| High-order harmonic generation is a nonlinear effect produced in the interaction of strong laser field with atoms and molecules.High-order harmonic generation are both an important source of attosecond pulses and can be used for molecular orbital imaging.High-order harmonic generation provides a way to study the electrodynamics process of the attosecond-angstrom scale and becomes a frontier in laser physics research.In this paper,the non-perturbative scattering theory is used to study the harmonic spectrum generated from atoms and molecules driven by two-color counter-rotating circularly polarized laser field,and an iteration algorithm of electronic orbital imaging in molecules by harmonic energy spectrum is discussed.The contents and results are as follows:According to the analytical formula of high-order harmonic generation,the harmonic spectra of hydrogen atoms in the two-color counter-rotating circularly polarized laser field are calculated,and the variation of harmonic order and degree of polarization with the driver frequency is confirmed.It is found that the harmonics generated in-)4,3,2(?? two-color counter-rotating circularly polarized field are of the orders nnn???,15,14,13 and the harmonic polarization degree of the +1 orders is the same as the fundamental field polarization,and the harmonic polarization of the-1 orders is the same as the polarization of the harmonic driver.Further research discloses that the +1 orders harmonic absorbs(n+1)photons from the fundamental field and absorbs n photons from the harmonic driver,thus has the same polarization as the fundamental frequency field;the harmonics of the-1 orders are the opposite.In addition,we find that changing the laser intensity ratio of two colors does not change the order of the emitted harmonics and the degree of polarization.For high-order harmonics generated from driven molecules,the order selection also depends on thesymmetry of valence electron distribution.An iteration algorithm that reconstructs the electron orbital in molecule using harmonic energy spectra is discussed.The analytical formula for the generation of high-order harmonic generation contains the molecular orbital wave function part and the dynamics part describing the motion of electrons in the laser field.The iteration algorithm we developed eliminates the effects of electrodynamics by means of the scaling law,and extract the orbtial information of molecules from the harmonic spectra.This method is different from the existing methods that determining the electron dynamics by referring to that of atoms similar binding energy. |
