Research of the transmission spectra of photonic crystal waveguide with layered composite medium cylinder

The transmission property of the two-dimension photonic waveguide after introducing layered composite medium cylinder defect was studied by means of the finite-difference time-domain method when changing the radius and refraction index of the cylinder. The results show that more defect states appear in guided gap with the radius and refractive index of the medium cylinder increasing. Even broader guided gap appears when radius of medium cylinder is close to that of air cylinder. Narrow forbidden gap appears in guided gap with big refraction index of the cylinder. The results are very meaningful for design of 2-D photonic crystal devices.