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-off technique, and multimode ultraviolet Fabry–Pérot lasing is obtained from a single GaN nanobelt on a 300 nm SiO 2 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 μW. By further increasing the KOH polishing time to decrease the size of the microcavity, single-mode ultraviolet Fabry–Pérot lasing with a Q value of 1036 has been obtained over a threshold of 9.56 μW 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.