Revealing Excitonic and Electron Hole Plasma States in Stimulated Emission of Single Cs Pb Br 3 Nanowires at Room Temperature

Nanostructured lead halide perovskites have received extensive attention due to their potential applications in integrated photonics. Despite many successful realizations of nanoscale coherent-light sources from lead halide perovskites, the role and interplay between excitonic and electron-hole plasma (EHP) states in the stimulated-emission process are not demonstrated yet. In this work, the carrier behavior and dynamics of the stimulated emission in ${\mathrm{Cs}\mathrm{Pb}\mathrm{Br}}_{3}$ single nanowires are studied with a streak camera under power-dependent one-photon and two-photon excitation at room temperature. A redshift of the lasing gain profile with increasing excitation fluence is observed, suggesting the transition from the excitonic state to EHP state that is responsible for the lasing. Whereas, a blueshift of the gain profile with time decay represents the opposite direction of the former process. Moreover, the individual lasing modes show a blueshift as excitation fluence increases and a redshift as time elapses, due to the carrier-density dependence of the refractive index. This study could provide a comprehensive and deeper understanding of the carrier-density-driven stimulated-emission dynamics in lead halide nanowires and extend their applications in integrated photonics.