Fast Laser Could Speed Communications

The speed of surface-emitting lasers has been increased four times to an error-free data rate and record of 40 Gb – a breakthrough that could lead to faster Internet traffic, computers and mobile phones.

Up to 100,000 lasers can be fabricated and tested before we cut the wafer into chips, Anders Larsson says. (Image: J-O Yxell)

“The market for this technology is gigantic. In the huge data centers that handle the Internet, there are today over 100 million surface-emitting lasers. That figure is expected to increase a hundredfold,” said Anders Larsson, professor at Chalmers University of Technology and, together with his research group in optoelectronics, developer of the high-speed laser.

Unlike with a conventional laser, the light from a surface-emitting laser is emitted from the surface of the laser chip, not the edge. The gain is the ability not only to fabricate but also to test the lasers on the wafer (a 75-mm-wide substrate of semiconductor material of industrial type) before it is cut into individual chips for assembly. The lasers work directly where they sit on the wafer. Conventional lasers work only after partition. The ability to test up to 100,000 lasers on a wafer reduces the cost of production to one-tenth compared with conventional lasers.

The laser volume is smaller and requires less power at the same speed. The power consumption is one-tenth of what a conventional laser requires at 40 Gb – only a few hundred fJ/bit. If Anders Larsson and co-workers succeed in their development, he expects that the power consumption of a complete optical link between circuits in a computer (including drive electronics and receiver) will be no more than 100 fJ/bit.

“The laser's unique design makes it cheap to produce, while it transmits data at high rates with low power consumption,” Larsson said.

The combination is unique and opens up to a large-scale transition from electrical cables to optical cables in computers and to side equipment as a substitute for USB cables, for instance.

“Here we are heading for a power catastrophe. The data centers represent a few percents of America's entire electricity consumption,” he said.

The next step for the Chalmers researchers is to modify the design and refine the ways to control the laser, to increase speed, and to reduce power consumption even further.

For more information, visit: www.chalmers.se/en