Question

Give three common IR windows materials as exampples and state their applicable wavenumber ranges and samples

Answer 1

COMMON IR WINDOWS MATERIALS:

• SILICON: is used at operations in the NIR or MW spectral band and because of its low density, it is used for low weith systems. It's applied for FLIR and thermal imagining mainly and as products of this material there are lenses, beamsplitters, prisms, optical filters. Its wavenumber range is from 1.2 to 7 μm.
• GERMANIUM: Its wavenumber is 2 to 14 μm (about 45 °C) and its absortion increases when hotter it gets. For the designing of lenses is preferred Geramanium because its high index of refraction. It also blocks UV light in a given wavenumber. It is chemically inert, hard and brittle and it tends to fracture. It is applied in FLIR, FTIR and analytical instruments. Products: aspheric lenses, binary diffractive lenses, optical filters, windows
• SODIUM CHLORIDE: this is a very common material which needs protection from water because it's highly water-soluble and transmits from UV to the far IR with a wavenumber range of 0.23 to 12 μm. It's applied for FTIR spectroscopy, lens protectors for CO₂ laser systems, laser systems and analytical instruments. Products: windows, prisms, laser lens protectors.