A transparent zinc oxide based metamaterial for perfect absorption of long- wavelength and mid-wavelength infrared spectral bands

Abstract

A high absorption capabilities in atmospheric transparency windows lies at mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) region is important for various applications, particularly, for passive thermal cooling and camouflage technology compatible with infrared (IR) lasers. In this paper, we proposed a simple and cost-effective design for a tri-layered metamaterial based on zinc oxide (ZnO) which exhibits almost perfect absorption in both the mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) regions with excellent transmission in the visible range. It consists of a metal-dielectric-metal sandwiched structure with a two-dimensional periodic pattern of gallium doped ZnO circular discs at the top, ZnO in the middle, and an aluminum doped ZnO at the bottom. The proposed metamaterial exhibits almost perfect absorption in both the LWIR (∼ 10 µm) and MWIR (∼ 5 µm) regions, while maintaining excellent transmission (∼ 75%) in the visible region. Further, it also exhibits a better angular (0–50°) insensitivity with respect to the incident angle and to the polarization (TE and TM) of electromagnetic wave. The proposed metamaterial has potential applications in thermal cooling/emission and infrared camouflage technology.