  In this paper, a tunable metamaterial perfect absorber based on vanadium
dioxide (VO2) is designed in the terahertz frequency range. The proposed
structure is simulated by the numerical method of three-dimensional Finite
Difference Time Domain (FDTD). Simulation results show that the absorption
spectrum of the device in the normal incidence of a plane wave light in the
range of 1 THz to 12 THz, has three polarization-insensitive resonance peaks
whose amplitude changes for the different conductivities of VO2 and shifts in a
certain frequency range. This device also having a tolerance of 6 degrees of
incidence angle can provide a relatively stable absorption spectrum.
