High‐Power Single‐Quantum‐Well 376 nm Ultraviolet A Laser with Low‐Threshold Current Density

III‐nitride materials have shown promising properties for laser diodes (LDs) due to its direct bandgap, broad wavelength tunability, and compatibility with high‐quality epitaxial growth. However, extending LD operation toward shorter ultraviolet A (UV‐A) wavelengths remains challenging due to the large lattice mismatch between AlN and GaN. In this work, we utilized GaN waveguide (WG) instead of conventional AlGaN WG layer to reduce alloy‐scattering loss and strain while maintaining sufficient refractive‐index contrast for optical confinement. In addition, a single‐quantum‐well (SQW) active region is adopted to mitigate cumulative quantum‐confined Stark effect and carrier‐distribution imbalance, aiming to lower the threshold current density while preserving high slope efficiency (SE). The fabricated device showed a maximum output power of 2.36 W achieved with 750 µm cavity length devices. The lasing wavelength is 375.76 nm with a narrow full width half maximum (FWHM) of 0.42 nm. This design demonstrated a SE of 822.9 mW/A and a threshold current density of 5.89 kA/cm 2 . These results highlight the potential of the GaN WG and SQW design for high‐power, low‐threshold UV‐A LDs.