Theoretical Study On The Dependence Of High Order Harmonic Generation From Atoms On The Carrier Envelope Phase Of The Orthogonal Two-color Laser Fields

High order harmonics generated by atoms are an effective way to obtain mesa coherent extreme ultraviolet(XUV)or even soft X-ray light source under the action of strong laser field.Because of their advantages of short duration,adjustable wavelength and wide spectrum,high order harmonics are very suitable for observing the internal structure of atoms and ultrafast dynamic processes in high time and high space resolution optical processes.Therefore,in recent years,it has become a hot issue in strong field physics to study the characteristics of higher harmonics generated by different types of laser drives.In this paper,by solving the two-dimensional time-dependent Schrodinger equation numerically,the generation process of higher harmonics of He atom driven by the quadrature polarization frequency doubling two-color laser field is studied theoretically.The effects of intensity ratio,relative phase and pulse width on the intensity and cutoff position of higher harmonic spectrum were investigated.The results show that,different from the linearly polarized two-color laser field,when the two laser intensities of orthogonal polarization two-color field are close,the harmonic radiation intensity has a high dependence on the relative phase of the laser,and the difference of the harmonic intensity of different phases is up to 2 orders of magnitude.In order to explain this physical phenomenon,we use time-frequency analysis and time-dependent electron wave packet probability density to give the motion law of the electron.We find that the difference of harmonic intensity depends on the probability of heavy collision of the two-dimensional electron wave packet back to the parent nucleus.In addition,we also investigate the possibility of controlling the quantum path of He atom to produce higher harmonics by using orthogonal polarization two-color laser field.The results show that the harmonic emission of long-orbit electrons can be suppressed effectively by adjusting the relative phase of laser.Thus,the interference between short and long tracks is reduced,and the high harmonics with good resolution are obtained.This control is not significantly dependent on the laser pulse width.