Asymmetric Positive-Negative Index Nonlinear Waveguide Couplers

Nonlinear optical couplers have attracted significant attention largely due to the many advantages they offer for optical communications and signal processing. Combined with the unique properties of an emerging new class of materials, metamaterials, nonlinear directional couplers open fundamentally new opportunities for the development of ultracompact signal processing functionalities for on-chip applications. In this paper, we explore theoretically nonlinear transmission properties of asymmetric nonlinear couplers with one channel made of positive index material and the other channel made of negative index material while only one of the channels is nonlinear. We demonstrate that such asymmetric couplers can be bi- and multistable, and we optimize the design with respect to the bistability threshold.