Surface plasmons promoted single-mode polariton lasing in a subwavelength ZnO nanowire

Constrained by the large mode loss, it is a challenge to achieve low threshold lasing in a thin nanowire whispering-gallery-mode (WGM) cavity at room temperature (RT). Here, we demonstrate low threshold single-mode polariton lasing at RT in a thin ZnO nanowire (165 nm in diameter) on Al₂O₃ layer/rough Ag film. Such a structure can compensate the whispering-gallery mode loss and enhance the WGM polariton emission in UV region for subwavelength ZnO nanowires. They are attributed to the strong local electromagnetic field near nanowire induced by Ag film. The polariton lasing is confirmed by the low threshold, narrowing of the linewidth at threshold, nonlinear intensity-power dependence and continous blueshift of the emission. A clear transition from strong coupling regime to weak coupling regime is observed with increasing pump power. This work suggests low-cost and high-performance room-temperature nanolasers or polariton devices achieved in single thin ZnO nanowires.