Second-order optical response of single-walled zinc oxide nanotubes from first principles calculations

► We have investigated NLO properties of ZnO SWNTs by using DFT calculations. ► Both zigzag and chiral ZnO SWNTs exhibit large second order NLO response. ► The NLO polarizabilities originate from transitions from O 2p in VB to Zn 4p in CB.