Invited Paper
Plasmonic Devices in Optical Interconnect Technology

Surface Plasmons Polaritons (SPP) are transverse magnetic (TM) polarized electromagnetic waves propagating under specific conditions along a metal-dielectric interface. Plasmon devices enable to carry optical signals and electric currents through the same thin metal circuitry, thereby opening the perspective of inserting electrically driven devices on the same circuitry on which light is propagating. Exploring the potential of an hybrid technology merging plasmon and silicon photonics on a single board, this contribution describes the efforts of the European FP7 projects PLATON & PHOXTROT towards the practical implementation and testing in true optical data processing conditions of plasmonic devices in optical interconnects implemented at various levels : optochip, optoboard and chip-to-board interfaces.

FP7 project PLATON showed that the plasmonic switches readily achieve a better figure of merit than alternative technologies pertinent in this context. FP7 project PHOXTROT is currently considering the use of plasmonic devices to manage several critical issues of chip-to-board optical links. Both projects show that there is much room for significant improvements if the issue low-loss and CMOS compatible plasmonic devices is consistently addressed in the three plasmonic waveguide configurations allowing most short-term application perspectives in optical interconnect technology: LRSPP, slot or DLSPP waveguides. For each family, coupling interface solution featuring acceptable losses can be designed.

FP7 PLATON showed that low-loss figures can be achieved by an hybrid SOI/plasmonic design reducing plasmonic function to short active lengths of optical circuits. CMOS compatibility basically means to avoid the use of gold or silver which are routineley used in basic plasmonic research. This issue will be discussed on the basis of three scenarios: polycrystalline aluminum, crystalline aluminum and Titanium Nitride (TiN). The latter is also offering like thermal stability, can be grown epitaxial on many substrates including silicon, does not oxidize like silver or copper and was shown to provide higher mode confinement in comparison to gold. We will conclude by sketching the impact of these CMOS compactible materials on plamonic devices relevant in the optical interconnect context such as high speed MZI modulators, switches and power monitors.

alain.dereux@u-bourgogne.fr