Multi-photon-pumped stimulated emission from ZnO nanowires: A time-resolved study

In this work, we study temporal evolution of multi-photon-pumped stimulated emission from ZnO nanowires. In addition to second harmonic generation, ultraviolet stimulated emission is observed in ZnO nanowires under femtosecond pulse excitation at 800 nm. Sharp emission peaks appear when excitation flux reaches a threshold of 80 mJ/cm2, which can be interpreted as lasing action in self-formed nanowire microcavities. Temporal evolution of the emission captured by Kerr shutter technique shows strong excitation-power dependence. The dynamic trace of stimulated emission exhibits a fast decay with a lifetime about 4.5 ps at intermediate excitation (∼100 mJ/cm2) and a lifetime about 2 ps at high excitation (>160 mJ/cm2). The difference in the lifetime can be attributed to different gain mechanisms related to excitonic interaction and electron-hole plasma, respectively.

► The ultraviolet stimulated emission was observed from ZnO nanowires under femtosecond pulse excitation. ► We show the results of time-resolved PL study on the observed MPA-pumped stimulated emission from ZnO nanowires. ► The stimulated emission should be contributed by the excitonic emission processes and electron-hole plasma processes.