GaN-based vertical-cavity surface-emitting lasers (VCSELs) are promising for displays, sensing and optical communication, but improving efficiency remains challenging. Researchers have now shown that “cavity tuning,” which controls resonance wavelength, strongly affects laser performance. By analyzing variations across a VCSEL wafer, the team identified optimal mirror loss conditions and extracted device parameters. Their approach achieved 26.4% wall plug efficiency, offering guidance for next-generation high-efficiency visible-light semiconductor lasers.