Far-field second-harmonic fingerprint of twinning in single ZnO rods

The third-rank susceptibility tensor that describes the second-harmonic generation changes sign after an inversion operation indicating its sensitivity to twinning structures. Here, we show the far-field scattering patterns of second-harmonic (SH) radiation generated by single twinned and twin-free ZnO rods. The patterns have been successfully correlated with the twinning structures. A finite dipole-wire model has been effectively employed to model the pattern. It indicates that the dark or bright fringes at the 0^∘{} scattering angle originate as a result of the destructive or constructive interference of SH waves emitted from each halves of the twinned or twin-free ZnO rod.