Surface emitting laser delivers error-free data at 40 Gbit/s

Researchers at Chalmers University of Technology have managed to boost the data rate of the surface emitting lasers by a factor of four, and they see potential for further increases.

Current commercial lasers (both conventional and surface emitting types) can transmit data over optical fibres at up to 10 Gbit/s.

As the name suggests, surface-emitting lasers emit light from the surface of the laser chip instead of from the edge as with conventional laser chips. This allows the laser chips to be tested on the wafer before it is cut into individual dice. By contrast, conventional lasers work only after they been cut from the wafer. The ability to test up to 100,000 lasers on a wafer reduces the production cost by a factor of 10 compared to conventional lasers.

In addition, the laser chips are smaller and require less power for the same speed. For example, the energy consumption of a surface-emitting laser at 40 Gbit/s is a tenth of what a conventional laser requires, or just a few hundred femtojoules per bit. If the researchers see their expectations realised, they predict that the energy consumption of a complete optical link (including the driver and receiver electronics), for example between modules in a computer, will be no more than 100 fJ/bit.

The next step for the Chalmers researchers is to modify the design and refine the means for controlling the laser in order to raise the speed and reduce the power consumption even further.

The research was carried out at the Chalmers FORCE research centre and was funded by the Swedish Foundation for Strategic Research (SSF) and the EU through the VISIT project. The VISIT project participants are IQE Europe (UK), VI Systems (Germany) and Intel (Ireland), accompanied by informal project partners Tyco Electronics and Ericsson (both Sweden).

Image: Chalmers University of Technology