Admittance analysis of broadband omnidirectional near-perfect absorber in epsilon-near-zero mode

In this paper, we propose a broadband omnidirectional near-perfect absorber that transforms light energy into heat. In contrast to previous research on structural metamaterials, this study focuses on light absorption in the epsilon-near-zero (ENZ) layers without any structural patterns. Chromium (Cr) thin films were applied as ENZ layers. Using the admittance method, we found the proper thicknesses of SiO₂ layers to match the incident medium and achieve perfect absorption. Also, the absorber is angular insensitive up to 60^◦. The temperature of the absorber increases from room temperature to 42^◦C, which is 4^◦C higher than the uncoated substrate at 38^◦C, after exposure to sunlight for 20 min.