Enhancements of third-order nonlinear optical response in the triplet excited state of finite open single-walled carbon nanotubes

Abstract

Spin multiplicity enhancements of third-order nonlinear polarizabilities have been investigated at the excited state for finite single-walled carbon nanotubes (5,0) and (6,0) in terms of the time-dependent density functional theory combined with the sum-over-states method. The time-dependent density functional theory at the B3LYP/3-21G level is employed to calculate the transition moments and the excited state energies of optimized tubes. The obtained results show that the third-order polarizabilities of γ at the excited triplet state are enhanced about from 2 to 3 orders of magnitude and the estimated third-order optical susceptibility of χ(3) is as large as 10−8 esu magnitude order. The electron transitions among the three triplet states make significant contributions to third-order polarizabilities of the (5,0) nanotube, and the electron transition between the two triplet states makes main the contribution to those of the (6,0) nanotube.