Third-order optical nonlinearities of chiral graphene tubules

The third-order optical nonlinearities, characterized by the second-order hyperpolarizabilities γ, of chiral graphene tubules are studied. The average contribution η of one carbon atom to the third-order optical nonlinearity of each chiral graphene tubule is calculated and compared with that of a well characterized polyenic polymer. It is found that the smaller the diameter of a chiral graphene tubule, the larger the average contribution η; the metallic chiral graphene tubule favors larger γ values; chiral graphene tubules can compete with the conducting polymer achieving a large γ value which is needed for photonic applications.