Seven-octave ultrabroadband metamaterial absorbers via quality-factor-weighted mode density modulation

Area of Science:

• Acoustics and Wave Phenomena
• Materials Science
• Metamaterials

Background:

• Wave propagation dynamics are significantly influenced by absorption.
• Achieving ultrabroadband absorption, especially across low frequencies, presents a significant challenge.
• Existing metamaterial absorbers (MMAs) struggle to balance low-frequency performance with broad bandwidth.

Purpose of the Study:

• To present a novel metamaterial absorber (MMA) design for ultrabroadband absorption.
• To demonstrate simultaneous spectral coverage across a seven-octave range (100 to 12,800 Hz).
• To introduce and utilize the concept of quality-factor-weighted (Q-weighted) mode density for enhanced absorption.

Main Methods:

• Engineering the quality-factor-weighted (Q-weighted) mode density.
• The Q-weighted mode density comprehensively considers mode density, resonant frequencies, radiative loss, and intrinsic loss.
• Optimizing the number of resonant modes and managing intrinsic losses within the metamaterial structure.

Main Results:

• Achieved near-perfect absorption across an ultrawide bandwidth from 100 to 12,800 Hz (a seven-octave range).
• Demonstrated an intensive Q-weighted mode density across the ultrawide bandwidth.
• Successfully enabled ultrabroadband absorption with high efficiency.

Conclusions:

• The proposed Q-weighted mode density approach is effective for governing broadband absorption properties.
• The developed MMA significantly advances the bandwidth capabilities of state-of-the-art metamaterial absorbers.
• This work paves the way for developing ultrabroadband metamaterial devices applicable to various wave systems.