The Influence Of Pulse Wavelength And Phase On High-order Harmonic And Attosecond Pulses In Two-color Laser Field

The interaction of atoms with a strong laser field will produce some physical phenomena that cannot be explained by traditional perturbation theory,including higher harmonic radiation.Since the 1960 s,People began to obtain laser lines by using harmonic radiation.In particular,the rapid development of ultra-short and super-strong laser technology in recent years has brought strong technical support for harmonic radiation research.At present,theoretical and experimental researches on the generation of high-order harmonic radiation through the interaction of ultra-short and intense laser pulses with atoms are attracting more and more attention,attracting several of the world's best laboratories and experimental teams to engage in research on high-order harmonics,the study of high-order harmonic radiation has made rapid progress and development.In this paper,the generation of high-order harmonics and ultra-short attosecond pulses is controlled by adjusting the relative phases of the drive pulses in the two-color field and the wavelength of the control pulses,and the physical mechanism is explored theoretically.The specific research content is as follows:(1)This paper studies the effect of the control pulse wavelength in the two-color field on the generation of high-order harmonics and ultra-short attosecond pulses,By solving the time-dependent Schr?dinger equation,the higher harmonics generated when the control pulse wavelength is from 600 nm to 2400 nm in a two-color laser field are studied,and the two-color field is superimposed by a 9 fs/1600 nm driving laser pulse and a weaker 6 fs control laser pulse.We performed time-dependent quantum wave packet calculation,by adjusting the wavelength of the control pulse,we can improve the laser field waveform,avoid the destructive interference between the second main peak and the main peak,and improve the higher harmonic conversion efficiency.The influence of the control pulse wavelength is systematically discussed.The results show that the ultra-wideband high-order harmonic spectrum and the ultra-short isolated a second-second pulse can be generated when the control pulse wavelength is 1600 nm.Among them,an isolated pulse of 4.5 as can be obtained by superimposing the first plateau region of the higher harmonic spectrum by a filtering technique.This high-intensity ultra-short pulse provides an unprecedented time resolution,making it possible to observe ultra-fast electron dynamics.(2)Based on the previous study,a two-color laser field is formed by superimposing 9 fs/1600 nm driving laser pulses and 6 fs/1600 nm control laser pulses.Further study of the impact of the driving pulse phase on the generation of high-order harmonics and ultra-short attosecond pulses.Also by solving the time-dependent Schr?dinger equation of the two-color field,the high-order harmonics generated when the driving pulse phase is from 0 ? to 1.9 ? in a two-color laser field are studied.In the cut-off area,the width of the stage can be controlled by changing the phase of the drive pulse.Resulting in an ultra-wide supercontinuum spectrum with a bandwidth of 499 eV,and an ultra-short 3.8 as attosecond pulse can be obtained by superimposing the harmonic spectrum of the plateau region.To further understand the physical mechanism of harmonic generation,classical ionization and quantum time-frequency analysis have also been performed.