Third-Order Nonlinear Optical Response of Fullerenes as a Function of the Carbon Cage Size (C₆₀ to C₉₆) at 0.532 μm

Abstract

We report the results of our degenerate four-wave-mixing measurements (DFWM) on the fullerene series from C60 to C96 dissolved in CS2. The DFWM measurements were carried out using 70 ps laser pulses at the wavelength of 0.532 μm under the optimized experimental conditions. The second hyperpolarizabilities γ1111 of all these fullerenes were determined to be on the order of 10-31−10-30 esu, and overall they increase smoothly with the carbon cage size except for C70 and C78, which show anomalously larger γ1111 values than those of their neighboring cage sizes we investigated. The number of π-conjugated electrons, geometrical structure, and resonance enhancement are discussed as possible factors responsible for the observed third-order optical nonlinearities of the fullerenes.