Side scattering shadow and energy concentration effects of epsilon-near-zero media.

By analytically and numerically investigating the near-field scattering properties of particles composed of epsilon-near-zero (ENZ) media, we reveal a unique scattering phenomenon which is hereby denoted as the side scattering shadow and energy concentration effect. The scattering of ENZ particles leads to the emergence of near-field "shadows," where the electric fields are significantly decreased to zero on two sides of the particle perpendicular to the incident direction. At the same time, the electric fields inside the particle are enhanced to a certain extent, indicating concentration of wave energy. These extraordinary behaviors can be well explained through the Mie scattering theory. Moreover, such unique effects robustly exist for isotropic and anisotropic ENZ particles of almost arbitrary shapes and with loss. We further demonstrate interesting applications of this effect, including the "quenching" of surface plasmons and the concentration of electromagnetic energy in the deep subwavelength scale. Our findings may inspire novel applications in nanophotonics.