Genetic optimization of double subwavelength metal slits surrounded by surface dielectric gratings for directional beaming manipulation

In this work, a model of double subwavelength metal slits surrounded by surface dielectric gratings is proposed for the directional beaming based on surface plasmon polariton (SPP). A genetic algorithm (GA) in conjunction with the finite-difference time-domain (FDTD) method is employed to optimize this structure, which leads to the high-efficiency directional beaming at any angle in a broad range (from 0° to 70°). The results show that the furthest propagation distance of the beaming can reach more than 25 μm, the maximum deflection efficiency can reach 97.37%, and the enhancement factor of the beaming can reach 7.58 × 102. The acceptable perturbation range of optimum structures is also obtained, which indicates the feasibility and realization of this model.