Design And Study Of Nanostructure Based On Phase Modulation Of Catenary Optics

The modulation of the beam has always been a hot topic of research.Conventional optical components used to control electromagnetic wavefronts have become a hindrance to the integration and miniaturization of modern optical devices due to their certain thickness and large volume.Although artificial electromagnetic metamaterials can achieve subwavelength-scale electromagnetic wave modulation thanks to their extraordinary electromagnetic response characteristics,their structures are too complicated for fabrication with the defects of high loss and narrow bandwidth.The metasurface structure extended from three-dimensional metamaterials to two-dimensional flat surface overcomes the above problems and has received eager attention for its excellent performance.In this paper,the catenary metasurface structure based on P-B phase regulation is studied,a single unit of this metasurface structure can produce a continuous 0-2π phase change.Unlike discrete nano-antennas,which require discrete phase sampling,the catenary structure greatly simplifies the complexity of structure design and fabrication,which has great advantages for future applications.Moreover,the catenary structure can realize the transformation of the beam polarization state,which effectively adjust the wavefront of the beam,and also has a wideband phase modulation characteristic.The specific content of this article includes:1.This paper introduces the research status of metasurface structure and three typical methods and principles of phase modulation and theoretically analyzes the internal mechanism of phase modulation of catenary metasurface structure2.In this paper,a catenary deflection array structure with deflection angles of 30°,45° and 60° is constructed.The electric field distribution of the transmission field and the radiation pattern in the far field are simulated analyzed.And the data of the transmission field is depolarized by MATLAB calculation program.The results fully demonstrate that the co-polarization component in the transmission field is not deflected and still propagates along the original direction.And there is a true deflection is in the cross-polarized portion of the incident wave when it passes through the catenary structure.3.With the unique phase modulation characteristics of catenary structure to the incident beam,a circular,single-spiral and double-helical catenary supersurface structure are separately designed using Python computer program in this paper.The simulation results show that these structures can effectively control the incident beam in the near-infrared band,producing a high-order Bessel beam with a wide response bandwidth,which has good regulation effect in the 260THz-300 THz frequency range.4.In this paper,the cross-polarization conversion efficiency of the catenary structure is studied in detail.By optimizing the period of the catenary structure,the material,and adding the reflective layer and the antireflection layer,the cross-polarization conversion efficiency of the catenary structure increased from the initial 2% to 19%(theoretical limit is 25%).Finally,the method of improving the cross-polarization conversion efficiency proposed in this paper is verified by a single-helical catenary model.