COM•DTU, Denmark
Some members of the group who worked on the project have launched a start-up company called SEMuS Ltd. (Silicon External Modulator using Strain) and are seeking further investment to develop the technique into commercial computing applications.
In traditional silicon computer chips, copper wires are used to conduct electric current. Because the speed of transmission is limited by the maximum speed of electronic conduction, the capacity of these traditional chips is approaching a ceiling. The transmission of a signal via light pulses, photonics, is much faster than electronic transmission.
There is consequently a great deal of commercial interest in the development of optical modulators, devices that can transfer an electrical signal into an optical signal by controlling the transmission of an optical beam. Using these modulators, an optical signal could be transmitted on a chip, or between different chips, like an electric current through a wire.
Today, fast optical modulators can only be made from materials with so-called linear electro-optic properties. These materials are expensive to produce and not compatible with silicon chips. On-chip modulators made can be made in silicon, but are unsuitable for normal computers as they use a different method of transmission and have an extremely high power consumption.
The DTU team has developed a method to induce this crucial linear electro-optic effect in silicon, by breaking down its crystal lattice structure. This has the potential to lead to cost-effective and efficient on-chip silicon optical modulators.
The effect is induced by growing a special layer of glass on top of the silicon crystal, which expands and acts as a ‘straining layer’, putting stress on the silicon and deforming its crystal structure. The work is still being pursued at COM•DTU at the laboratory stage but SEMuS is investigating how the same technique could be used on a commercial scale.
“The impact of this work is that we can now see the possibility of the integration of electronics and photonics on one computer chip,” said Jacob Fage-Pedersen of COM•DTU. “With optical modulators as part of normal computer chips, we can also improve the speed of Internet connections with optical signals.”
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