Optical transistor in a photonic crystal circuit: using the control pulse (green), the gate is opened to let the signal pulse (red) pass through using non-linear effects to dynamically change material properties such as the refractive index.

The key role of a photonic layer is not only to provide point-to-point broad bandwidth optical link between different cores and/or the off-chip traffic, but also to route this traffic with an array of nanophotonic switches.