and data-center networks 3, 6, 7

Integrating photonics with advanced electronics leverages transistor performance, process fidelity and package integration, to enable a new class of systems-on-a-chip for a variety of applications ranging from computing and communications to sensing and imaging. Monolithic silicon photonics is a promising solution to meet the energy efficiency, sensitivity, and cost requirements of these applications. In this review paper, we take a comprehensive view of the performance of the silicon-photonic technologies developed to date for photonic interconnect applications. We also present the latest performance and results of our "zero-change" silicon photonics platforms in 45 nm and 32 nm SOI CMOS. The results indicate that the 45 nm and 32 nm processes provide a "sweet-spot" for adding photonic capability and enhancing integrated system applications beyond the Moore-scaling, while being able to offload major communication tasks from more deeply-scaled compute and memory chips without complicated 3D integration approaches.

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A full optical chip-to-chip link is demonstrated for the first time in a wafer-scale heterogeneous platform, where the photonics and CMOS chips are 3D integrated using wafer bonding and low-parasitic capacitance thru-oxide vias (TOVs). This development platform yields 1000s of functional photonic components as well as 16M transistors per chip module. The transmitter operates at 6Gb/s with an energy cost of 100fJ/bit and the receiver at 7Gb/s with a sensitivity of 26µA (-14.5dBm) and 340fJ/bit energy consumption. A full 5Gb/s chip-to-chip link, with the on-chip calibration and self-test, is demonstrated over a 100m single mode optical fiber with 560fJ/bit of electrical and 4.2pJ/bit of optical energy.

A record low energy (250fJ/bit) intra-chip electronic-photonic link is demonstrated at 5Gb/s on a 3D-integrated wafer using through-oxide-vias (1.45fF-per-via) for the first time. The receiver sensitivity was -19.3dBm and the on-chip laser energy was 6fJ/bit.