Room-temperature continuous-wave lasing at 318 nm on a relaxed AlGaN template grown on a sapphire substrate

Continuous-wave (CW) lasing at 318 nm is achieved at 20 °C from an ultraviolet B (UVB) laser diode grown on a relaxed AlGaN template atop a sapphire substrate. The device incorporates a refractive index-guided ridge-waveguide structure, high-reflectivity SiO2/Ta2O5 distributed Bragg reflector mirrors, and junction-down mounting on a polycrystalline AlN submount for enhanced optical confinement and heat dissipation. Under CW operation at 20 °C, the threshold current density and current are 4.3 kA cm−2 and 64 mA, respectively. These results demonstrate stable room-temperature CW lasing in an AlGaN UVB laser diode, likely advancing compact and manufacturable laser sources for medical and industrial applications.