Design of mode conversion waveguides based on adiabatical mode evolution for mode division multiplexing

Mode conversion based on adiabatical mode evolution in a two-core configuration is proposed. The mode conversion feature is only dependent on the relationship between the effective mode indexes of the two cores in the configuration, which shows the highly flexible characteristics of the configuration and large fabrication tolerance. A mode wide bandwidth multiplexer/demultiplexer which is achieved by cascading the configuration is demonstrated numerically.