Sub-250 nm low-threshold deep-ultraviolet AlGaN-based heterostructure laser employing HfO2/SiO2 dielectric mirrors

We report a sub-250-nm, optically pumped, deep-ultraviolet laser using an AlxGa1−xN-based multi-quantum-well structure grown on a bulk Al-polar c-plane AlN substrate. TE-polarization-dominant lasing action was observed at room temperature with a threshold pumping power density of 250 kW/cm2. After employing high-reflectivity SiO2/HfO2 dielectric mirrors on both facets, the threshold pumping power density was further reduced to 180 kW/cm2. The internal loss and threshold modal gain can be calculated as 2 cm−1 and 10.9 cm−1, respectively.