Alignment-insensitive bilayer THz metasurface absorbers exceeding 100% bandwidth

Area of Science:

• Optics and Photonics
• Metamaterials
• Terahertz (THz) Technology

Background:

• Metamaterial absorbers are crucial for Terahertz (THz) frequencies due to weak natural material interactions.
• Existing THz absorbers often require precise multilayer alignment, hindering performance.
• Achieving wide bandwidth and high efficiency simultaneously remains a challenge.

Purpose of the Study:

• To propose a novel bilayer metasurface absorber immune to layer misalignments.
• To achieve ultra-wideband absorption exceeding 100% fractional bandwidth.
• To offer a robust solution for THz sensing and blackbody applications.

Main Methods:

• Designed a compact bilayer metasurface absorber (thickness ~ λ/6).
• Utilized fractal cross resonators for bandwidth enhancement.
• Incorporated Salisbury Screen and anti-reflection absorption mechanisms.

Main Results:

• Demonstrated misalignment immunity, a significant improvement over existing designs.
• Achieved fractional bandwidth (FWHM) exceeding 100% of the central frequency.
• The absorber exhibits robust performance irrespective of layer alignment deviations.

Conclusions:

• The proposed bilayer metasurface absorber offers a robust and ultra-wideband solution for THz applications.
• Immunity to layer misalignment overcomes a critical limitation in current metasurface absorber technology.
• This work benefits the development of advanced devices like bolometric sensors and planar blackbody absorbers.