Free-electron laser studies of direct and indirect two-photon absorption in germanium

The two-photon absorption of germanium was observed 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 three orders of magnitude smaller than the direct gap. The indirect-gap threshold position indicates...

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Veröffentlicht in:	Physical review letters 1993-06, Vol.70 (26), p.4146-4149
Hauptverfasser:	TUNCEL, E, STAEHLI, J. L, COLUZZA, C, MARGARITONDO, G, MCKINLEY, J. T, ALBRIDGE, R. G, BARNES, A. V, UEDA, A, YANG, X, TOLK, N. H
Format:	Artikel
Sprache:	eng
Schlagworte:	Condensed matter: electronic structure, electrical, magnetic, and optical properties Exact sciences and technology Infrared and raman spectra and scattering Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation Physics
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Zusammenfassung:	The two-photon absorption of germanium was observed 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 three 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.
ISSN:	0031-9007 1079-7114
DOI:	10.1103/physrevlett.70.4146