Fig. 3: Three-layer SM-AONN.

a The photo of the connected three-layer networks. b The packaged single layer within one chip. c The false-color image of MZI mesh and AONUs. Black, Si waveguide. Green, electrodes of thermally-tunable MZI. d The detailed AONUs of a single layer. The structure of each AONU has been shown in Fig. 2d.