Triple-broadband infrared metamaterial absorber with polarization-independent and wide-angle absorption

A triple-broadband infrared metamaterial absorber with polarization-independent and wide-angle absorption is proposed by a combination of three different configurations. The absorption of each band exceeds 80% in the three frequency ranges of 142–159 THz, 183–200 THz and 233–245 THz. The 3dB relative bandwidths are 14.5%, 13.1% and 9.9%, respectively. Based on the impedance matching theory, impedances of the absorber are calculated and match to those of the free space in the three absorption regions. To better understand the physical mechanism of the broadband absorption, electric field and surface current distributions of the combined structure are investigated. Multiband absorption mechanism is explained by using the wave-interference theory. Finally, absorption of the triple-broadband absorber at different geometric parameters and incident angles are also discussed for two polarizations. The proposed absorber can be a good candidate for the applications in thermal emission, sensing, photo-detection and solar energy harvesting.