High-transmission negative refraction in the gradient space-coiling metamaterials

In this work, we show that negative refraction with ultrahigh transmission can be obtained via gradient space-coiling metamaterials. By using a retrieval method for our design, we find that both the effective density and bulk modulus of metamaterials are simultaneously negative in the sense of the effective medium, accompanied by nearly perfect impedance matching. The negative refraction effects with the impedance matched prism and plate are numerically demonstrated, and the transmission coefficients are higher than 90% with the scattered-wave energy less than 4%. The numerical analyses of the subwavelength imaging effect of the superlens based on the proposed metamaterials are also presented, and the super-resolution beyond the diffraction limit and ultrahigh efficiency are evidenced.