Ultra-strong mode confinement at semishell metal/insulator/semiconductor interface for nanolaser

Abstract Metal/insulator/semiconductor structure, as a typical interface in conventional electrical and optoelectronic devices, can also act as a plasmon-exciton coupling configuration for designing new concept nanophotonic devices, such as plasmon nanolaser, which is promising to play a coherent light source for nanophotonic integration owing to the spatial localization of surface plasmon (SP). Therefore, it is very important to construct a proper configuration and optimize the nanophotonic performance. In this paper, we designed the Al-semishell structure on ZnO nanorod with SiO2 insulator layer, and further realized plasmonic lasing with high performance. The simulation demonstrated a small effective mode area and high effective index of the semishell ZnO nanocavity with a thickness-optimized dielectric layer, while the experiment revealed plasmon lasing with low threshold (27 MW/cm2) and high quality factor (Q = 485), due to the ultra-strong optical confinement. What's more, the plasmon-exciton coupling mechanism of the plasmonic lasing was further investigated through systematically analyzing about lasing mode shift, as well as temperature-dependent and time-resolved photoluminescence (PL). Quite different from electron-hole plasma (EHP) effect in photonic nanolaser from bare ZnO, the weak dependence of temperature on the PL decay life in semishell ZnO plasmonic nanolaser also reveals the coupling of SP-exciton which accelerates the temporal response under direct laser modulation. The presented results create the possibility of highly integrated coherent light sources operating at extremely high speeds.