Slow-light enhanced nanoscale plasmonic waveguide sensors and switches

In this paper, we introduce slow-light enhanced nanoscale plasmonic waveguide devices for manipulating light at the nanoscale. In particular, we investigate nanoplasmonic metal-dielectric-metal (MDM) waveguide structures for highsensitivity sensors. Such plasmonic waveguide systems can be engineered to support slow-light modes. We find that, as the slowdown factor increases, the sensitivity of the effective index of the mode to variations of the refractive index of the material filling the structures increases. Such slow-light enhancements of the sensitivity to refractive index variations lead to enhanced performance of active plasmonic devices such as sensors. We consider Mach-Zehnder interferometer (MZI) sensors in which the sensing arm consists of a slow-light waveguide based on a plasmonic analogue of electromagnetically induced transparency (EIT). We show that a MZI sensor using such a waveguide leads to approximately an order of magnitude enhancement in the refractive index sensitivity, and therefore in the minimum detectable refractive index change, compared to a MZI sensor using a conventional MDM waveguide.