Optical limiting of C 60 , C 60 charge-transfer complexes, and higher fullerenes from 532 to 750 nm

The wavelength-dependence of optical limiting in the reverse saturable absorber C<SUB>60</SUB> has been studied in detail over a large spectral range and compared to that of two phthalocyanines. The reverse saturable absorption of C<SUB>60</SUB> is found to increase at wavelengths longer than the standardly measured 532 nm. The optical limiting data have been analyzed in terms of the dynamical population rate equations to obtain the excited state absorption cross-sections. The computational effort of the analysis is greatly reduced by a semi-analytic solution to the rate equations that we have developed. We have also demonstrated that the spectral window for optical limiting of fullerenes can be increased to include longer wavelengths at which C<SUB>60</SUB> is transparent. Both a C<SUB>60</SUB> charge-transfer complex and C<SUB>76</SUB> have been shown to exhibit strong reverse saturable absorption at long wavelengths.

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