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Proceedings Paper

Femtosecond nonlinearity due to virtual excitation in thick bulk GaAs
Author(s): D. S. Kim
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Paper Abstract

We performed femtosecond degenerate four-wave mixing (FWM) experiments at 10 K and at relatively low intensity (100 fs, 0.1 nJ per pulse focused into 200 micron spot) in thick GaAs (500 micron), exciting completely below the band gap (up to 200 meV) where no absorption occurs (Fig. 1a). We found rather strong FWM signal (much stronger than the resonant excitonic signal of etched GaAs or GaAs quantum wells of ∼1 micron thickness) even though no real population is created. Most interesting observations we made are summarized as follows:

(1) The time-integrated (TI) FWM signal always peaks at negative time delay (Fig. 1b).

(2) The signal decreases rapidly as the detuning increases, approximately as (detuning)-6 (Fig. 2a).

(3) There exists very fast pump-probe signal even when the laser is tuned completely below the band gap (Fig. 2b).

To understand our results, we performed first principle calculations. It is shown that virtual excitation is responsible for the observed signal.

Paper Details

Date Published: 1 September 1996
PDF: 2 pages
Proc. SPIE 2778, 17th Congress of the International Commission for Optics: Optics for Science and New Technology, 2778CB (1 September 1996); doi: 10.1117/12.2316132
Show Author Affiliations
D. S. Kim, Seoul National Univ. (Korea, Republic of)

Published in SPIE Proceedings Vol. 2778:
17th Congress of the International Commission for Optics: Optics for Science and New Technology
Joon-Sung Chang; Jai-Hyung Lee; ChangHee Nam, Editor(s)

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