Visible emission of single-wall carbon nanotubes formed in micro-channels of zeolite crystals

Emission spectroscopy is performed to study the optical transitions between electronic bands of SWCNs formed in AlPO4−5 (AFI) crystal. Strong visible emission is observed under laser light illumination at room temperature. The emission is excited by the light polarized along the c-axis and its polarization is also along this direction. On the other hand, non-linear emission is observed under the resonant excitation of the lowest absorption band of SWCNs. The emission is excited by the light polarized along the c-axis, but it shows the polarization perpendicular to the c-axis. The polarization character is discussed on the basis of the selection rules of the optical transitions predicted by the full line-group symmetry of SWCNs.