NW lasers utilizing II–VI compounds, e.g., ZnO18–24 and CdS,25–27 III–V compounds, e.g., GaAs and GaSb,28,29 and their ternary alloys, e.g., CdSSe and InGaAs,30,31 have been demonstrated. Recently, III-nitride NW-based lasers32–48 have attracted a great deal of interest. The direct bandgap III-nitrides (AlN, GaN, and InN) and their ternary and quaternary alloys exhibit many unique properties including relatively large oscillator strength,49,50 large exciton binding energy,51 low surface state densities,52 large band offset, and robust spin coherence.53 In particular, owing to the large exciton binding energy ( at room temperature), GaN materials can have excitonic effects up to room temperature, which could be exploited to realize polariton lasers.54 More importantly, III-nitride NW lasers can potentially cover a broad spectral range from the deep UV (6.2 eV for AlN) to the near-infrared (0.7 eV for InN) regime, as illustrated in Fig. 1. Therefore, III-nitride NW lasers grown on Si substrate will also enable many potential applications in optical information processing and quantum computing.