Imagine a projection-style TV that fits in your hand, but which can fill a whole wall with a full-color, high-resolution picture that’s as bright as any you’ve seen. Or a light bulb an inch or two high that fills a room with pleasing white light, but without the heat and wasted energy of an incandescent bulb.

In terms of technology, two of the three things needed to make those happen are already available. Efficient and inexpensive red lasers have been around as long as CDs, and blue lasers are now entering the home en masse inside high-resolution Blu-ray video players. What’s missing is a low-cost green laser to complete the red-blue-green trifecta that is the basis for most video displays and cool, “natural” room light.

In November Darpa, the famed Pentagon technology-funding agency, unveiled a green-laser initiative that included grants for nine universities and research centers, mostly in the U.S. but also in Poland. Darpa’s usual pattern is to fund technologies that, while having potential long-term civilian applications, have a more immediate military
use. The military applications for green lasers, besides projection displays in aircraft and military vehicles, are believed to include submarine-to-ship communications, because green light travels easily underwater.The main research effort involves finding a way to use super-low-cost, computer-style semiconductors to create green lasers, the same
way red and blue lasers in consumer products are made. The semiconductors used in green lasers aren’t made from familiar silicon but from other metals, notably gallium nitride and indium nitride. Unfortunately, producing a green-laser semiconductor involves mixing more of the two metals in a single compound than the metals themselves care to have happen. “The indium just doesn’t want to stay there,” says Christian Wetzel, a physicist at the Rensselaer Polytechnic Institute.

Having a green laser costing a few dollars, and later a few pennies, would also help with the transition away from incandescent bulbs toward white-light-emitting diodes, which are increasingly being used to replace traditional bulbs. The cost of LEDs is falling, but green-laser technology could make their price plummet, said UC Santa Barbara physicist Steven DenBaars. One product green lasers won’t make possible are the higher-capacity storage products that followed blue lasers. The reason is basic optics. Compared with green ones, blue lasers have a shorter wavelength, meaning their light can be focused on a smaller area. As a result, more “blue-laser bits” can be fit onto a disk than would be possible with a green laser.

(Source: Wall Street Journal - February 2008)