[60]Fullerene-containing polyurethane films with large ultrafast nonresonant third-order nonlinearity at telecommunication wavelengths.

A significantly enhanced, ultrafast third-order optical nonlinearity at the wavelengths of 1150-1600 nm was demonstrated with cross-linked C60-containing polyurethane films using the Z-scan technique. Good-quality polymer films with a high loading of C60 derivative were obtained by cross-linking of the hydroxyl-containing C60 derivative and a triisocyanate. The positive Kerr coefficient with nonresonant nonlinear refractive index n2 falls in the range of (3.7 +/- 0.80) x 10-4 to (2.0 +/- 0.6) x 10-3 cm2/GW, and the calculated chi(3) and gamma values are up to 9.7 x 10-11 and 9.6 x 10-32 esu at 1550 nm, which are several orders of enhancement in third-order optical nonlinearity over pristine C60 in solution and 1-2 orders of enhancement over recently reported C60 derivatives and conjugated polymers.