Research On The Airy Beam Excitation In Microwave Region Based On Metasurface

Non-diffracted beams,such as Bessel beams,Mathieu beams,and Airy beams,do not spread as they propagate.This property is particularly useful in many applications including imaging,micromanipulation and optical transfection.However,Airy beams have more special properties,namely self-bending(self-acceleration).The devices used to generate Airy beams have been bulky and difficult to integrate in systems.As a new type of artificial electromagnetic material,the metasurface has the advantages of sub-wavelength thickness,small size,and easy implementation.More importantly,the use of the metasurface can manipulate the amplitude and phase of the electromagnetic wave.This paper uses the metasurface to realize the generation and control of the Airy beam.The main research contents of this paper are as follows:First,the related theory of Airy beam is studied,including the basic solution of Airy wave packet,and then the Airy function based on Airy wave packet basic solution is studied.Because the ideal Airy beam has non-diffraction characteristics and moreover infinite energy,this paper truncates the ideal Airy beam,and then gives an expression of the finite energy Airy function.Finally,the three important properties of the Airy beam are mathematically described and practical applications are given.Second,the excitation of circularly polarized Airy beams was studied.Firstly,the transmission phase modulation unit was designed based on the electromagnetic resonance unit.The designed unit cell includes an electrical resonant structure with double split rings and a three-layer metasurface with circular patches as an amplitude modulator.By arranging the electromagnetic resonance structure in accordance with the the phase and amplitude distributions of Airy function,the phase modulation and the phase-amplitude modulation of the Airy beam are achieved,and the self-healing characteristics of the Airy beam are verified,and three effective methods are used for deflection control.The control methods of changing the proportion of every section of the metasurface and using the generalized refraction law are effective.Finally,the excitation of linearly polarized Airy beams was studied.Firstly,another efficient multi-layer linearly polarized transmission phase modulation unit was designed,and the design and simulation of the phase modulation Airy beam excitation metasurface was performed.It produced a good wavefront control for the normally incident linearly polarized wave.Thus,Airy beam excitation is successfully achieved.Then,using the designed amplitude modulator based on split ring as the unit,a seven-layer phase-amplitude modulation metasurface is constructed.According to the simulation results,the designed amplitude modulator has great effect on expanding the working band.The introduction of the new phase factor method among the three control methods has the most obvious effect.