Nonlinear and ultrafast optical response in single-walled carbon nanotubes

Abstract

We measured third-order nonlinear susceptibility (χ(3)) spectra in semiconducting single-walled carbon nanotubes (SWNTs) by the Z-scan method. |Im χ(3)| is remarkably enhanced under resonant excitation to the lowest interband transition, reaching 4.2 × 10 -6 esu. A comparison of the transient absorption changes evaluated by degenerate and nondegenerate pump-probe measurements suggests that the resonant enhancement of |Im χ(3)| is dominated by a coherent process rather than by incoherent one such as saturation of absorption. © 2005 IOP Publishing Ltd.