Incandescent bulbs have given way to CFL and LEDs, but these lighting technologies may be destined for extinction as well. A team of scientists at Arizona State University have developed a laser that can produce pure white light that is brighter and more efficient than even the best LEDs. Technically, thelaser itself isn’t white from the start, but the clever use of nanomaterials allows three colored beams to become one white beam.
Lasers have always had appeal for lighting technology as they’re very bright, work over long distances, and have high efficiency. The problem has always been that lasers can’t be white. This work builds on a laser created in 2011 at Sandia National Laboratories. However, that was merely a proof of concept, not a functional device. The ASU team’s white laser produces enough light that it’s visible to the human eye. That’s a step in the right direction.
There’s still no way to actually generate a white laser, but this breakthrough gets us to the same place by combining three beams. As you might expect, these are blue, red, and green, just like the subpixels on an LCD or AMOLED display. To make this happen, the team had to design a semiconductor laser capable of operating across the entire color spectrum, which turns out to be far from simple. They eventually found success with a nanoscale semiconductor based on an alloy of ZnCdSSe.
It was a significant undertaking to tune the semiconductors to produce the correct colors in proportional amounts. This was handled by carefully controlling the so-called “lattice constant,” the distance between the atoms in the semiconductor. The blue part of the spectrum was particularly troublesome, requiring the use of techniques to create the lattice first, then allow it to form the desired alloy.
The result of all this is white laser light, but the tunable nature of the semiconductor means thatthe laser can produce any color in the spectrum by increasing or decreasing the intensity of the red, green, and blue channels. It has a 70 wider color range and is more accurate than LEDs. While lighting is probably the most straightforward application, that’s only the beginning. The team believes the white light laser could be useful in display technology.
Before any of that can happen, the design needs to be refined. Right now it uses a conventional laser as a power source, but the semiconductor needs to be able to draw electrons from a battery to be practical. When that’s done, we could be well on our way to laser lighting and displays.