Saturation of the photoluminescence at few-exciton levels in a single-walled carbon nanotube under ultrafast excitation.
Single air-suspended carbon nanotubes (length 2-5 microm) exhibit high optical quantum efficiency (7-20%) for low intensity resonant pumping. Under ultrafast excitation (150 fs), emission dramatically saturates at very low exciton numbers (2-6), which is attributed to highly efficient exciton-exciton annihilation over micron-length scales. Similar saturation behavior for 4 ps pulse excitation shows nonlinear absorption is not a contributing factor. The absorption cross sections (0.6-1.8x10(-17) cm2/atom) are determined by fitting to a stochastic model for exciton dynamics.
Xiao
Y-F
YF
Department of Physics, Engineering Physics & Astronomy, Queen's University, Kingston, Ontario, K7L 3N6 Canada.
Nhan
T Q
TQ
Wilson
M W B
MW
Fraser
James M
JM