High-efficiency terahertz beam scanning based on topologically optimized freestanding metasurfaces.

Area of Science:

• Physics
• Electrical Engineering
• Materials Science

Background:

• Dynamic beam scanning is crucial for terahertz (THz) frequencies due to high path attenuation.
• Bi-layer passive metasurfaces enable beam tuning via relative twisting but suffer from low energy efficiency and instability.
• Existing methods face challenges with insertion loss and diffraction sensitivity to metasurface orientation.

Purpose of the Study:

• To enhance energy efficiency and stability in dynamic beam scanning using passive metasurfaces.
• To develop a novel metasurface design that overcomes the limitations of bi-layer structures.
• To achieve wide-angle beam steering with minimal sidelobes in the terahertz band.

Main Methods:

• Topological optimization was employed to design a pair of freeform, freestanding metasurfaces.
• The substrate was removed to improve impedance matching and reduce insertion loss.
• Relative rotation of the metasurfaces generated moiré patterns for beam steering.

Main Results:

• The proposed metasurfaces achieved beam scanning within a ±55° field of view.
• Average energy efficiency reached 57%, with efficiency fluctuations within 13%.
• The scanning process demonstrated minimal apparent sidelobes.

Conclusions:

• The developed freeform, freestanding metasurfaces significantly improve energy efficiency and stability for dynamic terahertz beam scanning.
• This approach offers a promising solution for overcoming the limitations of traditional bi-layer metasurfaces.
• The technology holds potential for applications in next-generation wireless communication systems.