Wide-angle camouflage detectors by manipulating emissivity using a non-reciprocal metasurface array

Area of Science:

• Metamaterials
• Optics
• Materials Science

Background:

• Stealth technology, guided missiles, and heat-seeking missiles require camouflage detectors that can operate covertly.
• Kirchhoff's fundamental law dictates that absorption and emission are reciprocal (α(θ) = ε(θ)), limiting detector functionality.
• Existing detectors emit radiation back towards the source, potentially revealing the object's location.

Purpose of the Study:

• To develop a novel camouflage detector capable of independent directional detection and emissivity control.
• To overcome the limitations imposed by Kirchhoff's law for enhanced stealth applications.

Main Methods:

• Utilized a nonreciprocal metasurface array incorporating indium arsenide (InAs), a magneto-optical material.
• Exploited InAs to break Lorentz reciprocity and Kirchhoff's law, achieving nonreciprocal absorption and emission (α(θ) ≠ ε(θ)).
• Designed, optimized, and tested nine metasurfaces operating at various incident angles (+50° to -50°) at a 13 μm wavelength.

Main Results:

• Demonstrated independent manipulation of absorption and emission, with the relation α(θ) = ε(-θ).
• Achieved directional detection and controlled emissivity across a wide angular range (±50°).
• A pixilated array configuration enables full-angle operation.

Conclusions:

• The developed nonreciprocal metasurface array offers a breakthrough in camouflage detector technology.
• This technology enables independent control over radiation detection and emission, enhancing stealth capabilities.
• Potential applications include advanced thermal emitters and solar-harvesting systems.