Ultrafast polarization modulation induced by the “virtual excitation” of spin-polarized excitons in quantum wells: Application to all-optical switching.

Autor: Gansen, Eric J., Smirl, Arthur L.
Předmět:
Zdroj: Journal of Applied Physics; 4/15/2004, Vol. 95 Issue 8, p3907-3915, 9p, 2 Diagrams, 11 Graphs
Abstrakt: The operation of an all-optical coherent polarization switch that makes use of spin-polarized virtual excitons in unstrained quantum wells is thoroughly investigated experimentally over a wide range of excitation intensities. The device is shown to exhibit a 415 fs switching time and a contrast ratio of >300:1 at ∼100 K in a thin (40 well) sample. The switching mechanisms are discussed in terms of the circular optical selection rules and the virtual excitation is studied by performing differential measurements for various input polarizations. The polarization state changes induced by the spin-polarized virtual population are measured and their contributions to the switch signal separated using a combination of time-averaged, time-resolved, and spectrally resolved ellipsometric techniques. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]
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