Giant power enhancement for quasi-omnidirectional light radiation via ε-near-zero materials.

We theoretically demonstrate a giant power enhancement effect for a line current source in a ε-near-zero (ENZ) two-dimensional (2D) shell with proper physical dimensions. Compared with the traditional high-ε dielectric approach, the ENZ scheme has the prominent advantage that the radiation performance is less sensitive to the outer radius of the shell, which is critically important for real applications where micro-nano fabrications are often involved. The enhancing performance is independent on the position of the source inside the ENZ shell and could be substantially strengthened by incorporating more sources, while the quasi-omnidirectional radiation pattern could be managed to have negligible variance, as evidenced by a particular example with an inner radius of the shell equal to 0.156λ. Compared with the single source case, two identical sources with a phase difference less than 134° will raise the total radiation power more than 4 folds and the maxima will be about 30 when they are in phase. The field analysis shows that this quasi-isotropic radiation enhancement is mainly contributed by the amplification of the isotropic zeroth order mode radiation while the higher orders with anisotropic emission patterns are effectively suppressed by the specifically designed ENZ shell. In the end, a practicable device employing 4H-silicon carbide (4H-SiC) naturally available with ENZ properties in the mid-infrared regime is numerically proposed, which could provide more than 10 times of radiation enhancement through optimizing the permittivity of the inner dielectric cylinder. These results may find very important applications in the design of novel devices for mid-infrared photon sources or detectors.