Extended Data Figure 1: Chip cross-section.
From: Single-chip microprocessor that communicates directly using light
a, Full chip cross-section (not to scale) from the silicon substrate to the C4 solder balls, showing the structures of electrical transistors, waveguides, and contacted optical devices. G, S, and D mark the structures that form the gate, source, and drain, respectively, of an electrical transistor. The minimum separation between transistors and waveguides is <1 μm, which is set only by the distance at which evanescent light from the waveguide begins to interact with the structures of the transistor. b, Transmission electron microscopy cross-section micrograph of an optical waveguide, before substrate removal.
