Film system Design for shortwavelength pass filter

The principle and calculation method to design shortwavelength pass filters with a concept of equivalent refractive index is presented in this paper. TiO2 was chosen as the material of high refractive index and SiO2as the material of low refractive index based on the principle and method. Periodicity of shortwavelength pass filter at wavelength λ＝950～1150nm was theoretically designed according to the concept of equivalent refractive index. The main film system and the spectrum curve of the shortwavelength pass filterare presented. The design of the film system was corrected since its transmissivity did not meet the requirement at the range of wavelength λ＝750～810nm. The effect of the main processing technology and the film thickness on the optical characteristics of the shortwavelength pass filter is described. As a result of the correction, the best way to make the film system was found. The film system prepared in this way was tested in different environment conditions. The experiment result shows that the specification of this film system can meet the requirement of the design.