Abstract: To achieve the superior filtering characteristics of one-dimensional photonic crystal, the gradient refractive index of defect layer is introduced to inhibit certain frequency of electromagnetic wave and get the photonic band gap. Maxwell's equations were solved strictly with the finite difference time domain (FDTD) method. Discuss the corresponding transmission spectrum when changes in the refractive index of defect layer are parabolic. And analysis the impact of the refractive index ratio, thickness ratio and the cycle number of periodic dielectric layer on the filtering characteristics. Research shows that defect layer with gradient index of the one-dimensional photonic crystal has a wider bandwidth when we increase the refractive index ratio; changing the thickness ratio can affect position of the transmission peak; changing the periodic number, may influence the transmittance. Results of this study have some reference values to improve the performance of photonic crystal filters.

Key words: one-dimensional photonic crystal; filtering characteristics; gradient refractive index of defect layer; refractive index ratio; thickness ratio; periodic number