  We predict an optical curtain effect, i.e., formation of a spatially
invariant light field as light emerges from a set of periodic metallic
nano-objects. The underlying physical mechanism of generation of this unique
optical curtain can be explained in both the spatial domain and the wave-vector
domain. In particular, in each period we use one metallic nanostrip to equate
the amplitudes of lights impinging on the openings of two metallic nanoslits
and also shift their phases by pi difference. We elaborate the influence on the
output effect from some geometrical parameters like the periodicity, the slit
height and so on. By controlling the light illuminated on metallic
subwavelength apertures, it is practical to generate optical curtains of
arbitrary forms, which may open new routes of plasmonic nano-lithography.

Optics