Inverse Design of Ultrathin Metamaterial Absorber

Area of Science:

• Electromagnetic theory
• Materials science
• Computational physics

Background:

• Traditional electromagnetic absorbers often require significant thickness (λ/4), limiting their use in compact devices.
• Metamaterial absorbers (MMAs) offer reduced thickness but typically suffer from reduced performance at oblique incidence angles.
• Achieving both ultrathin profiles and wide-angle, high absorptivity remains a key challenge in electromagnetic absorber design.

Purpose of the Study:

• To develop an efficient inverse design method for ultrathin electromagnetic absorbers.
• To merge the advantages of metamaterial absorbers (thinness) and Salisbury screens (angle insensitivity).
• To optimize absorber structures with minimal computational resources.

Main Methods:

• Adjoint optimization-based inverse design was employed to systematically optimize absorber structures.
• Structures were designed to be as thin as λ/20, significantly reducing material usage and size.
• Performance was evaluated across various incidence angles, and computational efficiency was compared against particle swarm optimization.

Main Results:

• Optimized absorbers achieved over 90% absorption at 7.5 GHz.
• High absorption (>90%) was maintained up to 50° incidence, with significant absorption (~80% at 60°, ~70% at 70°).
• The adjoint method demonstrated a ~98% reduction in computational effort compared to particle swarm optimization.

Conclusions:

• The adjoint optimization framework enables the design of ultrathin, wide-angle electromagnetic absorbers.
• This method significantly improves both absorber performance and design efficiency.
• The findings offer a promising solution for advanced applications in stealth, wireless communications, and quantum computing.