Metamaterial Sensor With Large Incident Angle Based on Electromagnetically Induced Transparency Effect

A metamaterial sensor with a large incident angle, based on the electromagnetically induced transparency (EIT) effect, is proposed. The proposed metamaterial sensor is a refractive index sensor, and the unit cell consists of a cut wire (CW), two split ring resonators (SRRs), and a metal plate. Due to the added metal plate on the side of the unit cell, the metamaterial sensor can tolerate a maximum incident angle of 75°. The transmission spectra with different incident angles show that the metamaterial sensor exhibits excellent performance at the large incident angle. The near-field coupling between SRRs and CW is explained by a three-level
$\Lambda $
-type system of bright-dark coupling, and the transmission spectrum calculated by the two-particle model is in keeping with the simulated transmission spectrum. The influences of structural parameters on the amplitude and frequency of the EIT effect are discussed. Meanwhile, owing to the outstanding dispersion around the transparent window, the maximum group delay can reach up to 3.84 ps. The maximum values of sensitivity and figure of merit (FOM) are 0.221 THz/RIU and 1.000 RIU-1, respectively. Moreover, metamaterial sensor shows good sensing characteristics under different incident angles. Our work exhibits excellent potential to overcome the bottleneck of the small incident angle in the present metamaterial sensor.