Simulation Study On Harmonic Radiation In The Interaction Of Ultra-intense Laser And Foil Target

With the improvement of laser intensity,the field of interaction between laser and matter has expanded to relativity,in which the interaction of strong laser with gas or solid matter to induce the generation of higher harmonics is the rapid development of the field.At the same time it has become an important method for the development of extreme ultraviolet(EUV)and X-ray coherent light sources and attosecond pulse,with attractive and wide application prospects.Particle simulation of high-order harmonic radiation caused by the interaction between super-intense laser and foil target is carried out by using commercial software VSim 6.2,including one-dimensional simulation of laser and foil target by normal incident,two-dimensional simulation of laser and foil target by oblique incidence under different parameters,the content is as follows:First,based on the known high-order harmonics generated by the coherent synchrotron radiation mechanism in the transmission direction of the thin foil target,the harmonic radiation caused by the reflection direction is further studied by one-dimensional particle simulation.The spatial distribution of the high-order harmonic radiation generated by ultra-intense laser driving the foil target in the transmission and reflection directionshas been researched.It is found that in the ultra-intense laser driving the foil target interaction model,The coherent synchrotron emission mechanism in the transmission direction leads to harmonic generation.At the same time,there is still the harmonic emission driven by the relativistically oscillating mirror mechanism in the direction of its reflection,which proves the new conclusion that the two harmonic generation mechanisms coexist in the process of ultra-intense-laser and foil target interaction.The influence of the thickness,plasma density and laser intensity on the harmonic order was discussed under the two kinds of mechanisms.It is found that the degree of dependence of the harmonics on the parameters under different generation mechanisms is different.Then,the two-dimensional particle simulation of laser and foil target by oblique incidence induced high-order harmonic generation is carried out.By comparing the distributions of the harmonic radiation field generated by the incident and oblique incident laser-foil targets,the harmonics of the even harmonics in the incident case are investigated.By comparing the effects of different incident angles on the harmonic radiation,it is found that the harmonic radiation induced by the relativistically oscillating mirror mechanism and the harmonics induced by the coherent synchrotronemission mechanism in the transmission direction.The radiation has a completely different dependence on the laser incident angle.The results of this study will provide selective parameter basis for the development of coherent EUV and soft X-ray light source technologies.