Ultraviolet Lasing Using Individual GaN Nanobelts

Abstract

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 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 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.

Directional freezing-induced self-poled piezoelectric nylon 11 aerogels as high-performance mechanical energy harvesters

“…40 Recently, many groups have focussed on the design and fabrication of three-dimensional porous ceramics, polymers and composite-based piezoelectric devices. 12,23,[41][42][43][44][45][46] Porous piezoelectric materials were reported to show high output sensitivity and a higher piezoelectric harvesting gure of merit over dense materials. 47 Previous studies demonstrated that porous materials featuring a lower modulus have improved compression deformation and also the emergence of local stress hot spots improved the output performance.…”