chapter  8
Radiation Detectors for Infrared Wavelengths
Pages 72

William Herschel (1738-1822) in 1800, the discoverer of the planet

Uranus, got to know the heating effect in sunlight that occurred

beyond the red end of the visible spectrum and understood its

importance (Herschel, 1800). He called the region the thermometric

spectrum, the term infrared (IR) being coined later (Krus et al.,

1962; Liu et al., 2007). The IR-radiation extends from the red

edge of the visible spectrum at ∼0.70 nm to 1 mm (beyond which microwave region commences). The IR is, in general, is divided into

five subregions (Byrnes, 2009), such as (i) near-IR (0.70-1.4 μm),

(ii) short-wavelength IR (SWIR; 1.4-3.0μm), (iii) mid-wavelength IR

(MWIR; 3.0-8.0 μm), (iv) long-wavelength IR (LWIR; 8.0-14.0 μm),

which provides a better penetration through smoke, smog, dust,

water vapor, etc., and (v) very long-wavelength IR (VLWIR; 20.0-

1000.0 μm).