Terahertz bandwidth all-optical modulation and logic using multiexcitons in semiconductor nanocrystals.

Optical pumping of semiconductor nanocrystals with femtosecond pulse sequences was performed in order to modulate multiexciton populations. We show for the first time that control of multiexciton populations produces high speed modulation of stimulated emission. Upon the basis of the speed of multiexcitonic processes in nanocrystals, we show modulation rates approaching 1 THz by virtue of strong quantum confinement effects. Employing femtosecond optical pulse sequences, we demonstrate all-optical logic using these nanocrystals in two forms: an AND gate, and an inverter, a key step toward all optical signal processing.