Ultra-broadband long-wavelength infrared metamaterial absorber based on hybrid structure of holes and pillars

In this article, we propose a novel ultra-wideband, polarization-independent and wide-angle metamaterial absorber for the long-wave infrared region (8~14μm). The topology in this design is obtained by directly covering the surface of photoresist discs with a dielectric-metal-dielectric film, where the substrate supporting discs is a metal ground plane. The topology period is only 1.29 μm and the metamaterial absorber thickness is 1.305 μm. The broadband absorption of the entire long-wave infrared region mainly comes from resonance absorption at two wavelengths of 8.92 μm and 12.4 μm, and these two resonance absorptions are generated at different positions of the topology. The peak absorptions of the metamaterial absorber at 8.92 μm and 12.4 μm are 93.7% and 98.5%, respectively, and the average absorption in the infrared region of 8 to 14 microns is 91.6%. We calculate that the average absorption of the metamaterial absorber for TE mode still exceeds 85% up to an incident angle of 40°. However, for the TM mode, as the incident angle increases, the absorption increases. When the incident angle is 40°, the average absorption exceeds 95%. This metamaterial absorber with high performances in both bandwidth and absorptivity shows a promising prospect in applications such as thermal emitters, thermal coolers, and microbolometers.