The field of Silicon Photonics has developed in order to provide optical interconnects that are faster and more efficient than their electrical counterparts. Much progress has been made but such optical inter- and intra- chip interconnects are still out of reach. Surprisingly, material incompatibility is the key issue. While silicon is a favourite of both photonics and electronics, photonics also requires a lower cladding for its waveguides. This takes the form of the thick oxide layer of a Silicon-on-Insulator (SOI) wafer. As such a layer would trap heat in the transistors, reducing the integration density, this is unacceptable to the electronics industry.
Our invention uses surface plasmon modes to guide light using a single interface between a metal and a dielectric. We exploit the phenomenon of extraordinary sensitivity to realise a low loss, low power consumption optical modulator based on the high speed (40GHz+) free carrier dispersion effect. Using surface plasmon modes to guide light in this way avoids the need for the problematic lower cladding layer and permits front-end integration with minimal changes to electrical device manufacturing processes currently in use.
The front-end integration of electronics and photonics will enable the next generation of computer systems providing cheap and effective on- and off- chip communications.
UK patent application 1313592.6.
International patent application PCT/GB2o14/051844, published 5 February 2015 as WO2015/015148