Experimental studies of GaAs-based broad area diode lasers using highly asymmetric epitaxial structures with high modal gain: finding a path to exceeding 80% conversion efficiency at 25°C

Although continuous wave conversion efficiency at 20W from 9xx-nm broad area lasers (BALs) with 90…100µm stripes has strongly increased, peak efficiency remains 70+/-5%. Recent experimental studies indicate how to potentially overcome this limit. Much higher external differential efficiency is observed at 150…200K than at 25°C, and this helps BALs to reach ~80% conversion efficiency. Studies of spontaneous emission link this improvement to improved carrier density clamping along the resonator. The higher modal gain and lower threshold arising at 150…200K contribute to the observed improved clamping. These observations motivate a study of BALs based on extreme-triple-asymmetric epitaxial designs that achieve comparably high modal gains at 25°C to those seen at 150…200K. BALs fabricated with such designs operate with similar optical efficiency to best 200K results. Overall, if BALs using high modal gain designs can be realized with best-in-class series resistance, then exceeding conversion efficiency of 80% is plausible at room temperature.