Design Of Novel Metasurface Circular Polarization Converter And Beam Splitte

In recent years,the realization of novel and flexible control of light beams in optical systems has become a goal pursued by researchers,such as light polarization control and beam splitting.However,traditional optical components are mostly made of materials that exist in nature,and their ability to control light characteristics is limited,or they require complex optical components to achieve.In order to find a simple and effective implementation scheme,this reserach combined the metasurface with the circular polarization regulation and beam splitting,and designed metasurfaces to realize the circular polarization device and beam splitting device with novel functions to the incident light by taking advantage of the flexible regulation ability of the metasurface to the amplitude,phase and polarization.The feasibility and functional reliability of the designed metasurface design are verified by simulation,and a simplified,highperformance,and planar design solution is provided for the realization of new optical devices based on metasurfaces.This reserach is mainly based on the finite-difference time-domain(FDTD)method,using gold split-rings to design an anisotropic few-layer metasurface to control the polarization state of circularly polarized light,and realize an asymmetric circular polarization converter.And the purpose of changing the phase delay is achieved by changing the radius of the dielectric nanorods,so as to realize the beam splitter based on the phase gradient metasurface.First,we constructed a three-layer metasurface based on gold split-rings,and introduced anisotropy by rotating the angle of the split-ring in the middle layer,thereby realizing the polarization conversion and asymmetric transmission of circularly polarized light in two adjacent wavelength bands.We used the multiple transmission and reflection theoretical model verify the simulation results,and further analyzed the relationship between the circular polarization conversion through the current characteristics,and calculated the polarization conversion ratio(PCR)and ellipticity to evaluate the circular polarization conversion performance.In addition,the relationship between the refractive index of the dielectric material and the working wavelength,and the influence of the size parameters on the conversion efficiency were also explored.Next,we designed a beam splitter based on the phase gradient metasurface.Firstly,the phases under the nano-cylinders with different radii were measured by simulation,and different phase gradients were designed to achieve different beam splitting angles according to the generalized Snell’s law.By introducing a phase buffer to change the transmittance of the refracted light,phase buffers with different areas were designed to achieve different beam splitting ratios.According to whether the beam splitting angle and beam splitting ratio are the same,four beam splitters with different functions were designed,and the results verify the feasibility of our design method.It also verifies that the designed beam splitter has broadband characteristics and polarization insensitivity characteristics under a wide band with different polarized lights.The work combines traditional optical devices with metasurfaces,which fully embodies the advantages of metasurfaces in small size and easy integration,and the efficient and flexible control capabilities of metasurfaces endow functions that traditional devices do not have.These researchs has potential contributions in many fields such as optical communication,optical sensing,and micro-interferometer.