Figure 4
Micro-PL spectra of individual ZnO microcavities, intensity profiles, and variation in the lasing threshold density. (a) Micro-PL spectra of individual ZnO microcavities with the size of 6.15 μm upon different excitation densities of pulsed laser. The inset shows the plot of integrated PL intensity as a function of excitation density, exhibiting the lasing threshold of 0.94 MW/cm2. (b) Intensity profiles calculated for a flat-head tapered nanowire (top) and a highly tapered nanowire (bottom). (c) A plot of lasing threshold density versus individual ZnO microcavity size.