Whispering gallery modes in single triangular ZnO nanorods.

Whispering gallery modes in ZnO nanorods with equilateral triangular cross sections were studied for the first time, to our knowledge. Photoluminescence following excitation with 325 nm radiation was observed at discrete wavelengths and thereby indicated the excitation of whispering gallery modes of triangular ZnO nanorod resonators. These resonances extended over both the visible emission band and the ultraviolet emission band of ZnO. The refractive index of ZnO between 2 eV and 3.2 eV was calculated assuming a "folded" whispering gallery mode and a simple plane-wave model. Our analysis shows that the plane-wave model produces a dispersion curve that agrees well with that of bulk ZnO for large nanorods but shows small deviations when the size of the nanorod resonator approaches the wavelength of the emitted light.