The Case for Hybrid Photonic Plasmonic Interconnects (HyPPIs): Low-Latency Energy-and-Area-Efficient On-Chip Interconnects

Abstract

Moore's law for traditional electric integrated circuits is facing increasingly more challenges in both physics and economics. Among those challenges is the fact that the bandwidth per compute on the chip is dropping, whereas the energy needed for data movement keeps rising. We benchmark various interconnect technologies, including electrical, photonic, and plasmonic options. We contrast them with hybrid photonic-plasmonic interconnect(s) [HyPPI(s)], where we consider plasmonics for active manipulation devices and photonics for passive propagation integrated circuit elements and further propose another novel hybrid link that utilizes an on-chip laser for intrinsic modulation, thus bypassing electrooptic modulation. Our analysis shows that such hybridization will overcome the shortcomings of both pure photonic and plasmonic links. Furthermore, it shows superiority in a variety of performance parameters such as point-to-point latency, energy efficiency, throughput, energy delay product, crosstalk coupling length, and bit flow density, which is a new metric that we defined to reveal the tradeoff between the footprint and performance. Our proposed HyPPIs show significantly superior performance compared with other links.

Fundamental Scaling Laws in Nanophotonics

“…Furthermore, we show that the high jitter-length sensitivity of plasmonic links radically improves upon hybridization (purple data Fig. 5)36. Comparing the performance of optical to electronic link performance has relevance for photonic technology road-mapping; the inherent capacitive link performance limitations arising from charging electrical wires (green data, Fig.…”

“…However, together with its 10 4 times smaller cavity footprint, such MNP lasers may bypass external electro-optic modulators, since the power overhead for cavity tuning and modulation can be saved, thus reducing optical link complexity and increasing link performance35. In addition, a more detailed external and internal modulation strategies analysis could be found in our previous work where we analyzed the link performance of all electronic, photonic, plasmonic and hybridization interconnects in the latency, energy, throughput and other comprehensive FOMs36.…”

“…Based on the analysis of individual devices, we investigate scaling-based performance variations of various interconnect (IC) technology options36. We deploy the aforementioned FOM comprised of the link data speed divided by its ‘cost’ given by energy consumption times link footprint (Fig.…”

“…Further, we consider a photonic-plasmonic hybrid link, where all active devices are based on MNP cavities, but the passive interconnections are regular low-loss SOI waveguides (Fig. 5)36. As a comparison we relate these four photonic link FOMs to an electrical IC, which is based on the 22 nm technology node53.…”

Active material, optical mode and cavity impact on nanoscale electro-optic modulation performance

“…In general, the modulator performance depends greatly on the underlying waveguide determining coupling and propagation losses, the confinement factor of the active material with the optical mode, the strength of the optical index change being altered [10,35] and subsequent impacts on energy efficiency, modulation speed, footprint and optical power penalty [12,[36][37][38][39]. While previous works focused on addressing these in an ad hoc manner [10,15,16], here we show the first systematic approach for a selected set of active materials (silicon, ITO, and graphene), optical waveguide modes (bulk, slot, and hybrid-plasmon) and a cavity [Fabry-Pérot (FP)].…”