Infrared materials produce good transmission in the infrared (IR) spectrum, which spans 0.75 μm to 15µm. Infrared materials are commonly selected for their transmission properties in the NIR (0.75µm – 1µm), SWIR (1µm – 2.7µm), MWIR (3µm – 5µm) or LWIR (8µm – 12µm) spectral sub-regions. The most common IR materials are silicon, germanium, sapphire, zinc sulfide, and zinc selenide.
Silicon has a low density and is ideal for weight-sensitive applications. It is also cost-effective for mid-wave applications. Other properties include:
- Thermal stability
- Low birefringence values
- Excellent environmental durability
Germanium is harder and denser than silicon, so it is useful in applications that require rugged optical components. Additional properties include:
- Highest refractive index among common IR materials
- Lowest optical dispersion among common IR materials
- Effective 50-50 beam splitting without coatings
- Decreased transmission as temperature increases (must be used at temperatures under 100 °C)
Sapphire is an extremely hard and durable material with good transmission across the visible, NIR, SWIR and MWIR ranges. Other properties include:
- Good thermal stability
- High melting point (2,040 °C)
- Low transmitted wave distortion
Zinc Sulfide Properties
Zinc sulfide is a cost-effective infrared material with good transmission from 0.36 μm to 12 μm. Its multispectral version is ideal for applications requiring a single aperture for beam paths in several wavebands.
Zinc Selenide Properties
Zinc selenide has a very low thermal expansion coefficient and exceptional homogeneity across many spectrums. This IR material is a great choice for CO2 lasers, thermometry, and spectroscopy applications.
Effective infrared transmission is important in a variety of applications:
- Defense and aerospace
- Thermal imaging
- FTIR spectroscopy
- Optical gas imaging
Learn More About Infrared Materials & Available Grades