Extreme Ultraviolet Vortices Based On High Harmonic Generation

Light field regulation is an important means to realize the precise physical regulation of the interaction between light and material.It includes phase,amplitude,polarization,pulse shaping and so on.It is necessary to develop new light field for realizing multi-dimensional regulations.In recent years,many new optical fields have been found,such as phase vortex and polarization vortex.Phase vortex,which carries orbital angular momentum(OAM),is widely used in super-resolution imaging,optical communications and quantum optics.Special polarization is a property of polarization vortex that is widely used in many areas of science and technology,such as laser processing and particle acceleration.At present,the generation and application of vortex light are limited to infrared and visible bands,while vortex light in extreme ultraviolet(EUV)to X-ray bands is rarely studied.The regulation of atomic and molecular quantum states provides opportunities for the development of short-wave vortices that also have potential applications.However,the generation of short-wave vortices is very difficult.Now,there are only a few ways to generate EUV vortices light.In this paper,EUV vortices light is obtained by high harmonic generation(HHG)and explores its properties.Firstly,it is researched that the characteristic of HHG spectrum and the structure of single order EUV phase vortex.The experimental results demonstrate that the EUV vortex could be transferred from near-infrared driven laser during the highly nonlinear interaction and the reason is that the central intensity of the HHG spectrum is zero.Meanwhile,it is founded that the EUV vortex spot which has a specific OAM is larger than the EUV gaussian light.Secondly,the polarization vortex harmonic spectrum and single order light source are studied in this paper.The experimental results show that the polarization vortex is similar to phase vortex and the generation of EUV vortices based on HHG.By optimizing and comparing the generation of high order harmonics of vortex field and gaussian field,it is found that there is a similar phase matching mechanism.In our experiment,it indicates that EUV phase vortex and polarized vortex can be mapped to HHG by changing the characteristics of the driving optical field.The short-wave vortices that generated by HHG can be extended to the regulation of the interaction between light and atoms and molecules.It also provides an important technique for the attosecond vortex and the formation of attosecond vector.