In this study, we focus on the analysis of one-dimensional photonic crystal with symmetric double defect. Using the transfer matrix method (TMM), the properties of defect modes including degeneracy and splitting, can be analyzed in detail. It is found that such properties are mainly depending on symmetry and spatial interval of defects. The results show that the degeneracy of defect modes occurs in two defects separate to each other. And defect modes split when two defects close to each other. The results have potential applications in photonic integration and fiber optic sensor.
Using 4×4 transfer matrix method, we investigated the transmission properties of defect mode in one-dimensional photonic crystal. The system can be transformed to be biaxial photonic crystal under one-way stress. It is found that the transmission properties of defect mode are critically depending on the numbers of dielectric layers and degree of asymmetry. For the system without stress, in the case of system with mirror symmetry, the defect mode is appearing gradually and its peak wavelength always keeps stable with the numbers of dielectric layers increasing, and its corresponding transmittance will be sharply decrease from a constant to zero at the same time. In the case of asymmetry, the defect mode is appearing gradually and its peak wavelength still keeps stable with the asymmetric degree continuously growth. Meanwhile, its transmittance exist an evolution from increase to decrease in this progress, and the maximum transmittance can be obtained at Δ<i>m</i>=0 . After applying a fixed one-way stress on the system, the single defect mode will be split into Left-side defect mode (LDM) and Right-side defect mode (RDM). In the case of system with mirror symmetry, the two defect modes are appearing gradually and their peak wavelength always keep constant with the numbers of dielectric layers increasing, respectively, and their corresponding transmittance decrease asynchronously from a constant to zero. In the case of asymmetry, the peak wavelengths of LDM and RDM are being a constant with the changing of asymmetric degree and their corresponding transmittance are synchronously increasing or decreasing with the continuously increasing of asymmetric degree. Particularly, the maximum transmittance of defect mode also can be obtained at Δ<i>m</i>=0 . This study provided a theoretical guidance for the best choice of numbers of dielectric layers to design a pressure sensor.