Design a two-gap transmission filter in visible wavelength by one-dimensional photonic crystal

In this paper Si/SiO2 stacks were used to design a one-dimensional photonic crystal for application in visible light filters. In normal mode, transmission spectra has a forbidden transmission region, but by inserting the TiO2 thin film as a defect layer between the stacks, a transmission gap with a width of a few nanometers was created in forbidden band. In addition, with a simple innovation and with the help of a relatively symmetric structure we managed to create two gaps in the band of visible and infrared wavelengths. By simple calculation, the location of the two gaps can be quite engineered and adjustable. It should be noted that in some structures three adjustable gap were created which can have a variety of applications. All calculations have been carried out based on a 2 × 2 transfer matrix method TMM using MATLAB software .