Design and fabrication of infrared double half wave filter

The infrared double halfwave filter was traditionally implemented with sixteen λ/4 layers and a low refractive index material as its interval according to the design introduced in Applications Optical Coating written by Mr. Tang Jinfa, Zheng Quan. However, the film prepared by such design tends to crack easily.To solve this problem, a new design for infrared double halfwave filter is presented. A high refractive index material was taken as interval and twelve λ/4 layers was used. Compared to the previous design, it is more economic and timesaving. Detailed technology on how to design and fabricate infrared double halfwave filter is given, and process parameters such as base pressure of chamber, control of temperature and the rate of deposition are described. In the course of deposition, ion source was employed to process substrate and to assist ZnS and Ge evaporation. A satisfactory result was achieved with such design.