Designing a Multi-Periodic Photonic Crystal with Adjustable Transmission Peak for Optical Filter Applications

This paper deals with the effect of adding a TiO2 thin film as a planar defect to a one-dimensional photonic crystal (PC) consisting of [Si/SiO2] stacks. Theoretical calculations were carried out based on the 2×2 transfer matrix method (TMM) using MATLAB software in order to engineer the photonic band gap (PBG). The defect was considered as a variation in the refractive index, so that its presence in the structure leads to the breaking of the symmetry, creating a transmission peak (TP) in the forbidden band. In addition, the amplitude and location of TP can be shifted by changing physical parameters such as the functional wavelength range, thickness of layers, defect layer thickness, and angle of incidence. The results demonstrate that it is possible to arbitrarily engineer the transmission spectrum by changing the aforementioned parameters. Finally, two gaps are induced in the visible and infrared wavelength bands using an innovative and relatively symmetric structure. Through simple calculations, the location of the TPs can be appropriately engineered and adjusted. Importantly, [Si/SiO2]3/TiO2/[Si/SiO2]3/Si3N4 PC structure with three adjustable TPs is designed, which can be used for band pass filter applications.