Design of Optical Thin Film Filter for Sensor Network

Human body detection is very important especially in the countries prone to earthquakes. Fabry-Perot filter as an ideal option in this field needs to be explored. This filter is useful for detection of objects that have temperature around that of the human body. In the presented research, an optical thin film Fabry-Perot filter (FPF) at the wavelength about 8 urn to 14 urn is investigated The important factors on transmission spectrum and the band width of filter are discussed. Additionally structural factors such as layers material and their thickness are explored. Various materials with high and low refractive index are examined by TFCalc3.5 for thin film layers. Germanium (Ge) with the refractive index 4.20 is selected for layer with high refractive index and Silicon Dioxide (SiO₂) with the refractive index 1.46 is selected for low refractive index layer. Our simulation results lead to optimum parameters as: Germanium layer with 196nm thickness and Silicon Dioxide layer with 451 nm thickness. Simulation of proposed filter indicated that the transfer coefficient is more than 90% in desired spectrum. Filter structure can be used on Infrared detectors to improve their resolutions and detection.