Two-Beam Emitting Via a Single Subwavelength Metal Slit Surrounded by Mixed-Period Dielectric Grooves

We use mixed-period dielectric grooves to surround a single metal slit to realize two-beam nonsymmetrical and symmetrical emitting for the transmitted light emerged from the subwavelength slit. This proposed slit-groove-based structure is formed by combining two typical slit-groove structures, both possessing unidirectional beaming but with different beaming angles. Here, the typical slit-groove structure refers to the single slit perforated in the metal film, and the slit is surrounded by periodic dielectric grooves on the exit surface of the metal film. By using the finite-difference time-domain method, the simulation results show that two-beam emitting can be produced with flexible splitting angles via such combined structure. In addition, the power ratio of two-beam emitting can be changed via using appropriate groove number to surround the slit of the combined structure.