Electronics - Optics - Sensors

Metallic Metasurface: How to Stay Under The Radar?

Researchers from the Chinese Academy of Sciences have prepared all-metallic metasurfaces as wide-angle microwave diffusers.

Schematic of the heat resisting metallic metasurface, showing the electromagnetic scattering in the upper half‐space. Inset illustrates two adjacent elements and the located catenary optical field.

Metallic skin has been widely used in various engineering applications because of its excellent mechanical and physical properties, such as high strength, large flexibility, and good ductility, as well as its high temperature resistance and excellent thermal conductivity. As a typical example, aircraft and ship skins often use metal materials to meet the physical requirements.

In stealth technology however the strong reflection of electromagnetic waves by metal is disadvantageous in order to remain undetected. Though radar scattering signal could be reduced by changing the geometries of objects to guide the reflected wave into other directions, shaping the physical geometry is usually undesired due to other physical constraints, such as the compatibility of aero- and hydrodynamics.

As a type of two-dimensional metamaterials, metasurface has been a topic of considerable interest in recent years. According to generalized Snell’s law, the reflection and transmission electromagnetic wavefronts can be reshaped by the local phase control of the metasurfaces. Recently, various building blocks based on metal-insulator-metal (MIM) structures have been presented. This approach uses the random distribution of local reflection phases of unit cells, which enables diffuse electromagnetic scattering. Consequently, the radar cross section (RCS) would be dramatically reduced.

Infrared emission characterization for the metasurface at room temperature.

A team of researchers from the State Key Laboratory of Optical Technologies on Nano-Fabrication and Micro-Engineering, from the Chinese Academy of Sciences designed an all-metallic metasurface, using high-temperature resistant metal materials.

By optimizing the catenary optical fields and dispersion, broadband and wide-angle diffusion in the microwave band was realized. Unlike previous diffusers, the echo reflection is subtly suppressed, thus minimizing the target RCS. In addition, the structure is compatible with both high temperature and infrared camouflage performance. The authors believe that this approach is expected to provide a surface coating for electromagnetic feature control.

Read more about their findings in their full article on Advanced Materials Technologies.

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