Nonlinear optical properties of armchair nanotube

The magnitude of the third-order nonlinear polarizability γ of armchair nanotube is theoretically studied. The calculated results for the C70 tube are consistent with those measured by Neher et al. [Opt. Lett. 17, 1491 (1992)]. The static and dynamical magnitudes of γ can be greatly enhanced by increasing the carbon number. When the carbon number is big enough, the major dynamical response peaks with large γ magnitudes are located at the optical frequency ω near the energy gap Eg (i.e., 3ω∼3Eg), and the highest peak magnitude is much larger than that of C70, which is important in practical use.