Evolution of whispering gallery modes in Li-doped ZnO hexagonal micro- and nanostructures

Abstract

The investigated materials have great potential for integrated optoelectronic devices. The possibility to integrate them into the same material as optical resonator and light guide opens the door to the fabrication of highly compact devices. The formation of optical cavities in Li-doped ZnO nanostructures was investigated. By means of the vapor-solid method, long micro- and nanostructures with a hexagonal cross-section were grown. These morphologies were favorable for Fabry-Perot and whispering gallery modes to appear. A variety of structures with different sections was studied using mu-photoluminescence in both the transverse electric (TE) and transverse magnetic (TM) polarizations, showing well-pronounced optical resonant modes. The results showed a dominance of whispering gallery modes that were in good agreement with the calculated refractive index. The quality factor (Q) and finesse (F) were estimated, which demonstrated the quality of Li:ZnO structures as optical cavities.