Compact and wideband multiport plasmonic coupler–splitter based on coding metamaterials

Abstract

We propose plasmonic coupler–splitters based on embedded coding metamaterials. The fundamental transverse electric mode in a silicon waveguide is coupled to the surface plasmon polariton mode in plasmonic waveguides with high efficiency of nearly 95% and wide bandwidth of 1.45–1.65 µm, and then light is split into different output ports. To improve the performance of the devices, a multi-objective optimization scheme based on the non-dominated sorting genetic algorithm-II assisted by the direct-binary search method is applied in the design of coding metamaterials. The simulated results exhibit that utilizing our inverse design scheme, the plasmonic coupler–splitter can perform effective plasmonic coupling (total coupling efficiencies of more than 92%) and high-quality power splitting with various split ratios (split ratio errors lower than 1%) and output directions at a broad bandwidth (1.45–1.65 µm) simultaneously. The function of the frequency split can also be implemented in the same universal basic scheme. In comparison to previous works, we not only propose flexible coupler–splitter designs for various functions based on a universal design scheme, but also introduce effective algorithms for the inverse design of optical devices based on coding metamaterials.