A broadband and polarization-insensitive perfect absorber based on a van der Waals material in the mid-infrared regime

A broadband and polarization-insensitive optical absorber based on van der Waals (vdW) material h-BN is proposed in the mid-infrared regime. By utilizing the finite-difference time-domain (FDTD) simulation, the broadband absorption spectrum above 95% is achieved from 6490 to 7295 nm. Moreover, the proposed structure can maintain the excellent performance and broadband absorption in a wide range of incident angles. To illustrate the physical mechanism of proposed absorber, we investigate the magnetic field distributions in the each h-BN structural unit at different wavelengths, and comprehend it with the dispersion relation. Thus, we believe that our research can find some important applications for thermal emitters and photovoltaic devices with outstanding properties working at mid-infrared regime.