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Third-order Optical Nonlinearities of Higher Fullerene and Carbon Nanotube

Recent theoretical and experimental studies on the third-order optical nonlinearities of higher fullerenes including C70, C76, C84, C86, C90, C94 and C96 are briefly reviewed. The extended Su-Schrieffer-Heeger model is introduced and applied to study the third-order optical nonlinearity of chiral carbon nanotubes (CCN), where the average contribution Γ of one carbon atom to the third-order optical nonlinearity of each CCN is calculated and compared with that of a well characterized polyenic polymer. It is found that (i) the smaller the diameter of a CCN, the larger the average contribution Γ; (ii) the metallic CCN favors larger third-order optical nonlinearity than the semiconducting one; (iii) CCN can compete with the conducting polymer achieving a large third-order optical susceptibility. Also the doping effect on the second-order hyperpolarizability of a tubular fullerene is investigated. It is found that the doping effect increases greatly the magnitude of the second-order hyperpolarizability of tubular fullerene.