resolved magnetization dynamics and spin currents.In view of the application of circularly polarized and elliptically polarized harmonics,the research of bicircular laser field has been intensified.The main research work of this paper is summarized as follows.We used the split-operator method to numerically compute the 2-dimensional time-dependent Schr?dinger equation(TDSE)of the s-state He atom interaction with bicircular laser field.And then we can research the spectra of the HHG generated by this laser field and the ellipticity of the APTs superposed by this harmonics.Firstly,we could control the ellipiticity of APTs by adjusting the intensity ratio between the two components in bicircular laser field.And we found that,the higher the ratio the fundamental frequency field sites,the highly ellipticity of the attosecond we could obtain.Then we demonstrate another effective way to obtain highly elliptically polarized APTs.We use a circular-elliptical laser field,which consists of a circularly polarized field with its coplanar counter-rotating elliptical harmonic pulse to pump He atom to generate HHG.We show that the polarization of APTs depends evidently on the ellipticity of harmonic laser field.And nearly circular APTs can be obtained with a proper ellipticity of the 3? component for ?-3? driving laser field.So our results proved we could obtained high elliptical APTs with s-state atom.