Far-Field Subwavelength Straight-Line Projection/Imaging by Means of a Novel Double-Near-Zero Index-Based Two-Layer Metamaterial

In this paper, for the first time, tuned near-zero-index materials are used in a structure for the long-distance projection of very closely spaced objects with subwavelength separation. Near-zero-index materials have never been used for subwavelength projection/imaging. The proposed novel structure is composed of a two-layer slab that can project two slits with a subwavelength separation distance to a long distance without diverged/converged interference of the two imaged waves. The two-layer slab consists of a thin double-near-zero (DNZ) slab with an obtained tuned index of 0.05 and thickness of 0.04 lambda(0) coupled with a high-index dielectric slab with specific thicknesses. Through a parametric study, the non-zero index of the DNZ layer is tuned to create a clear image when it is coupled with the high-index dielectric layer. The minimum size for the aperture of the proposed two-layer slab is 2 lambda(0) to provide a clear projection of the two slits. The space between the slits is lambda(0)/8, which is five times beyond the diffraction limit. It is shown that, through the conventional methods (e.g., only with high-index dielectric slabs, uncoupled with a DNZ layer), it is impossible to clearly project slits at a large distance (similar to lambda(0)) due to the diffraction limit. An analytical analysis, as well as numerical results in a finite-element-based simulator, confirm the function of the proposed structure.

Automated summary

This paper introduces the use of tuned near-zero-index materials for subwavelength projection for the first time. A novel structure composed of a two-layer slab is proposed for long-distance projection of closely spaced objects with subwavelength separation. By adjusting the relationship between the near-zero-index material and the high-index dielectric slab, clear image projection is achieved.