GaN-based high-power laser diodes

We report our recent progress on GaN-based laser diodes (LDs) which will be applied as a light source in high-density optical storage systems. Recently we achieved a lifetime of more than 500 hours under continuous-wave operation with a constant power 20 mW at 25°C using GaN-based LDs with a standard ridge structure. We also report the potential of GaN-based LDs with another structure of a buried-ridge. The far-field pattern of the LDs with a buried-ridge structure strongly depended on the Al content of the AlxGa1−xN burying layer. This dependency showed that the device characteristics change from gain-guiding to refractive index-guiding. The critical point was around x=0.30 of an Al content which corresponds to Δn=0.007 of a lateral index step. It was, therefore, found that the optical transverse mode can be controlled by adjusting the Al content of the AlxGa1−xN burying layer.