Size-dependent whispering gallery modes in Au-coated ZnO microrods

We investigated the structural and optical properties of nanoparticle-assisted pulsed laser-deposited ZnO microrods and Au-coated ZnO microrods grown on Si substrate. Our present study indicates that Au-coated ZnO microrods exhibit whispering gallery modes (WGM) in the near band edge region with significant splitting into two branches. Moreover, the WGMs exhibited blue shift with decrease in rod size. We found that the modes are well split in Au coated ZnO rods when compared with as-grown rods, resulted from the plasmon enhancement of WGM modes. We also found that the Au-coated ZnO was stable in the ambient when compared with uncoated ZnO. WGM resonance from the exciton related emission, the enhancement in WGMs, and stability in the ambient condition of the Au-coated ZnO microrods suggest great potential for small-volume devices and microlasers.