This paper proposes a new type of THz composite Plastic Photonic Crystal Fiber(THz-PPCF)
the cladding of which consists of two kinds of periodically lined air holes with different diameters
and analyzes its dispersion properties by using the Finite-Difference Time-Domain(FDTD) method.The results show that a low-loss super-flattened dispersion THz-PPCF can be achieved by optimizing the air hole diameters and the lattice constant.