3-Bit coded metasurface for linear and circular polarized vortex beam broadband modulation based on dual-frequency multistage resonance

A metasurface design scheme is proposed based on reflective double vertical U-shaped resonators. Compared to planar resonators with the same parameters, vertical meta -atom can excite magnetic dipole resonance and quaternary resonance respectively at low and high frequency to achieve stable wideband phase shift and unique free regulation. Vertical meta -atoms can be applied as 3-bit coding elements in linearly polarized (LP) and circularly polarized (CP) states with bandwidths of 0.7–1.1 THZ and 0.55–1.5 THZ, respectively. At the same time, as a half-wave plate, the deflection conversion rate is 95%, the relative bandwidth is 69%, and the operating Angle is 80°. In order to verify the application capability of the designed meta -atom, the excitation and separation of multi-stage vortex beams are performed in the wide frequency range of LP and CP using the coded convolutional addition method. The designed meta -atom only needs to regulate a single structural parameter to fully satisfy the requirements of 3-Bit broadband coding under LP and CP incidence, so it has multi-type polarization wave universality and ultra-wide working bandwidth. Meanwhile, the method can be effectively applied to optical band and microwave band.