We propose a dual-band terahertz metamaterial sensor (MS), which exhibits the low loss and high quality (Q) factor of electromagnetically induced transparency (EIT) effects at the frequencies of 0.89 THz and 1.56 THz simultaneously. The physical natures of EIT effects are analyzed by using numerical simulations and a “two particle” model. Further, THz sensing is performed based on the shifts of two EIT resonances when the analyte is coated at the metamaterial surface. The sensitivities of the sensor are investigated with respect to different thicknesses, cover areas and refractive indexes of the coated analyte film. Results show that the first EIT resonance is suitable for sensing the analyte with the refractive index from 1.5 to 2, while the second EIT resonance is more suitable for sensing the refractive index of the analyte from 1 to 1.5. The sensitivity is 280.8 GHz/RIU, the average Q value is 14.3, and the figure of merit (FOM) value is 4 for the first EIT resonance. Meanwhile, the sensitivity is 201.6 GHz/RIU, the average Q value is 56.9, and the FOM value is 11.5 for the second EIT resonance. Such a metamaterial sensor with high refractive index sensitivity and dual-band would have great potentials for promoting the developments of multi-band/broadband terahertz sensing and detection technology.

We propose a metamaterial sensor based on electromagnetically induced transparency (EIT) effect, which is composed of two elliptical structures with splits. Based on the coupling of bright and dark modes, a low-loss transparent window is realized at 1.88 THz. Surface current distribution and equivalent circuit model are used to analyze the physical mechanism of the EIT effect. In addition, the sensitivity of the sensor is investigated for different thickness and refractive index for analyte. The simulation results show that when the analyte thickness is 15 μm and the refractive index is between 1 and 1.5, the sensitivity of the sensor is as high as 450.7 GHz/RIU, and the figure of merit (FOM) value is 7.7. And when the refractive index of analyte is 1.5 and its thickness is between 0 and 5 μm, the sensor can also be used for thickness sensing with a sensitivity of 40.8 GHz μm−1. In addition, the proposed metamaterial sensor can be used to simulate the detection of sodium chloride solution, and the sensitivity is 66.2 GHz/ mol d m 3 . These above features indicate that the proposed structure paves the way for designing high-sensitivity EIT sensors in the terahertz region, which plays important roles in promoting terahertz sensing and detection technology.

To realize the electromagnetically induced transparency (EIT) or reflection (EIR) effect in the terahertz band, many metamaterial structures have been proposed. However, these structures usually have a single function of EIT effect or EIR effect, and it is a major challenge for a metamaterial structure to perform multiple functions. In this study, a switchable multifunctional hybrid metamaterial is proposed, which realizes the combined function of tunable EIT effect and EIR effect at THz regions through the integration of vanadium dioxide (VO 2 ) and metal metamaterial. Moreover, by changing the conductivity of VO 2 , the intensity modulations of EIT window and EIR window reach 36.11% and 50.59%, respectively. The surface current distribution and electric field responses are used to analyze the physical mechanisms of the EIT effect and the EIR effect. In addition, the active tuning mechanism of the metamaterial is theoretically explored based on the "two-particle" model. The designed hybrid metamaterial provides a simple approach to realize tunable EIT effect and EIR effect in THz metamaterials. This work opens up a possible way to achieve switchable functions (EIT or EIR) in a single device, which may find potential applications in optical switches, sensing, filtering, and slow light devices.

In this study, we design an electromagnetically induced transparency (EIT) effect based on a metamaterial sensor composed of three split-ring structures in the terahertz range. The EIT transparency window appears at 1.83 THz due to the electromagnetic coupling between the three split-rings. To analyze its physical mechanism, we use the ‘two-particle’ model and obtain good consistency between the simulation and theoretical results. The simulation results also show that when the thickness of the measured object is 15 μm and the refractive index is between 1 and 1.5, the refractive index sensitivity of the sensor is as high as 423.9 GHz RIU−1, and the figure of merit value is 6.9. In addition, the sensor is used to simulate the detection and distinction of different types of microbiota. We expect that this work will pave the way for designing high-sensitivity EIT sensors in the terahertz region and promote the development of terahertz sensing and label-free detection of pathogens.