Surface emitting laser demonstrated to deliver error-free data at 40 Gbit/s
Today’s commercial lasers can send up to 10Gb of data per second through optical fibers. This applies to both conventional lasers and to surface emitting lasers. Researchers at Chalmers University of Technology have managed to increase the speed of the surface emitting laser four times, and see potential for further capacity increase.
“The market for this technology is gigantic. In the huge data centers that handle the Internet there are today over one hundred million surface emitting lasers. That figure is expected to increase a hundredfold,” says Professor Anders Larsson, who has developed the high-speed laser together with his research group in optoelectronics.
Unlike a conventional laser the light from a surface-emitting laser is emitted from the surface of the laser chip (not from the edge), like in an LED. The gain is the ability to not only fabricate, but also 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. It requires less power without losing speed. The energy and power consumption is a tenth of what a conventional laser requires at 40 Gbit/s 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 eg circuits in a computer (including drive electronics and receiver) will be no more than 100 fJ/bit.
The next step for the Chalmers researchers is to modify the design and refine the ways to control the laser, to increase speed and reduce power consumption even further.
“Each wafer contains Up to 100 000 lasers chips. The surface emitting lasers can both be fabricated and tested before we cut the wafer into chips,” says Anders Larsson, Professor in Optoelectronics at Chalmers University of Technology.
“We strive to meet market demands ten years from now,” says Anders Larsson, who estimates that we by 2020 will need energy-efficient cables that can handle 100 Gbit/s per channel. The research is performed at the Chalmers research center FORCE.
It is funded by Swedish Foundation for Strategic Research, SSF, and by the EU through the project VISIT. Participating companies in the European project are IQE Europe (UK), VI Systems (Germany) and Intel (Ireland). Informal partners in the project are Tyco Electronics and Ericsson (both Sweden). The findings are published in Electronics Letters from IEEE Explore.
Visit the EU-projektet at www.visit.tu-berlin.de
Visit the FORCE, Fibre Optic Communications Research Centre at www.chalmers.se/mc2/force-en