A long-standing goal of the photonics and semiconductor industries is the dense integration of optical components into electronic microprocessor chips to overcome bandwidth and power density limitations of electrical connections. However, fabrication incompatibilities mean that chip-scale integration of photonics and electronics has so far remained limited. Now, Chen Sun, Mark Wade, Yunsup Lee, Jason Orcutt and colleagues in the USA have demonstrated integration of 70 million transistors and 850 photonic components in a chip that exploits the electronics for logic operations and optics for rapid communication with the memory. The system houses a RISC-V microprocessor and a separate 1 MB random access memory and was shown to be capable of three-dimensional graphics rendering. Communication between the microprocessor and the memory by optical means was demonstrated over arbitrary distances (for example, up to 20 m by fibre). A 1,183-nm wavelength solid-state laser provides a light source for integrated modulators made from 10-mm-diameter ring-resonators. The full-duplex communication between memory and microprocessor runs at 2.5 Gb s−1 in each direction, for an aggregate of 5 Gb s−1. The team notes that 55 Gb s−1 should be possible without additional fibres, by using multiple wavelengths simultaneously. As processor load can affect the chip temperature (by up to 8 K in the present case), and thus affect operation of the optical transmitters and receivers the team implemented a thermal-tuning feedback circuit to control ring modulator microheaters, alleviating the temperature variation issue.
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Pile, D. Electronic–photonic chip. Nature Photon 10, 145 (2016). https://doi.org/10.1038/nphoton.2016.31
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DOI: https://doi.org/10.1038/nphoton.2016.31
