  We report on optical pulse-train generation from individual air-suspended
carbon nanotubes under an application of square-wave gate voltages.
Electrostatically-induced carrier accummulation quenches photoluminescence,
while a voltage sign reversal purges those carriers, resetting the nanotubes to
become luminescent temporarily. Frequency domain measurements reveal
photoluminescence recovery with characteristic frequencies that increase with
excitation laser power, showing that photoexcited carriers quench the emission
in a self-limiting manner. Time-resolved measurements directly confirm the
presence of an optical pulse train sychronized to the gate voltage signal, and
flexible control over pulse timing and duration is demonstrated.
