Gain-assisted trapping of light in tapered plasmonic waveguide.

We have investigated the slow light and trapping effects in tapered metal-insulator-metal plasmonic waveguides. It is found that a significant reduction of group velocity (<0.01c) can be obtained when considering the intrinsic loss of realistic metal. The theoretical analysis shows that the group velocity can be further decreased, even approach zero in the lossless metallic waveguides. The perfect trapping of light is realized when an appropriate gain material is incorporated in the core layer to compensate metallic loss. The proposed ultracompact configuration may find excellent applications on nanoscale optical storages.