Low-loss planar metamaterials electromagnetically induced transparency for sensitive refractive index sensing

A low-loss and high transmission electromagnetically induced transparency like (EIT- like) structure is experimentally and numerically demonstrated in this paper. The proposed planar structure based on EIT-like metamaterial consists of two separate split-ring resonators, and its resulting transmission level can maximally reach 0.89 with significant suppression of radiation loss. According to the effective medium theory, the imaginary parts of the effective permittivity and permeability of the metamaterial are used as the evidence of low-loss. In the analysis, the simulated surface current, magnetic field distribution and coupled oscillator model reveal the principle of high transmittance EIT-effect. Furthermore, the peak of transparency frequency is highly sensitive to the variation of refractive index in the background medium. The sensor based on the proposed EIT structure can achieve a sensitivity of 1.69 GHz/RIU (refractive index unit) and a figure of merit of 11.66. Such metamaterials have potential perspectives in sensing and chiral slow light devices.