Silicon window and germanium window are the most commonly used infrared (IR) windows, the best working wavelength of silicon window is 3-5um, the best working wavelength of germanium window is 2-14um, it is one of the best substrates for filters.
Si windows are a popular product for applications in the 1.2 - 7µm spectral range, and silicon's low density (half that of germanium or zinc selenide) makes it ideal for weight-sensitive applications, especially those between 3- applications between the 5µm range.
It has a density of 2.329 g/cm3 and a Knoop hardness of 1150, so it is harder and less brittle than germanium.
Germanium has good thermal conductivity and high extra-core hardness and strength, and germanium windows are often used in infrared systems that require higher strength.
Due to the high refractive index of germanium windows, an anti-reflection (AR) coating is usually required to improve the transparency of germanium windows. The common wavelengths of germanium windows are: 3~12um or 8~12um.
The transmission characteristics of germanium are extremely sensitive to temperature changes. The higher the temperature, the lower the transmittance. The optimal operating temperature of germanium windows is <100 °C.
The hardness of germanium windows is higher than that of magnesium fluoride windows, and germanium windows can be used in optoelectronics, infrared thermal imaging cameras, infrared laser systems, infrared optical instruments, infrared optics and other fields.
We can customize germanium (Ge) optical windows with different sizes and thicknesses as required, such as germanium (Ge) wafers, square substrates and cylinders, or shapes such as punched holes.
Typical applications for germanium windows include thermal imaging, the material can be used as front optics, and its refractive index allows germanium to be used in wide-angle lenses and microscopes.
In addition, germanium window components can be used with other analytical instruments in FLIR (Forward Looking Infrared) and FTIR (Fourier Transform Infrared) spectroscopy systems.
Germanium has a transmittance of over 45%⁰ between 2-14µm and 45µm, but propagation slows down at 100°C and then faster above 200°C, where exposure to higher temperatures can lead to catastrophic failure of the material.
Therefore germanium windows are not suitable for use in these conditions, in addition, if weight is an issue, the relatively high density of germanium windows should be considered, germanium has a hardness of HK780, which is slightly higher than that of gallium arsenide with similar mechanical properties.
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