Non-polar GaN substrates and low-defect crystal growth will have an important part to play in powerful, practical green laser diodes.
Nine research groups have begun tackling the challenge of producing a high-power 500 nm semiconductor laser in a three-year US-based research program called VIGIL.
The teams met to initiate the program at the end of November, and they have until June 2009 to hit the first milestone and produce a workable green laser based on GaN.
VIGIL stands for Visible InGaN Injection Lasers, a name that reflects the need to include high proportions of indium to obtain green light from GaN-based laser diodes.
"There's a technical problem with getting green [light] out of nitride material," explained Henrik Temkyn, VIGIL's program manager at the US Defence Advanced Research Projects Agency (DARPA). "If you increase the amount of indium, the efficiency goes down."
Once room-temperature operational lasers have been demonstrated, official second and third phase goals include attaining 100 mW and 1 W continuous wave power output respectively. Temkyn, however, suggests that after initial lasing is shown he simply "would like power output at 700 mW from a single aperture". http://optics.org/cws/article/research/32395