Ultra-broadband and polarization-insensitive terahertz metamaterial absorber based on undoped silicon
Z. Xu, Yujie Li, Bin Han, Quan Yuan, Yanan Li, Weiyan He, Junhua Hao, Liang Wu, Jianquan Yao
Abstract
Terahertz (THz) absorbers with high absorptivity across a wide frequency band have attracted considerable interest. In this paper, we present the design of an ultra-broadband THz metamaterial absorber with high absorptivity based on a single-layer square silicon array and a silicon film backed with metallic gold. It is numerically demonstrated that the absorption exceeds 90% covering the frequency range of 0.62-8.75 THz (with an effective absorption bandwidth of 8.13 THz) when the conductivity of semiconductor (undoped silicon) is 600 S/m. Diffraction and impedance-matched induce strong absorption and the corresponding broad bandwidth. The proposed ultra-broadband THz absorber is polarization-insensitive at normal incidence. It can operate over a rather wide range of incidence angle up to 60 degrees for transverse magnetic (TM) terahertz wave. This work provides a way to achieving ultra-broadband terahertz absorption, which is very useful in the development of terahertz imaging, high sensitivity sensors and detection.