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Phys. Rev. B 79, 201306(R) (2009) [4 pages]

Ultrafast nonlinear optical response of photoexcited Ge/SiGe quantum wells: Evidence for a femtosecond transient population inversion

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C. Lange1,*, N. S. Köster1, S. Chatterjee1, H. Sigg2, D. Chrastina3, G. Isella3, H. von Känel3, M. Schäfer4, M. Kira4, and S. W. Koch4
1Faculty of Physics and Material Sciences Center, Philipps-Universität, Renthof 5, D-35032 Marburg, Germany
2Laboratory for Micro and Nanotechnology, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
3Dipartimento di Fisica del Politecnico di Milano, CNISM and L-NESS, Polo di Como, via Anzani 42, I-22100 Como, Italy
4Department of Physics and Material Sciences Center, Philipps University, Renthof 5, D-35032 Marburg, Germany

Received 4 March 2009; revised 28 April 2009; published 19 May 2009

Femtosecond time-resolved pump-probe spectroscopy is used to investigate the ultrafast carrier dynamics of Ge/SiGe quantum wells grown on a Si substrate. Pronounced nonequilibrium effects in the relaxation dynamics of the optically injected carrier distributions are observed and analyzed using a microscopic many-body theory. Transient population inversion and optical gain is obtained on a femtosecond time scale for excitation at energies slightly above the lowest direct quantum-well transition.

© 2009 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevB.79.201306
DOI:
10.1103/PhysRevB.79.201306
PACS:
78.67.De, 78.40.Fy, 78.47.Fg, 78.47.J−

*christoph.lange@physik.uni-marburg.de

 
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