Maximizing waveguide integration density with multi-plane photonics

We propose and experimentally demonstrate a photonic routing architecture that can efficiently utilize the space of multi-plane (3D) photonic integration. A wafer with three planes of amorphous silicon waveguides was fabricated and characterized, demonstrating $<3\times10^{-4}$ dB loss per out-of-plane waveguide crossing, $0.05 \pm 0.02 $ dB per interplane coupler, and microring resonators on three planes with a quality factors up to $8.2 \times 10^{4}$. We also explore a phase velocity mapping strategy to mitigate the crosstalk between co-propagating waveguides on different planes. These results expand the utility of 3D photonic integration for applications such as optical interconnects, neuromorphic computing and optical phased arrays.