Mode converter in metal-insulator-metal plasmonic waveguide designed by transformation optics

A metal-insulator-metal (MIM) waveguide can support two plasmonic modes. Efficient conversion between the two modes can be achieved by reshaping of both phase and power density distributions of the guided mode. The converters are designed with the assistance of transformation optics. We propose two practical configurations for mode conversion, which only consist of homogeneous materials yielded from linear coordinate transformations. The functionalities of the converters are demonstrated by full wave simulations. Without consideration of transmission loss, conversion efficiency of as high as 95% can be realized.