Today, IR detectors are widely used for commercial and military applications. The IR region of electromagnetic radiation spans photon wavelengths of 0.7 mm to ~1 mm. The IR region is generally divided into three subregions: near IR (NIR) with a range of 700-1400 nm, mid-wavelength IR (MWIR) with a range of 1400 nm-3 μm, and long-wavelength IR (LWIR) with a range of 3 μm-1 mm. The origins of IR photons are the gases, liquids, and solids that make up the universe. These IR sources can both absorb and emit IR radiation. The dependent relationship of radiation absorption and emission spectra on wavelength helps us identify and evaluate materials in our universe. IR detectors make this valuable information observable to humans through their diverse application in a variety of optical characterization instruments for planetary exploration, space, astrophysics, and atmosphere radiation measurement. IR detection and thermal imaging are currently topics of great interest for both military and commercial applications ranging from night vision, surveillance, driving aids, fire fighting, and various medical applications.
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