Design and Spectral Analysis of Short and Medium-Wave Infrared Filter for High Resolution Detectors

The short- and medium-wave infrared filter is a key device in the aerospace optical remote sensing camera. The spectral response of the high-resolution detector is determined by the spectral characteristics of the short- and medium-wave infrared filter. Owing to the gap between the preparation level and theoretical values, the phenomenon of the spectral angle drift or temperature drift occurs, and the mixed superposition of high- and low-frequency spectra is formed in the high-resolution detector, resulting in restoration spectral distortion. This study introduces a design method for a working band of 3.5 μm to 4.1 μm and the development of a short- and medium-wave infrared filter for a high resolution detector. To realize the characteristics of dual band cut-off color separation on the Si substrate (cut-off band wavelength 2.4 μm to 3.35 μm and 4.25 μm to 6.4 μm; transmittance of over 98% in passband wavelength 3.5 μm to 4.1 μm), the film system structure of the F-P band-pass filter is used as the initial structure, which effectively reduces the number of film layers compared with the conventional design concept. The high refractive material of the film is TiO₂ and the low refractive material is SiO₂, to achieve dual band cut-off. The short- and medium-wave infrared filter achieves the design goal and has the characteristics of dual band cut-off and high band transmittance. In the environmental test, the short- and medium-wave infrared filter exhibits significant stability, and the matching degree between the films is appropriate. The short- and medium-wave infrared filter can be applied in some extreme cases.