Design and Simulation Analysis of Thin Film for Continuously Variable Filter

Continuously variable filter based on Fabry-Perot interference was studied in the paper. A thin film interference signal transmission model whose spectral characteristics are continuously variable with spatial direction was established. According to the design specifications of continuously variable thin film filter with wide band and high dispersion coefficient, and were selected as high and low refractive index materials respectively, the TFCalc thin film design software was used to optimize the design of narrowband filter film by the variable metric method, and the cascade mode of symmetric film stacks with different center wavelengths was used to design broadband cut-off film to broaden the cut-off band. The designed formula has a continuously varying film thickness distribution along the spatial direction of the substrate, so that the center wavelength of the bandpass filter at each position along the spatial direction of the filter is linearly distributed. The designed filter can obtain a spectral gradient of 650-1050nm within the effective working region of 12mm, and the linear dispersion coefficient is 33.33nm/mm. The single-piece integrated multi-channel filtering is realized, which fully meets the requirements of miniaturization, wide working band and high spectral efficiency.