Design and Optimization of Novel Optical Low Pass Filters of a 1D-Photonic Crystal Using TiO2/ SiO2 Thin Films

Two novel optical low pass filters are designed, which act as an infrared shield film. The device blocks infrared light and passes only light composed of short wavelengths. The 1D photonic crystal is formed from alternate layers of optical thin films consisting of high (TiO2 material) and low (SiO2 material) refractive indices. The first Filter consists of three laminated films where the first laminated film has an optical film thickness greater than the optical film thickness of the second. A third laminate is interposed between the two laminates that has an optical film thickness less than the first laminate and greater than the second laminate to suppress the ripples in the stop band of the infrared region. The second filter composed of two laminates where first laminated film has an optical film thickness less than the optical film thickness of the second. Modeling these crystals has been carried out using the transfer matrix method (TMM). In addition, the designs have been optimized using an open source program for the design, optimization and synthesis of optical filters (Openfilters). Transmission greater than 93% in the visible region and reflection greater than 98% in the infrared region has been obtained.