Design of directional beaming from a nanoslit in metallic film surrounded by metal-dielectric surface gratings

We propose a design scheme of a nanoslit in metallic film flanked by metal-dielectric surface gratings on the output side for directional beaming of transmitted optical field. Based on the effective excitation of surface plasmon polariton resonance mode in the metallic-dielectric-air/metal waveguide, directional beaming of light can be realized by tuning the surface grating depth. According to our theoretical design, a numerical simulation based on the finite-difference time-domain method was also undertaken, the results obtained match well with the theoretical prediction.