Beam splitting with a modified metallic nano-optic lens

Abstract

In this letter, the authors show with finite-difference time-domain simulations the beam splitting of a metallic nano-optic lens structure modified by loading a metal block adjacent to the nanoslits. A model that considers the nearby space between the metal block and metallic lens as an equivalent surface-plasmon-waves-coupled subwavelength cavity is proposed. In the model, bound surface plasmon mode evolves into unbound free space mode with widening of the cavity, and conditional diffraction of optical wave through the lateral openings (size ∼ wavelength) of the cavity leads to shaping of split beams in the intermediate zone.