Ultrawideband 3-bit multifunctional metasurfaces by completely spin-decoupled meta-atom

Area of Science:

• Metamaterials
• Electromagnetics
• Optics

Background:

• Achieving distinct wavefront reconstruction for orthogonally polarized electromagnetic (EM) waves is crucial for modern wireless communications.
• Current circularly polarized wavefront modulation devices face limitations due to conjugate symmetric phase responses from rotation-induced geometric phases.

Purpose of the Study:

• To design a spin-decoupled meta-atom for independent modulation of left-hand and right-hand circularly polarized waves across a broadband frequency range.
• To demonstrate the feasibility of this strategy for advanced applications like meta-holograms and metalenses.

Main Methods:

• Designed a novel meta-atom structure enabling independent phase control for left-hand and right-hand circularly polarized incident waves.
• Incorporated diagonal curvature-induced and conventional geometric phases to achieve spin-dependent phase modulation over the entire 2π range.
• Developed a four-channel imaging method to boost meta-hologram information capacity.

Main Results:

• Achieved independent tailoring of left-hand and right-hand circularly polarized waves over a broadband range of 12-28 GHz (80% fractional bandwidth).
• Demonstrated spin-dependent phase modulation covering the full 2π range.
• Successfully designed, manufactured, and tested three prototypes, validating the proposed strategy through calculations and experiments.

Conclusions:

• The proposed spin-decoupled phase modulation strategy is feasible and effective for broadband applications.
• This approach offers significant potential for advancements in information metasurfaces, metalenses, and wireless communications.