Study On Terahertz Wide-field Focusing Planar Lens Based On Metasurfaces

Terahertz wave has the characteristics of low photon energy,strong penetration to non-polar molecules,and can effectively reflect the internal composition and content information of substances.It has important application prospects in safety inspection,nondestructive testing,radar detection,high-speed communication,cancer diagnosis and even astronomy and other practical applications.However,the existing terahertz lenses are all refracting/reflecting lenses,which have problems such as large size,bulkiness,complex installation and adjustment,etc.,and it is difficult to meet the needs of the increasingly developed terahertz telephoto systems and radars for lightweight and small-volume optical systems.Therefore,it is urgent to carry out in-depth research on lightweight terahertz wide-field planar lens and its components,so as to provide core components for lightweight terahertz telescope systems and terahertz radars.Therefore,in this thesis,a terahertz wide-field metasurface lens group is designed with both wide field of view and high resolution,which has important practical value for the development and application of integrated and lightweight terahertz optical systems.The main research work of this thesis is as follows:(1)The research status of traditional terahertz wide field lens,terahertz metasurface lens and wide field metasurface flat field lens was investigated,the shortcomings and problems to be solved were analyzed,and the research objectives and contents of this paper were proposed.(2)The aberration theory was studied,and the generalized Snell's law and PB phase were deduced.Damped least square method and vector diffraction angle spectrum theory were studied.(3)Based on the damped least square method,an optimal design of a large field of view silicon based all-dielectric terahertz wide field metasurface lens group was carried out for the terahertz wave with a wavelength of 79.36 ?m.The tolerance analysis was carried out,and the precision requirements of device installation were determined.(4)Based on the vector angle spectrum diffraction theory,the terahertz wide-field metasurface lens group was simulated,and the focusing and imaging with a sidelobe ratio of less than 15% and close to the diffraction limit(1.22?)were realized within a50° field of view.(5)The metasurface unit structure based on the PB phase was designed,and the terahertz wide-field focusing planar lens structure design based on the metasurface was completed.The process of processing terahertz metasurface lenses was studied,and the device preparation and characterization were completed.