Publication

Free-Electron Laser Studies of Direct and Indirect 2-Photon Absorption in Germanium

Giorgio Margaritondo, Jean-Louis Staehli
1993
Journal Articles

Abstract

We succeeded in observing the two-photon absorption of germanium for both the direct and the indirect gaps, using the Vanderbilt free-electron laser. The two-photon absorption for the indirect gap was found to be 3 orders of magnitude smaller than the direct gap. The indirect-gap threshold position indicates that the two-photon absorption is assisted by an LO phonon, providing a long-delayed positive test of the Bassani-Hassan predictions.

Official source

https://infoscience.epfl.ch/entities/publication/63c1188a-e245-4aee-8f5c-4e0dff60b21a

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Giorgio Margaritondo, Jean-Louis Staehli
1993
Journal Articles

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/63c1188a-e245-4aee-8f5c-4e0dff60b21a

About this result

Related concepts (27)

Band gap

In solid-state physics and solid-state chemistry, a band gap, also called a bandgap or energy gap, is an energy range in a solid where no electronic states exist. In graphs of the electronic band structure of solids, the band gap refers to the energy difference (often expressed in electronvolts) between the top of the valence band and the bottom of the conduction band in insulators and semiconductors. It is the energy required to promote an electron from the valence band to the conduction band.

Magnitude (astronomy)

In astronomy, magnitude is measure of the brightness of an object, usually in a defined passband. An imprecise but systematic determination of the magnitude of objects was introduced in ancient times by Hipparchus. Magnitude values do not have a unit. The scale is logarithmic and defined such that a magnitude 1 star is exactly 100 times brighter than a magnitude 6 star. Thus each step of one magnitude is times brighter than the magnitude 1 higher.

Direct and indirect band gaps

In semiconductor physics, the band gap of a semiconductor can be of two basic types, a direct band gap or an indirect band gap. The minimal-energy state in the conduction band and the maximal-energy state in the valence band are each characterized by a certain crystal momentum (k-vector) in the Brillouin zone. If the k-vectors are different, the material has an "indirect gap". The band gap is called "direct" if the crystal momentum of electrons and holes is the same in both the conduction band and the valence band; an electron can directly emit a photon.

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Free-Electron Laser Studies of Direct and Indirect 2-Photon Absorption in Germanium

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