The Semi-integer High-order Harmonic Emission And Isolated Attosecond Pulse Generation From Ar Atom

The research of high-order harmonic generation(HHG)has developed dramatically with the development of intense laser,recently.In particular,HHG driven by spatially inhomogeneous field and bichromatic counter-rotating circularly polarized(BCCP)laser field has been become a research hotpot.This paper theoretically studies the generation of semi-integer harmonics of the Ar atom in BCCP laser field.Rules for the photons number absorbed by the semi-integerorder harmonic from the left-handed laser field is given by conservation of angular momentum,and the semi-integer-order harmonic emission mechanism is clarified using the transition image.Next,this thesis explores the high-order harmonic spectrum generated by the interaction of two crossed linearly polarized lights in spatially inhomogeneous field from an Ar atom,and the dependence of the polarization direction of the synthesized isolated attosecond pulse in the three-dimensional space on the spatial inhomogeneous parameter is given.These results are conducive to the control of high-order harmonic polarization in future experiments and the improvement of attosecond pulse detection technology.In this paper,the high-order harmonic emission of argon atom is studied in detail from the following parts,which are summarized as follows:(1)In BCCP laser field,the HHG of Ar atom is studied.When the wavelength of left-handed circularly polarized laser does not change,as the wavelength of righthanded circularly polarized laser increases,the HHG spectrum will split.With the splitting of the harmonic spectrum line,we can observe that the harmonic order is no longer only the integer order,but also accompanied by the non-integer-order harmonics,including the semi-integer order.Then we studied the right-handed circularly polarized laser wavelength of 533 nm,320 nm,228 nm and 177 nm,respectively.The HHG from the left and right-hand laser absorbed photon number in the laser field numerical statistics by the conservation of angular momentum,and we also explain the generation of the semi-integer orders by using quantum leap image.(2)In two cross-linearly polarized laser fields,the HHG of argon atoms in a twodimensional inhomogeneous field and the polarization direction of synthesized isolated attosecond pulse in three-dimensional space are studied.The ‘water window’ of HHG is extending,and ellipticity of the harmonic platform is close to zero,with the increase of the inhomogeneous parameter on single direction.And the angle between the isolated attosecond pulse synthesized and the x-y plane increases with the change of the inhomogeneous field parameter in the y direction.