Broadband ultra-thin Long-Wave InfraRed metamaterial absorber based on trapezoidal pyramid array

Abstract

The ultra-thin absorber in the long-wave infrared band plays an important role in imaging, sensor, and energy collection. Various perfect absorbers in the long wave infrared band have been designed, however, the absorption bandwidth and structural thickness still limit their application. Here, we propose an ultra-thin perfect absorber composed of a periodic Ti trapezoidal pyramid array, on GaAs dielectric spacer layer, with Ti reflection substrate. Due to the excitation of propagating surface plasmon resonance and local surface plasmon resonance, the average absorptivity about 93.6% in the 8–15 μm band is obtained, which is insensitive to the polarization angle and incidence angle. The resonance characteristics of the structure are studied through the electrostatic theory, and the broadband absorption properties for varied geometric parameters are analyzed using the multipole decomposition method. Meanwhile, we achieved the absorptivity more than 90% at 9.1–17.1 μm by changing the dielectric spacer layer structure of the absorber, and the average absorptivity is 92.1%.