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Proceedings Paper

Ultrafast polarization dynamics in optically excited biased quantum wells
Author(s): Dmitry Turchinovich; Boris S. Monozon; Martin Koch; Sandra Lahmann; Uwe Rossow; Andreas Hangleiter; Peter Uhd Jepsen
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Paper Abstract

We observe ultrafast polarization dynamics in strongly internally biased InGaN/GaN multiple quantum wells during intense femtosecond optical excitation by means of time-resolved detection of THz emission, correlated with time-integrated photoluminescence measurements. We demonstrate that in the case of strong enough excitation the built-in bias field (on the order of MV/cm) can be completely screened by the carriers excited into spatially separated states. This ultrafast screening of the initial bias field across the quantum well leads to dynamical modification of the band structure of the sample, and consequently to dynamical modification of the optical absorption coefficient within the duration of the excitation pulse. We show that such an optically induced dynamical screening of the biased quantum well can be described in terms of discharging of a nano-scale capacitor with a femtosecond laser pulse. The electrostatic energy stored in the capacitor is released via THz emission. A realistic quantum-mechanical model of the temporal evolution of the polarization inside the quantum wells shows that due to its nonlinearity such a process may lead to emission of a THz pulse with bandwidth significantly exceeding that of the excitation pulse.

Paper Details

Date Published: 8 April 2004
PDF: 8 pages
Proc. SPIE 5354, Terahertz and Gigahertz Electronics and Photonics III, (8 April 2004); doi: 10.1117/12.537783
Show Author Affiliations
Dmitry Turchinovich, Univ. Freiburg (Germany)
Boris S. Monozon, State Marine Technical Univ. (Russia)
Martin Koch, Technische Univ. Braunschweig (Germany)
Sandra Lahmann, Technische Univ. Braunschweig (Germany)
Uwe Rossow, Technische Univ. Braunschweig (Germany)
Andreas Hangleiter, Technische Univ. Braunschweig (Germany)
Peter Uhd Jepsen, Univ. Freiburg (Germany)


Published in SPIE Proceedings Vol. 5354:
Terahertz and Gigahertz Electronics and Photonics III
R. Jennifer Hwu, Editor(s)

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