Terahertz technology has a broad application prospect in communication systems.Digital codingmetasurface can control electromagnetic wave propagation and has been widely concerned.Most of the reported codingmetasurface achieve full 2π phase coverage of reflected or transmitted LP(linearly polarized)and CP(circularly polarized)waves based on PB(geometric phase)or transmission phase,limiting the flexibility of terahertz wave regulation.This paper proposes a metasurface element structure consisting of three layers,from top to bottom:the metal pattern structure layer,intermediate medium layer,and metal base layer.In this paper,a metasurface element is proposed by combining the propagation phase and geometric phase.The metasurface is designed to generate vortex beams based on the transmission phase mechanism under the incident of online polarized terahertz waves,and multi-vortex beams are generated by convolution operation.According to the geometric phase principle,phase coverage in the 2π range can be achieved by rotating the metal pattern structure layer under the circularly polarized terahertz wave incident.The metasurface is designed to generate vortex beams based on the transmission phase mechanism under the incident of online polarized terahertz waves,and multi-vortex beams are generated by convolution operation.According to the geometric phase principle,phase coverage in the 2π range can be achieved by rotating the metal pattern structure layer under the circular polarized terahertz wave incident.The metasurface can be properly arranged by using phase coding.The designed metasurface can deflect the reflected beam,showing good flexibility.Secondly,the designed metasurface generates vortex beams at multiple frequency points.At 0.9 THz,vortex beams with topological charges l=1 and l=2 are generated with mode purity of 68.9％and 69.5％.At 1.2 THz,vortex beams with topological charges l=1 and l=2 are generated with mode purity of 91.03％and 87.2％.In addition,the deflection vortex beam is generated by convolution,and the focusing coding metasurface is designed to realize the focusing function.In this paper,we propose a terahertz multi-dimensional phase-controlled reflection metasurface,which combines the propagation phase with the geometric phase to realize the regulation of two independent polarized channels.The results show that the designed metasurface provides a multi-degree-of-freedom method for polarization and phase manipulation of terahertz waves,which has broad application potential in terahertz systems.
TerahertzPhase controlVortex beamTerahertz deflection of beam
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