Ultrafast absorptive and refractive nonlinearities in multiwalled carbon nanotube films

By using femtosecond laser pulses at a wavelength range from 720 to 780 nm, we have observed absorptive and refractive nonlinearities in a film of multiwalled carbon nanotubes grown mainly along the direction perpendicular to the surface of quartz substrate. The z-scans show that both absorptive and refractive nonlinearities are of negative and cubic nature in the laser irradiance range from a few to 300 GW/cm(2). The magnitude of the third-order nonlinear susceptibility, chi((3)), is of an order of 10(-11) esu. The degenerate pump-probe measurement reveals a relaxation time of similar to2 ps. (C) 2004 American Institute of Physics.