Polarization-independent multi-channel retroreflective metasurfaces based on extraordinary optical diffraction

Area of Science:

• Metamaterials and Nanophotonics
• Electromagnetics and Optics
• Diffraction Engineering

Background:

• Metasurfaces enable retroreflection via phase gradients.
• Existing metasurface retroreflectors often exhibit polarization-dependent performance.
• Achieving polarization-independent multi-channel retroreflection remains a challenge.

Purpose of the Study:

• To propose and demonstrate a polarization-independent multi-channel metasurface for high-efficiency retroreflection.
• To utilize extraordinary optical diffraction (EOD) for novel retrodirective characteristics.
• To overcome the polarization dependency of conventional metasurface retroreflectors.

Main Methods:

• Design of a unary unit cell metasurface for wave canalization into specific diffraction orders.
• Structural engineering to suppress unwanted diffraction orders (-1st order maintained) under oblique incidence.
• Fabrication and measurement of a proof-of-principle prototype operating at 20.0 GHz.

Main Results:

• Demonstrated polarization-independent retroreflection in three channels.
• Achieved high retroreflection efficiency of approximately 90% across specified angles (±48.6° and 0°).
• Verified performance through both simulations and experimental measurements.

Conclusions:

• The proposed metasurface design strategy enables efficient, polarization-independent, multi-channel retroreflection.
• This method offers facile planar fabrication and potential for extension to THz and optical frequencies.
• The EOD-based approach provides a robust solution for retrodirective applications.