Guest Editors’ Introduction: Silicon Nanophotonics for Future Multicore Architectures

h IT IS OUR pleasure to introduce this Special Issue on Silicon Nanophotonics for Future Multicore Architectures. The need for high-performance and energy-efficient communication between processing cores has never been more critical. The increase in core counts in emerging chip multiprocessors (CMPs) has put more pressure on the communication fabric to support many more streams of high bandwidth data transfers than ever before. An important consequence of this trend is that chip power and performance are now beginning to be dominated not by processor cores but by the components that facilitate transport of data between processors and to memory. Unfortunately, traditional electrical wires that make up the backbone of communication fabrics on CMPs today are facing unprecedented challenges in ultradeep nanoscale CMOS fabrication technologies. These wires are becoming slower, more power hungry, and less reliable. We are thus at a critical juncture where the power, bandwidth, and latency costs of communication must scale favorably to meet the needs of processing chips in the near future. A failure to adequately respond to this challenge will create a brick wall that will impede advances in all forms of computing. Fortunately, silicon nanophotonics has emerged in recent years as one of the most promising solutions to overcome the challenge of worsening communication performance with technology scaling. Recent breakthroughs in silicon nanophotonic device fabrication and CMOS integration have presented computer architects with an opportunity to explore both on-chip and chip-to-chip communications with optical networks that have significant advantages in bandwidth density, energy efficiency, and propagation delay over traditional electrical solutions. Not surprisingly, the challenge of designing silicon nanophotonic communication fabrics is today actively being pursued by a number of researchers worldwide, and from a variety of different perspectives. New nanophotonic devices (e.g., modulators, photodetectors, waveguides) are emerging from academia and research labs, as are new nanophotonics-based on-chip network architectures, and tools for rapid design and analysis. Many semiconductor companies have begun investing heavily into silicon nanophotonics and are releasing functional prototypes. Silicon photonic foundries are also emerging to allow low-cost fabrication of nanophotonic components on silicon chips. This special issue of IEEE Design & Test presents a collection of articles that highlight recent advances in the field of silicon nanophotonics, with a critical view in regards to advantages, limitations, and specific challenges. The articles selected include a tutorial on nanophotonic technology for multicore systems and investigations on photonic network design for GPUs, novel chip-to-chip interconnect