Design and Preparation of Medium-Wavelength Infrared Band Pass Combined Filter

Design and Preparation of Medium-Wavelength Infrared Band Pass Combined Filter

Citation

王　航 (WANG Hang), 熊长新 (XIONG Chang-xin), 何光宗 (HE Guang-zong). 组合结构的中波红外带通滤光片研制 (Design and Preparation of Medium-Wavelength Infrared Band Pass Combined Filter) [J]. 光学与光电技术 (Optics & Optoelectronic Technology), 2015, 13(4): 83-86.

Keywords

  • 中波红外 / Medium-wave infrared
  • 带通滤光片 / Bandpass filter
  • 组合结构 / Combination structure
  • 长波通 / Long-wave pass
  • 短波通 / Short-wave pass
  • 截止带 / Rejection band/Cut-off band
  • 透过率 / Transmittance
  • Si 基底 / Si substrate
  • 电子束蒸发 / Electron beam evaporation
  • 离子束辅助沉积 / Ion beam assisted deposition
  • Ge / Germanium
  • ZnS / Zinc sulfide
  • 光学性能 / Optical performance
  • GJB2485 - 95 (Environmental test standard)
  • 热像仪 / Thermal imager
  • 红外光谱仪 / Infrared spectrometer - FTIR
  • 截止波长 / Cut-off wavelength
  • 通带 / Passband

Brief

This article details the research and development of a mid-wave infrared bandpass filter fabricated on a Si substrate using a combination of long-wave pass and short-wave pass films deposited via electron beam evaporation and ion beam assisted deposition, achieving an average transmittance of over 80% in the 3.7-4.2μm range and good out-of-band blocking.

Summary

This article describes the development of a mid-wave infrared bandpass filter by combining long-wave pass and short-wave pass films deposited on a Si substrate using electron beam evaporation and ion beam assisted deposition. The resulting filter achieved an average transmittance above 80% in the 3.7-4.2μm range and good blocking in the 3-3.6μm and 4.3-5μm ranges, and it passed environmental adaptability tests. The use of a combined structure allows for a higher rectangularity and wider passband and rejection band compared to traditional Fabry-Pérot structures. The design involved optimizing the film system using Ge and ZnS as high and low refractive index materials and addressing issues like substrate refractive index mismatch through matching layers. The fabricated filter's performance was close to the theoretical design and met the required specifications.

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