Low-diffraction beaming in plasmonic crystals.

We analyze the propagation of electromagnetic modes guided by periodic plasmonic structures. We use full-wave solutions of Maxwell equations to calculate dispersion of these modes and derive analytical description of their optical properties. Finally, we demonstrate that, at a certain frequency range that can be controlled by the geometry, diffraction of these guided states is strongly suppressed, leading to formation of low-diffraction beams. A beaming phenomenon, consistent with earlier experiments, can be used as the foundation for on-chip communication or microscopy.