Enhanced near-field optical moir\'{e} effect.

We demonstrated an enhanced near-field optical Moir\'{e} effect by inserting a silver slab between two subwavelength gratings. The evanescent fields can be greatly enhanced by the surface plasmon excitation supported by the silver slab, which leads to a remarkable contrast improvement in the Moir\'{e} fringes. The crucial role of surface plasmon excitation was elucidated by numerical simulation. Experimental enhanced near-field optical Moir\'{e} effect, which agreed very well with the simulation, was also presented. This new effect can be used to extend the conventional Moir\'{e} techniques into usage of subwavelength gratings.