Reflectionless metasurface with high refractive index in the terahertz waveband

Area of Science:

• Physics
• Materials Science
• Electrical Engineering

Background:

• Terahertz (THz) flat optics aims to replace bulky conventional optical components with ultra-thin, 2D alternatives.
• High refractive index materials for THz flat optics often suffer from high Fresnel reflections due to challenges in controlling relative permeability.

Purpose of the Study:

• To experimentally demonstrate a reflectionless metasurface with a high refractive index at terahertz frequencies.
• To investigate the feasibility of using both weak and good conductors for designing such metasurfaces.

Main Methods:

• Fabrication of a metasurface using a super-fine ink-jet printer with silver paste ink.
• The metasurface consists of 80,036 pairs of cut metal wires on a 5 μm-thick polyimide film.
• Characterization of the metasurface's optical properties at 2.97 THz.

Main Results:

• Achieved a reflectionless metasurface with a high refractive index (5.88 + j1.57).
• Demonstrated extremely low reflectance (1.3%) with high relative permittivity (6.73 + j0.85) and permeability (5.03 + j2.11) at 2.97 THz.
• Confirmed that both weak and good conductors can be utilized for designing high refractive index, reflectionless metasurfaces in the THz band.

Conclusions:

• The developed metasurface overcomes the high reflection limitations in THz flat optics.
• This technology provides a promising platform for 6G wireless communications and advanced THz imaging systems.
• The design approach offers flexibility in material selection for future metasurface development.