Large nonlinear absorption and refraction coefficients of carbon nanotubes estimated from femtosecond Z-scan measurements

Abstract

Nonlinear transmission of 80 and 140 femtosecond pulsed light with $0.79\hat{I}¼m$ wavelength through single walled carbon nanotubes suspended in water containing sodium dodecyl sulphate is studied. Pulse-width independent saturation absorption and negative cubic nonlinearity are observed, respectively, in open and closed aperture Z-scan experiments. The theoretical expressions derived to analyze the z-dependent transmission in the saturable limit require two photon absorption coefficient ${\hat{I}}_0^2\sim$ $1.4cm/MW$ and a nonlinear index ${\hat{I}}^3\sim -5.5\times 10^{-11}c{m}^2/W$ to fit the data.

10 pages, 2 figures. Accepted and to appear in Applied Physics Letters