Orbital Angular Momentum(OAM)waves are characterized by helical wave fronts and orthogonality between different modes.Therefore,OAM waves have huge potential in improving wireless communications'channel capacity a...Orbital Angular Momentum(OAM)waves are characterized by helical wave fronts and orthogonality between different modes.Therefore,OAM waves have huge potential in improving wireless communications'channel capacity and radar imaging's resolution.Consequently,the generation and application of OAM waves have attracted a lot of attention.And many methods are proposed to generate OAM waves.Although antenna array is the most popular method of generating OAM waves,OAM waves generated by antenna array have redundant modes.However,all advantages of OAM waves are closely related to infinite OAM modes.Thus,to better apply OAM waves to wireless communications and radar,it is very important to reduce unnecessary OAM modes and improve the OAM mode purity.In order to improve the OAM mode purity,two combined antenna arrays composed of X direction antenna and Y direction antenna array are proposed in this paper.The X direction antenna array and the Y direction antenna array are supplied by the excitations with the same amplitude and fixed phase shift.The overall phase shift of the X direction antenna array isπ/2 more or less than that of the Y direction antenna array.The results of formulas and antenna models in CST show that the combined antenna arrays can generate OAM waves with less redundant modes in x component,y component and z component.Besides,the z component carries pure OAM modes.展开更多
A systematic study of the aperture efficiency and mode constituent for orbital angular momentum(OAM) vortex beam generated by digital metasurface is presented. The aperture efficiency and OAM spectrum are computed for...A systematic study of the aperture efficiency and mode constituent for orbital angular momentum(OAM) vortex beam generated by digital metasurface is presented. The aperture efficiency and OAM spectrum are computed for different bit numbers. It is found that the aperture efficiency declines for digital metasurface due to the phase quantization error,especially for 1-bit device. Fortunately, the OAM spectrum is barely affected by phase quantization and the designated main mode keeps dominant for different bit numbers, indicating that high purity OAM vortex beam can be generated by digital metasurface. Besides, the influence of topological charge l is also investigated. For a fixed metasurface, the radiation performance deteriorates sharply with the growing of l and the parasitic OAM mode becomes dominant at certain angle.At last, a prototype of 1-bit metasurface was simulated, fabricated and measured in anechoic chamber. The simulation and experiment results verify the correctness of the numerical analysis.展开更多
In this study,we propose and demonstrate an all-fiber orbital-angular-momentum(OAM)mode encoding system,where through helical fiber gratings(HFGs),binary symbols are encoded to or decoded from two OAM modes with topol...In this study,we propose and demonstrate an all-fiber orbital-angular-momentum(OAM)mode encoding system,where through helical fiber gratings(HFGs),binary symbols are encoded to or decoded from two OAM modes with topological charges(TCs)of-1 and+1,respectively.We experimentally validate that the OAM mode generated by a clockwise-helix HFG(cHFG)can be converted back into fundamental mode by using an HFG with a helix orientation opposite to that of the cHFG,i.e.,ccHFG.Benefited from utilization of the HFGs,the proposed OAM mode encoding system has a low cost,low insertion loss,high mode conversion efficiency,and polarization independence.To the best of our knowledge,this is the first demonstration of the HFGs-based all-fiber OAM mode encoding/decoding scheme,which may find potential applications in optical communication and quantum communication as well.展开更多
基金supported by the National Science Foundation of China(NSFC 62073334).
文摘Orbital Angular Momentum(OAM)waves are characterized by helical wave fronts and orthogonality between different modes.Therefore,OAM waves have huge potential in improving wireless communications'channel capacity and radar imaging's resolution.Consequently,the generation and application of OAM waves have attracted a lot of attention.And many methods are proposed to generate OAM waves.Although antenna array is the most popular method of generating OAM waves,OAM waves generated by antenna array have redundant modes.However,all advantages of OAM waves are closely related to infinite OAM modes.Thus,to better apply OAM waves to wireless communications and radar,it is very important to reduce unnecessary OAM modes and improve the OAM mode purity.In order to improve the OAM mode purity,two combined antenna arrays composed of X direction antenna and Y direction antenna array are proposed in this paper.The X direction antenna array and the Y direction antenna array are supplied by the excitations with the same amplitude and fixed phase shift.The overall phase shift of the X direction antenna array isπ/2 more or less than that of the Y direction antenna array.The results of formulas and antenna models in CST show that the combined antenna arrays can generate OAM waves with less redundant modes in x component,y component and z component.Besides,the z component carries pure OAM modes.
文摘A systematic study of the aperture efficiency and mode constituent for orbital angular momentum(OAM) vortex beam generated by digital metasurface is presented. The aperture efficiency and OAM spectrum are computed for different bit numbers. It is found that the aperture efficiency declines for digital metasurface due to the phase quantization error,especially for 1-bit device. Fortunately, the OAM spectrum is barely affected by phase quantization and the designated main mode keeps dominant for different bit numbers, indicating that high purity OAM vortex beam can be generated by digital metasurface. Besides, the influence of topological charge l is also investigated. For a fixed metasurface, the radiation performance deteriorates sharply with the growing of l and the parasitic OAM mode becomes dominant at certain angle.At last, a prototype of 1-bit metasurface was simulated, fabricated and measured in anechoic chamber. The simulation and experiment results verify the correctness of the numerical analysis.
基金National Key Research and Development Program of China(2023YFB2804900)National Natural Science Foundation of China(62375134)+2 种基金Japan Society for the Promotion of Science(JP24K21609,JP23K22816)Amano Institute of TechnologyNatural Science Research of Jiangsu Higher Education Institutions of China(22KJB510030)。
文摘In this study,we propose and demonstrate an all-fiber orbital-angular-momentum(OAM)mode encoding system,where through helical fiber gratings(HFGs),binary symbols are encoded to or decoded from two OAM modes with topological charges(TCs)of-1 and+1,respectively.We experimentally validate that the OAM mode generated by a clockwise-helix HFG(cHFG)can be converted back into fundamental mode by using an HFG with a helix orientation opposite to that of the cHFG,i.e.,ccHFG.Benefited from utilization of the HFGs,the proposed OAM mode encoding system has a low cost,low insertion loss,high mode conversion efficiency,and polarization independence.To the best of our knowledge,this is the first demonstration of the HFGs-based all-fiber OAM mode encoding/decoding scheme,which may find potential applications in optical communication and quantum communication as well.
