Long-wave infrared absorption measurement of undoped germanium using photothermal common-path interferometry

Germanium is one of the most commonly used materials in the longwave infrared ($\lambda \sim{8 {-} 12}\;\unicode{x00B5}{\rm m}$λ∼8-12µm), but ironically, its absorption coefficient is poorly known in this range. An infrared photothermal common-path interferometry system with a tunable quantum cascad...

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Bibliographic Details
Published in:Applied optics (2004) 2020-04, Vol.59 (11), p.3494
Main Authors: Lee, Yu-Jen, Das, Avijit, Mah, Merlin L, Talghader, Joseph J
Format: Article
Language:English
Subjects:
Absorptivity
Germanium
Infrared absorption
Interferometry
Tunable lasers
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Summary:Germanium is one of the most commonly used materials in the longwave infrared ($\lambda \sim{8 {-} 12}\;\unicode{x00B5}{\rm m}$λ∼8-12µm), but ironically, its absorption coefficient is poorly known in this range. An infrared photothermal common-path interferometry system with a tunable quantum cascade pump laser is used to measure the absorption coefficient of ${ \gt }{99.999}\% $>99.999% pure undoped germanium as a function of wavelengths between 9 and 11 µm, varying between about 0.15 and ${0.45}\;{{\rm cm}^{ - 1}}$0.45cm over this range.
ISSN:1559-128X
2155-3165
DOI:10.1364/AO.390374