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Quenching

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Definition: the reduction or limitation of an excited-state population, mostly by unwanted effects

Category: physical foundations

How to cite the article; suggest additional literature

The term quenching has many different meanings; this article discusses only the context of fluorescence quenching in lasers, particularly solid-state lasers. In rare-earth-doped or transition-metal-doped gain media (laser crystals or glasses), the lifetime of electronic levels of laser-active ions is sometimes strongly reduced. This quenching can have different origins, such as:

Quenching becomes apparent as a reduction in the decay time and the overall intensity of the fluorescence from quenched electronic states. If the upper laser level for some laser transition is quenched, i.e. the upper-state lifetime is reduced, this can raise the threshold pump power of a laser or reduce the gain of an amplifier. However, quenching processes can also be helpful e.g. when they help to reduce the lower-state lifetime and thus the population of the lower laser level, or to populate the upper laser level via pumping into a higher-lying level. There are lasers for which such quenching processes are essential.

Processes responsible for lifetime quenching often (but not always) create additional fluorescence at other wavelengths. For example, fluorescence may reveal the population of higher-lying levels (→ upconversion fluorescence) or the excitation of other ion species (sometimes present as impurities) via energy transfers. However, it can be difficult to determine whether the observed fluorescence really results from the same process which is responsible for quenching. For example, weak upconversion fluorescence could either be some additional weak effect with negligible influence on the level lifetime, or could indicate strong quenching via upconversion (and be weak only because the quantum efficiency of the upconversion fluorescence is small).

Bibliography

[1]D. L. dexter and J. H. Schulman, “Theory of concentration quenching in inorganic phosphors”, J. Chem. Phys. 22 (6), 1063 (1954)
[2]K. Arai et al., “Aluminium or phosphorus co-doping effects on the fluorescence and structural properties of neodymium-doped silica glass”, J. Appl. Phys. 59 (10), 3430 (1986)
[3]R. Wyatt, “Spectroscopy of rare earth doped fibres”, Proc. SPIE 1171, 54 (1989)
[4]E. Delevaque et al., “Modeling of pair-induced quenching in erbium-doped silicate fibers”, IEEE Photon. Technol. Lett. 5, 73 (1993)
[5]P. Myslinski et al., “Effects of concentration on the performance of erbium-doped fiber amplifiers”, J. Lightwave Technol. 15 (1), 112 (1997)
[6]R. Paschotta, et al., “Lifetime quenching in Yb doped fibers”, Opt. Commun. 136, 375 (1997)
[7]M. Pollnau and S. D. Jackson, “Energy recycling versus lifetime quenching in erbium-doped 3-μm fiber lasers”, IEEE J. Quantum Electron. 38 (2), 162 (2002)

(Suggest additional literature!)

See also: upper-state lifetime, lower-state lifetime, upconversion, fluorescence, clustering, gain media, rare-earth-doped gain media, doping concentration, Spotlight article 2006-09-06
and other articles in the category physical foundations

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