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Nanostructured-based broadband perfect absorbers are of great interest in a wide range of applications, including spectroscopy, energy harvesting, and thermal photonics, etc. Here, a planar square meta-ring of nickel (Ni) is presented, which has the potential to absorb a large operational wavelength starting from 400 nm to 3000 nm. The proposed device model comprises a configuration of three layers with a top and bottom metal of Ni and a middle dielectric layer of aluminium nitride (AlN). The designed square ring metamaterial absorber (SRMMA) can attain an average absorption value of more than 90% over a large waveband from 400-3000 nm. Moreover, it can also maintain its absorption value up to 70% for oblique incident angles for both the wave polarization cases (TE and TM). Furthermore, it also exhibits the polarization-insensitive absorption response under the influence of different polarization angles, which is attributed to the four-fold symmetry in the geometry of the square meta-ring. Furthermore, our SRMMA also reduces fabrication complexity and cost due to its simplified design architecture. These promising features of the proposed SRMMA may have widespread applications in solar energy harvesting, thermal emission, and other optoelectronic devices.

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Terahertz (THz) band has been attracting an enormous reputation due to the paucity of natural materials in this range. Artificially flat thin films, called metasurfaces, plead the research community owing to their unprecedented features to manipulate the scattering properties of electromagnetic (EM) waves. Capitalizing on these unique attributes of the metasurfaces, a wideband polarization converter is investigated for THz frequencies. The proposed metasurface rotates the incoming EM wave into its cross-component over a broad spectral range from 1 THz to 1.75 THz. The designed polarization conversion metasurface (PCM) manifests above 90% efficiency, having a bandwidth of 0.75 THz. This unit cell is also scalable to other operating regimes such as microwave and visible, just by scaling its physical dimensions. This kind of wideband PCM remains prudent for various applications of radar cross-section reduction (RCSR), imaging, communication, etc.

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