As copper interconnects reach their limit for transferring data, are popping up from industry leaders. Photonics seem to be the direction everyone is headed towards. Since fiber-optics have completely taken over for data backbones, optics will eventually reach the smallest interconnect. UCL and the London Centre for Nanaotechnology have created a contender, a quantum dot laser grow in a silicon substrate transmitting 10 Gbits/s at a 1.3 μm wavelength, geared towards being the first photonics link in telecommunications. A quantum dot is a bit of semiconductor matter with electrical characteristics that are closely related to the size/shape of the crystals they are grown in. The smaller the crystal, the larger the band gap of energy, or the difference between the highest electron valence band and the lowest conduction band. Quantum dot lasers use the dots as the active medium in the light emitting portion.
Normally there is a dislocation in the crystal structure caused by contrast in the silicon and the compound semiconductor. However, the UCL overcame this issue by making layers that prevent dislocations. And they have successfully demonstrated the 1.3 μm laser by direct epitaxial growth on silicon, with an optical output of 15 mW per facet at 20-70°C. The size of the lasers make them ideal for use within chip, not external like Light Peak and other such options. Professor Alwyn Seeds, principal investigator in the London Center for Nanotechnology spoke of the groups next step, "The techniques that we have developed permit us to realize the Holy Grail of silicon photonics - an efficient, electrically pumped, semiconductor laser integrated on a silicon substrate. Our future work will be aimed at combining these lasers with waveguides and drive electronics leading to a comprehensive technology for the integration of photonics with silicon electronics."
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