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This exploratory project pushes the limits of current photonic technology.
SOI 200mm wafer processed on a standard CMOS fabrication line with numerous nanophotonic circuits
Photonic crystal composed of a periodic array of holes etched in silicon slab. False-colored SEM image.
Periodic array of holes etched in silicon slab that comprises silicon photonic crystal
Silicon photonic crystal waveguide connected to photonic wire waveguide. False-colored SEM image.
Dark blue bar is a silicon photonic wire waveguide. A packet of light pulses, shown as a train of white balls, is propagating along the silicon waveguide with a speed not much different from a speed of light in vacuum.
Photonic wire waveguide is butt-coupled to the silicon photonic crystal waveguide defined by a periodic array of holes etched in a silicon membrane. 
To control the speed of light electrically two lateral electrical contacts are deposited on top of a silicon membrane. This forms an integrated microheater. The trick is to position the contacts as close as possible to the waveguide core and, at the same time, to avoid excessive parasitic losses due to absorption in metal. 
When the voltage is applied to the contacts the current is passing across the photonic crystal waveguide. This current heats the silicon membrane that in turn results in slight changes in the refractive index of silicon due to thermo-optic effect.