Development of Bandpass Filters with Wide Cutoff and High Steepness in Long-wave Infrared

Development of Bandpass Filters with Wide Cutoff and High Steepness in Long-wave Infrared

Citation

任开发 (Ren Kaifa). 长波红外宽截止高陡度带通滤光片的研制 (Development of Bandpass Filters with Wide Cutoff and High Steepness in Long-wave Infrared). 硕士学位论文 (Master's thesis), 长春理工大学 (Changchun University of Science and Technology), 二〇二四年五月 (May 2024).

Keywords

  • 长波红外 / Long-wave infrared / LWIR
  • 宽截止 / Wide cutoff
  • 高陡度 / High steepness
  • 带通滤光片 / Bandpass filter
  • 红外探测 / Infrared detection
  • 透过率 / Transmittance
  • 截止度 / Cutoff / Rejection
  • 杂散光 / Stray light
  • 系统灵敏度 / System sensitivity
  • 噪声 / Noise
  • 锗 / Germanium / Ge
  • 硫化锌 / Zinc sulfide / ZnS
  • 光学薄膜 / Optical thin film
  • 膜系设计 / Film system design
  • 机械掩模法 / Mechanical mask method
  • 真空镀膜 / Vacuum coating
  • 电子枪蒸发 / Electron gun evaporation
  • 电阻热蒸发 / Resistance thermal evaporation
  • 金属化膜 / Metallization film
  • 焊接 / Welding
  • 光谱测试 / Spectral testing
  • 膜厚误差 / Film thickness error
  • 边缘金属化 / Edge metallization
  • 真空封装 / Vacuum packaging
  • 膜层应力 / Film stress
  • 环境测试 / Environmental testing
  • 空心阴极霍尔离子源 / Hollow cathode Hall ion source
  • 晶振膜厚控制仪 / Quartz crystal microbalance / QCM

Brief

This master's thesis focuses on the research and development of a long-wave infrared bandpass filter with a wide cutoff and high steepness, aiming for high transmittance in the 10-11μm range and significant out-of-band rejection for applications in infrared detection systems.

Summary

This article by Ren Kaifa details the research and development of a long-wave infrared (LWIR) bandpass filter designed for infrared detectors. The research covers the design of the optical thin film structure using Ge and ZnS materials on a Ge substrate, its fabrication using a mechanical mask method and vacuum coating, and the development of a metallization film for welding and packaging. Key achievements include achieving high average transmittance (94.3%) in the 10-11μm range with low ripple (1.6%) and high cutoff (average transmittance < 0.1% in the 4-9.5μm and 11.5-16μm ranges). The study also addressed challenges such as film thickness errors through modeling and correction and optimized the metallization process for reliable welding. The fabricated filter successfully passed various environmental tests.

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