Tokyo, Japan, September 10, 2004--Fujitsu Limited and a research group at the University of Tokyo led by Professor Yasuhiko Arakawa, today announced the joint development of a quantum dot laser that succeeds in minimizing temperature-sensitive output fluctuations, which was not possible with semiconductor lasers in the past. The newly developed quantum dot laser achieves high-speed operation of 10 gigabits per second (Gbps) across a temperature range of 20°C to 70°C.
The new semiconductor laser features extremely minimal temperature fluctuations, and uses 3-dimensional nano-structured quantum dots in the light-emitting area. Professor Yasuhiko Arakawa of the University of Tokyo theorized in 1982 that the operation of quantum dot lasers does not rely on temperature, but such temperature-independent operation had only been realized at low temperatures thus far.
By increasing optical gain through multi-layering quantum dots into 10 layers, raising the density of each layer, p-doping (inserting a p-type impurity in close proximity to the quantum dots), and by using a laser structure that features low parasitic capacitance for optimized high-speed modulation, the new technology successfully achieves high-speed operation of lasers with temperature-independent output at temperatures exceeding room temperature.
The newly developed quantum dot laser realized high-speed operation of 10Gbps at wavelengths of 1.3 micrometers which are used for optical transmission systems, for a temperature range from 20°C to 70°C without drive current adjustments. The achieved 10Gpbs high-speed operation is the world's fastest for a quantum dot laser for use in optical telecommunication systems.
Average optical output variances measured for 10 Gbps modulation operation across various temperatures depicted that for strained quantum-well lasers, the average optical output dropped significantly at higher temperatures, while the average light output variance for the new quantum dot laser was less than 5%.
This breakthrough technology will pave the way for compact, low-cost, and low power-consumption optical transmitters targeting optical metro-access systems and high-speed optical LANs.