Progress of blue and green InGaN laser diodes

Abstract
Mobile laser projection is of great commercial interest. Today, a key parameter in embedded mobile applications is the optical output power and wall plug efficiency. We report improvements of the performance of true blue single mode InGaN laser at 450nm with output power of more than 200mW in cw operation for temperatures between 20°C and 60°C. We succeeded in temperature independent high wall plug efficiency of 15-18% for stable output power levels from 100 to 200mW with estimated life times >4000h in cw operation. Furthermore, we present pioneering studies on long green InGaN laser diodes. The technological challenge is to achieve InGaN-quantum wells with sufficiently high material quality for lasing. We investigate the density of non radiative defects by electro-optical measurements confirming that low defect densities are essential for stimulated emission. Laser operation at 516nm with more than 50mW output power in cw operation is demonstrated in combination with a high wall plug efficiency of 2.7%.