Ultra-broadband infrared metasurface absorber: comment

Area of Science:

• Metamaterials and Nanophotonics
• Electromagnetic Wave Absorption
• Optical Engineering

Background:

• Gradient-metasurface-based absorbers (GMBAs) have been proposed for ultra-broadband perfect absorption.
• Previous studies suggested broadening absorption bandwidth by increasing metasurface layers.

Purpose of the Study:

• To re-evaluate the absorption performance of GMBAs reported by Guo et al.
• To identify potential oversights in the calculation of total absorption in GMBAs.

Main Methods:

• Analysis of cross-polarization reflection in GMBAs.
• Recalculation of total absorption considering all polarization components.

Main Results:

• Cross-polarization reflection was found to be neglected in the original study.
• A single-layered GMBA exhibits only two absorption peaks at 8.09 μm and 9.84 μm.
• The actual absorption rates at these peaks are 58.4% and 57.1%, respectively, not perfect absorption.

Conclusions:

• The initial claims of ultra-broadband perfect absorption in the proposed GMBAs are not supported when cross-polarization is considered.
• The actual absorption performance of the single-layered GMBA is significantly lower than reported.
• Further refinement of GMBA designs is needed to achieve high absorption across a broad spectrum.