  We motivate a new canonical strategy for integrating photonic neural networks
(NNs) by leveraging 3D printing. Our believe is that a NN's parallel and dense
connectivity is not scalable without 3D integration. 3D additive fabrication
complemented with photonic signal transduction can dramatically augment the
current capabilities of 2D CMOS and integrated photonics. Here we review some
of our recent advances made towards such a breakthrough architecture.
