Ultraviolet Lasing Using Individual GaN Nanobelts

It is crucial to realize gallium nitride (GaN) ultraviolet nanolasing to cater the needs of on-chip integration and optical interconnection, quantum information processing, and high-density storage. The key challenge is preparing freestanding high-crystal quality GaN micro/nanostructures with a controllable structure to realize single-mode ultraviolet nanolasing with a low threshold. Here, a freestanding GaN nanobelt is prepared using the graphically epitaxial lift-offtechnique, and multimode ultraviolet Fabry-Perot lasing is obtained from a single GaN nanobelt on a 300 nm SiO2 spacer layer on a Si substrate. To further reduce optical losses and improve lasing performances, anisotropic KOH polishing is chosen to construct smooth mirrors. After process optimization, the Q value of the lasing is enhanced by about fivefold and the threshold is lowered to 7.76 mu W . By further increasing the KOH polishing time to decrease the size of the microcavity, single-mode ultraviolet Fabry-Perot lasing with a Q value of 1036 has been obtained over a threshold of 9.56 mu W at room temperature, due to the absence of mode competition and group velocity dispersion. Our work has provided an effective and straightforward blueprint for the realization of ultrahigh-performance single/ multimode GaN-based lasing based on freestanding micro/nanostructures.