4. Optical interconnections: nanophotonics for electronics

The extensive miniaturization of transistors has enabled a spectacular increase in the integration density of electronic circuits, which now number several hundred million transistors per cm ² . On the other hand, the densification of metal interconnections in these circuits poses major problems, as it affects the propagation of electrical signals by slowing them down, distorting them and "de-synchronizing" them. There are typically more than ten levels of interconnection. The first levels correspond to local links between transistors, the intermediate levels ensure medium-distance links within the electronic circuit's "functional blocks", and finally the last levels are those of global links which enable the propagation of "global" signals on the chip, in particular the clock signal (fig. a). The propagation of the clock signal...