26 February 2010


Osram details record output & efficiency cw direct green InGaN laser diodes

In an invited talk at the recent SPIE Photonics West 2010 event in San Francisco last month, the team of Dr Stephan Lutgen from Osram Opto Semiconductors GmbH in Regensburg, Germany presented R&D data demonstrating the first direct-emitting ‘true green’ indium gallium nitride (InGaN) ridge-wavegide (RWG) laser diode emitting at a wavelength of 515nm in continuous-wave (cw) mode with record output power up to 50mW. The work has since been published online and will appear as ‘Progress of blue and green InGaN laser diodes’ by S. Lutgen et al in Proc. SPIE, Vol. 7616, 76160G (2010).

Osram Opto says that this level of optical power is necessary for RGB scanning beam laser projection, with 10–15 lumens on the screen. The green laser diode is grown on a commercially available c-plane GaN substrate. Also, the laser demonstrated a wall-plug efficiency of 2.7%, which the firm describes as a key milestone towards the success of direct green InGaN-based laser diodes for laser displays.

To achieve true green laser emission in continuous-wave operation, several key obstacles needed to be resolved, says Osram Opto. Perhaps the most important 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 of 515nm and above. Minimization of Ga/In alloy fluctuations and point defects during epitaxial growth was essential 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,” believes Dr Volker Haerle, vice president of R&D at OSRAM Opto Semiconductors.

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

See related items:

Kaai demos 523nm continuous-wave green laser diode

Sumitomo boosts 520nm green InGaN laser to continuous-wave operation

Osram develops 50mW direct-emitting green InGaN laser

Sumitomo Electric claims first pure-green semiconductor laser

Nichia pushes InGaN lasers nearer to green via 515nm emission

Osram Opto claims first 500nm InGaN laser

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