Inter-subband exciton relaxation dynamics in single-walled carbon nanotubes

This work reports the dynamics of photoexcited excitons in single-walled carbon nanotube (SWNTs) using ultrafast pump-probe experiments. Early exciton relaxation from higher levels is concluded in 150 fs, with a time constant of the order of 40 fs. Due to the concentration of oscillator strength induced by confinement in the 1D space, SWNTs are predicted to have very large nonlinear optical absorption. This property in combination with the very fast recovery times measured, makes SWNTs ideal candidates for ultrafast all-optical switching application at frequencies well in excess of 1 THz.