Appl. Phys. Lett. 114, 111101 (2019)

Negative-index media are typically made by introducing simultaneous negative permittivity and negative permeability to a system. Now, Simon Yves and co-workers in France claim to have demonstrated a negative-index metamaterial medium that they say is based on just negative effective permittivity and unit cells of resonator pairs supporting a dipolar resonance. The experiments were conducted in the microwave regime at ~4.7 GHz wavelength using quarter-wavelength (16 mm tall) resonators, formed from 1-mm-diameter metal rods, on a ground plane. The team investigated two different approaches: either displacing the position of one of the resonators in a pair, or detuning one resonator. A multiple-scattering-induced dipolar resonance was demonstrated, revealing a negative-effective-index region. The medium was shown to be able to support ‘superlensing’ of point sources of light; the approach may offer relatively low-loss subwavelength imaging as it is not, in principle, necessary to use metals. It is important to note that although the structure is periodic and resembles a photonic crystal, the array period is on a much smaller spatial scale.