Continuous wave lasing from individual GaAs-AlGaAs core-shell nanowires

We demonstrate single-mode continuous wave (cw) lasing from individual GaAs-AlGaAs core-shell nanowires (NWs) subject to optical excitation. By comparing the s-shaped input-output characteristics of cw-excited NW lasers with those obtained under pulsed excitation at 4 K, we observe a ∼4× lower equivalent pump power for cw-excitation and a lower minimum lasing linewidth of ∼200 μeV, indicative of the steady-state excitation conditions that result in improved temporal coherence of the emission. Analysis of the NW cavity length dependence of the mode characteristics reveals a clear inverse scaling behavior, with the spacing of Fabry–Perot modes corresponding to a group refractive index of ∼8. Remarkably, when subject to cw excitation heating of the NW-lasers is found to be negligible, as verified by a constant lasing linewidth as well as the absence of red-shifted lasing peak emission at high excitation levels.