Ultrathin and broadband metamaterial absorber based on new four L structure in infrared and visible region

Abstract

In this paper, we proposed a broadband and polarization-insensitive metamaterial absorber in infrared and visible region. Our structure composed of three layers, and the remarkable difference is that two materials (InSb and Tin) are used in the top layer simultaneously. The numerical results show that a broadband absorption above 90% from 88.4 to 110.9 THz can be achieved for either transverse electric or magnetic polarization waves due to the effect of using hybrid materials. Moreover, the metamaterial is ultra-thin, having total of 0.3 µm, i.e., λ/10 with respect to the center frequency of the high absorption bands. In addition, the mechanism of high absorption at resonances is discussed based on the surface current and power loss distributions. The power loss distributions between high and low frequency resonant point are distinct. Importantly, the proposed absorber also have a broadband absorption from 639.7 THz to 796.7 THz by adjusting the parameter of the structure and the idea of broadening absorption bandwidth supplies a useful way in THz, infrared, even in optical region. The new “four L” structure absorber has potential application in sensing, energy harvest, integrated photodetectors and so on.