Nanoscale laser promises faster communications

Posted by Emma Woollacott

Tempe, Arizona – The creation of the world's thinnest semiconductor laser has opened up the possibility of significant improvements in computing performance.

Smaller lasers can be more effectively integrated with small electronics components, with applications in computing and medical imaging.

The size of lasers in any one dimension has been thought to be limited to one-half of the wavelength involved. Current theory says you can't make a laser smaller than this diffraction limit – smaller than 250 nanometers for a semiconductor laser for communications devices.

But researchers at Arizona State University and the Technical University of Eindhoven in the Netherlands are showing there are ways around this supposed limit. One is to use a combination of semiconductors and metals such as gold and silver.

"It turns out that the electrons excited in metals can help you confine a light in a laser to sizes smaller than that required by the diffraction limit," ASU team leader Cun-Zheng Ning explains. "Eventually, we were able to make a laser as thin as about one quarter of the wavelength or smaller."

Ning and colleagues have achieved this by using a "metal-semiconductor-metal sandwich structure," in which the semiconductor is as thin as 80 nanometers and is sandwiched between 20-nanometer dielectric layers before putting metal layers on each side.

They have demonstrated that such a semiconductor/dielectric layer can actually emit laser light – a laser with the smallest thickness of any ever produced. So far, though, it's worked only at low temperature, and the next step is to achieve the same laser light emission at room temperature.

"This is the first time that anyone has shown that this limit to the size of nanolasers can be broken," Ning says. "Beating this limit is significant. It opens up diverse possibilities for improving integrated communications devices, single molecule detection and medical imaging."

Nanoscale lasers can also be integrated with other biomedical diagnostic tools, making them work faster and more efficiently, he says.

"Nanolasers can be used for many applications, but the most exciting possibilities are for communications on a central processing unit (CPU) of a computer chip," Ning says.

The teams' findings are reported in Optics Express.