Design Of Photonic Spin Filters In Ultraviolet Band Based On Metasurfaces

Metasurfaces can achieve precise modulation of the phase,amplitude and polarization properties of electromagnetic waves,and therefore have attracted much attention in the field of optical devices.The ultraviolet(UV)circularly polarized light has the functions of modulating the helical structure of nanobiotic and improving the precision of lithography.However,the optical system for obtaining UV circularly polarized light has the disadvantages of low integration and its polarized light purity cannot meet the demand of high precision.Herein,combining with the technical characteristics and advantages of metasurfaces,a design scheme of photonic spin filter in UV band based on metasurfaces of double layer and single layer was proposed.The model and related parameters were simulated by using the finite difference time domain method,and the mechanism of metasurfaces regulating UV circularly polarized light was discussed.Firstly,the concept of photonic spin filters based on metasurfaces was introduced.The characteristics and advantages of polarized optical devices based on metasurfaces were summarized,and the relationship between the structure of metasurfaces unit cells and the performance of polarized optical devices was analyzed.Meanwhile,the calculation principle of finite difference time domain method and the design process of polarized optical devices based on metasurfaces was introduced,which have laid the foundation for the subsequent simulation design and analysis.Secondly,based on geometric phase principle,the photonic spin filters in UV band based on double layer metasurfaces were designed.The photonic spin filters with the operating wavelength of 370 nm and 230 nm were simulated by using the finite difference time domain method.By adjusting the shape and size of the structural unit cells,the optimal parameters of the structural unit cells were obtained.By designing the phase distribution of the double layer metasurfaces,the influence of the metasurfaces on the performance of UV photonic spin filters was studied.The simulation results show that the integrated design of the photonic spin filter can be realized by optimizing the structure of the metasurfaces,and the circularly polarized light with high polarization purity can be extracted by the design.Combined with the geometrical phase principle,the mechanism of the phase and polarization of incident light regulated by double layer metasurfaces was discussed.Finally,based on spin-multiplexing principle,the photonic spin filters in UV band based on single layer metasurfaces were designed.The photonic spin filters with the operating wavelength of 370 nm and 230 nm were simulated by using the finite difference time domain method.By adjusting the shape and size of the structural unit cells,the optimal parameters of the structural unit cells were obtained.By designing the phase distribution of the single layer metasurfaces,the influence of the metasurfaces on the performance of UV photonic spin filters was studied.The simulation results show that the integrated design of the photonic spin filter can be realized by optimizing the structure of the metasurfaces,and the transmittance of circularly polarized light is improved by the design on the basis of extracting the desired chirality with high polarization purity.Combined with the spin-multiplexing principle,the mechanism of the phase and polarization of incident light regulated by single layer metasurfaces was discussed.