Optically transparent microwave devices, which convey divergent microwave functionalities on optical observation windows, play important roles in the rapidly developing optoelectronic-integration compact systems for next-generation wireless communications, electromagnetic environmental safety, and hyperspectral detection.

However, achieving high-performance transparent microwave devices is still very challenging owing to the limitations of traditional transparent conductive materials. For example, indium tin oxide based devices cannot balance the conflict between high optical transmission and strong electromagnetic shielding due to intrinsic loss, and conventional metal mesh–based transparent devices introduce concentrated stray light spots due to the strong diffraction effect, which generates ghost images and degrades the imaging quality.

In a study published in Photonics Research, Prof. SONG Naitao from the Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP) of the Chinese Academy of Sciences (CAS) proposed a generalized solution for optically transparent anti-diffraction metamaterial absorber.

To be specific, the optically tranaparent metamaterial absorber consisted of tri-layer ITO lossy metasurfaces and an aluminum Thiessen polygon metal mesh (TPMM) reflector. The ITO lossy metasurfaces absorbs broadband microwave, and TPMM prevents microwave penetration. The randomness of TPMM also prevents the concentration of stray light.

It has been validated that Thiessen polygon metal meshes do not degrade modulation transfer functions of an optical system or introduce higher-order aberrations such as astigmatism that damage imaging quality uniformity, but can avoid concentration of stray light.

Experimental results revealed that this hybrid architecture ensures a 10-dB absorption and 10-dB shielding effectiveness over a range of 8–26.5 GHz, and an average optical transparency of 84.3% was maintained over a wavelength range of 400–1200 nm.

Compared with the current state-of-the-art, this work has the unique advantage of anti-diffraction. TPMM is a generalized solution to the anti-diffraction necessity of opto-microwave integration. This work may have a significant impact on optically transparent functional EM devices, multispectral integrated detection systems, and transparent displays.