Optically pumped ultraviolet lasing from nitride nanopillars at room temperature

A vertical cavity structure composing of an in situ grown bottom $AlxGa1−xN/AlyGa1−yN$ distributed Bragg reflector and a top $SiO2/HfO2$ dielectric mirror for ultraviolet (UV) emission has been demonstrated. Close-packed nanopillars with diameters of around 500 nm have been achieved by the route of nanosphere lithography combined with inductively-coupled plasma etching. Optically-pumped UV lasing at a wavelength of 343.7 nm (3.608 eV) was observed at room temperature, with a threshold excitation density of $0.52MW/cm2$⁠. The mechanism of the lasing action is discussed in detail. Our investigation indicates promising possibilities in nitride-based resonant cavity devices, particularly toward realizing the UV nitride-based vertical-cavity surface-emitting laser.