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

Abstract

Nonlinear transmission of 80 and 140 fs pulsed light with 0.79 mu m wavelength through single walled carbon nanotubes suspended in water containing sodium dodecyl sulfate 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 beta(0)similar to 1.4 cm/MW and a nonlinear index gamma similar to-5.5x10(-11) cm(2)/W to fit the data. (c) 2007 American Institute of Physics.