Wednesday, February 21, 2007

Smaller, Cheaper, Better Lasers

Continued from page 1

By Kate Greene

Chang-Hasnain realized that a novel mirror structure could yield benefits with only one layer. In the paper, her group reports a mirror that consists of thin pieces of aluminum gallium arsenide, separated by air, with an air gap between the laser's active region and the mirror.

The photons from the active region enter the aluminum gallium arsenide pieces; then, because of the optical interaction between the material and air, they take a 90º turn, reflect off the other pieces, come back, and make another 90º turn into the active region. "It's so simple, one must think it's been invented before," says Chang-Hasnain, "but it was not."

In this first prototype, her group was able to reduce the thickness of the typical laser cavity mirror from five micrometers to less than a quarter of a micrometer. The researchers also found that the mirror worked well for a variety of wavelengths of light, which increases its range of applications. And because photons don't have to travel through as many layers, fewer photons are lost. This means that laser efficiencies can be improved.

"It's an interesting and somewhat surprising solution in this field after so many years of research in the VCSEL research community," says Shun Lien Chuang, professor of electrical and computer engineering at the University of Illinois in Urbana.

The immediate applications, says Chang-Hasnain, would be in telecommunications. The lasers could be useful in bringing fiber optics to people's homes for ultrafast Internet connections. If the appropriate materials were used, however, the mirrors could also be incorporated into HD-DVD players. The researchers are currently filing a patent. Although she doesn't yet have a time line for commercialization, she believes the technology is "very close to realization."