Design and Analysis of a Nickel-Coated Polarization-Insensitive Ultra-Wideband Metamaterial Infrared Absorber for Thermal Imaging Applications

A metamaterial absorber (MMA) using a cost-effective nickel material is proposed for infrared region applications. The resonating patch is composed of a metamaterial-based circular resonator with unique fourfold rotationally symmetric curved arms. The cost-effective nickel (Ni) material is utilized for both bottom and top conductive layers, and Rogers RT5880 is used as a dielectric material for the proposed absorber structure. The transmission of electromagnetic radiation is prevented by the bottom-side nickel-based layer. The overall physical size of the proposed unit cell is only 1.7 μm × 1.7 μm × 2.5µm, which corresponds to an ultra-compact electrical size of 0.0916λ0 × 0.0916λ0 × 0.1347λ0. The proposed absorber maintains a high absorptance of ≥90% over an ultra-wide absorption bandwidth of 25.36THz with polarization insensitivity and wide angular stability. It operates from 16.16THz to 41.52THz, corresponding to 7.22 μm to 18.55 μm wavelength range, covering the designated spectrum of the long-wave infrared (LWIR) atmospheric window (8–14 μm) and partly extending into adjacent infrared spectral regions. The absorption bandwidth of 25.36THz corresponds to a relative bandwidth (RBW) of 87.93%. The proposed thermal MMA shows Full Width at Half Maximum (FWHM) of 120%, which is 37.5THz, covering 12.5 to 50THz ultrawide spectrum. The proposed MMA effectively maintains a spectral emissivity of ≥0.90 across its entire functional band, confirming its applicability as an efficient ultra-wideband thermal emitter. Based on the results of this proposed study, the recommended nickel-based polarization-independent infrared metamaterial absorber (IR-MMA) could be an excellent option for thermal imaging, molecular spectroscopy, and stealth technology applications.