Abstract. The nonlinear refractive index n₂ and the two-photon absorption coefficient α₂ are calculated for a bundle of diameter-distributed and aligned single-wall carbon nanotubes. The dispersion of the nanotube circumference length is shown to have important effects on the resonant behaviour of both quantities under consideration, giving rise to a strong broadening, intensity decrease, and `red' shift of the position of the positive and negative resonant peaks in the n₂(ω) and α₂(ω) spectra. It is predicted that a relatively large refractive-index change (~ 1 cm² GW^-1) from a positive to a negative peak value produced by a relatively small variation of pump frequency can be achieved for real samples of carbon nanotubes in the frequency range where they are almost transparent. The results indicate that carbon nanotubes are a promising novel class of nanoscale materials that could be used in practical optical switching applications.

Keywords: Nonlinear-optical properties, carbon nanotubes, fullerenes

Print publication: Issue 4 (July 2001)
Received 26 February 2001, in final form 29 May 2001