Ahead of the worldwide strong research activities on direct green InGaN-based laser diodes OSRAM opto semiconductors researchers could achieve recently ground breaking results. As presented on the Photonics West 2010 in San Francisco, the team of Dr. Stephan Lutgen demonstrated for the first time R&D-data up to 50mW continuous wave output power at 515nm from InGaN-based RWG-Laser.

This optical power level is necessary for rgb scanning beam laser projection with 10-15 lumen on the screen.The green laser emission of a laser diode grown on commercially available c-plane GaN substrate is shown in the picture. Further more, with the demonstration of 2.7% wall plug efficiency an important milestone towards the success of direct green InGaN based laser diodes in laser displays was done. Several key obstacles needed to be resolved until true green laser emission could be accomplished in continuous wave operation.

Probably the most important issue to resolve was the low crystal quality of the light emitting active layers (InXGa1-XN quantum wells) caused by the high indium content required to reach green emission wavelengths ≥515nm. Minimisation of Ga/In alloy fluctuations and point defects during the epitaxial growth was essentially to achieve higher cw output power levels.

“These compact, direct green laser diodes will reach efficiencies and output power to revolutionize the current markets for green lasers”, says Dr. Volker Haerle, Vice President R&D at OSRAM Opto Semiconductors.

Part of this work is sponsored by the German Ministry for Education and Research (FKZ 13N9373) as a research project for ultra-compact and mobile laser projection systems.