Intel scientists boost silicon optics
Previous attempts to modulate light with silicon have had modulation frequencies of the order 20MHz. To obtain higher frequencies III-V or electro-optic materials such as lithium niobate are used.
The scientists maintain that the new Intel silicon waveguide structure is compatible with complementary MOS (CMOS) processing. Indeed, their devices were produced on a CMOS line at Intel.
The device uses the "free carrier plasma dispersion effect". The MOS capacitor modulates the charge density in silicon that in turn modifies the material’s refractive index. This introduces a phase shift in the light.
These phase shifters are used in Mach-Zehnder interferometers (MZIs) to achieve the modulation. In the MZIs, the light beam is split, put through the phase shifters and finally recombined to interfere.
