High Beam Quality in Broad Area Lasers via Suppression of Lateral Carrier Accumulation

High power 9xx-nm broad-area lasers with improved beam quality are required for many applications, but the physical limitations remain unclear, especially the relative importance of free-carrier and self-heating effects. Experimental data are, therefore, presented on a series of diagnostic lasers where the lateral carrier profile at the edges of the electrical contacts has been modified via implantation in order to assess its influence on beam quality. We show that carrier accumulation at the edges of the (90-mu m wide) contacts can be eliminated and that as a consequence, near and far field are narrowed and the rate of increase of beam parameter product (BPP) with self-heating reduces by 35%. Overall, the suppression of lateral carrier accumulation allows BPP < 2 mm x mrad to be maintained to 7-W optical output, corresponding to a peak linear brightness of 3.5 W/mm x mrad, comparable with the highest reported values for 90-mu m stripe devices.