The terahertz (THz) absorption features are theoretically investigated in a symmetric one-dimensional photonic crystal hybridized with a vanadium dioxide (VO2) phase change material (PCM). VO2 is one of the most prominent PCMs whose conductivity increases three orders of magnitude during its phase transition from a semiconducting monoclinic to a metallic tetragonal structure. Here, we utilize this property of VO2 to engineer a tunable THz optical device. Our results show that when the VO2 is in the semiconductor state with low conductivity of 200 S/m, the structure is nearly reflective. However, increasing the VO2 conductivity continuously to the value of 1.5 × 10^5 S/m increases its metallic level further leading to the perfect absorption of the structure. Further increasing the VO2 conductivity to the value of 2 × 10^5 S/m reconfigures it to the fully metallic state so that the absorption peak value remains unit as well. In other words, there is a unit contrast in the absorption levels between two semiconductor and metallic states of VO2 for the proposed structure, which makes it promising for designing tunable nearly reflective and absorbent bifunctionality and optical switching THz devices.
