Optimized Design Of Meta-lens Based On Phase Superposition In Microwave Region

With the development of nano-manufacture technology,a totally new kind of artificial composite structure,metasurface,is widely researched by scientists and applicated in various regions,which owes special and novel characteristics that can not be found in natural materials.Metasuface is a two dimemsion planar structure,which is composed of amounts of elaborately designed unit cells with period distribution.Unit cells can introduce phase interruption during electromagnetic(EM)wave propagation.It is a significant application of metasurface that utilizing meta-lens to obtian the function of traditional optical lens.In this paper,meta-lenses with different functionality are proposed to control the transmitted EM wave to realize some new characteristics.First,basic theories and concepts are introduced to lay a solid foundation of posterior designs.Generalized Snell's Law is deduced by Fermat's principle.Pancharatnam Berry(P-B)phase principle is analyzed by introducing Poincare sphere.The concepts of electromagnetic wave polarization are presented.Meanwhile,the concepts of vortex beam,converged beam and Bessel beam are introduced.Then,single-layer metallic strips unit cell structure and double-layer metallic split ring unit cell are designed and simulated based on generalized Snells' principle and Pancharatnam Berry(P-B)phase theory.Next,four kinds of meta-lenses based on phase superposition are proposed with designed unit cells:(1)meta-lenses generating vortex beam with different topological charges;(2)meta-lense generating converged vortex beam;(3)meta-lense generating Bessel beam and(4)meta-lenses generating Bessel beam carrying orbital angular momemtum.These different four kinds of meta-lenses not only instead of traditional optical elements,but also realizes frexible controlling of the electromagnetic wave front.Finally,a metacoating structure is designed for axicon to generate longer distance of non-diffraction Bessel beam by two times.After theoretical simulation and experienment measurement,both results show successfully that the proposed meta-lenses all can achieve the preinstall function.And these new bi-functional meta-lenses can be well applied in microwave optical communication and EM wave manipulation.