Abstract
By verifying the electromagnetic response characteristics of graphene in the low terahertz (THz) band, a terahertz metamaterial sensor is proposed. The unit cell of the metamaterial sensor is a split ring resonator nested square ring resonator. The split ring resonator with four gaps is made of lossy metal, and the square ring resonator is formed by graphene. This structure can produce two high-performance resonant valleys in the transmission spectrum of 0.1–1.9 THz. The quantum interference between metal–graphene hybrid units also produces a reverse electromagnetically induced transparency (EIT)-like resonant peak between the two resonant valleys. Compared with the bimetallic ring resonator having the same shape and size, the sensor can dynamically adjust the position of the lower frequency resonant valley, thus, realizing the active tuning of the bandwidth and amplitude of the EIT-like resonant peak. The results demonstrate that the proposed sensor has a better sensing performance and can improve the detection precision by tuning itself to avoid the interference of environmental factors and the properties of samples. Combined with the advantages of convenience, rapidity, and non-damage of terahertz spectrum detection, the sensor has a good application potential to improve the unlabeled trace matter detection.
Highlights
A metamaterial is a new type of artificial electromagnetic material that has a characteristic of a singular electromagnetic response that cannot be found in the nature.1 This material is usually composed of periodically arranged sub-wavelength units with micron-scale gaps, which can realize the local enhancement of electromagnetic fields.2 It is quite sensitive to the change of the dielectric environment around the structure
Focusing on the design optimization and performance research of the sensor, we propose a terahertz metamaterial sensor with the periodic unit structure of the split ring resonator nested square ring resonator
The results show that the proposed structure achieves the maximum sensitivity, Q factor, and figure-of-merit (FOM), which can reach up to 282 GHz per refractive index unit (GHz/RIU), 32, and 9.02 under the condition that the Fermi level of graphene is 1.0 eV
Summary
A metamaterial is a new type of artificial electromagnetic material that has a characteristic of a singular electromagnetic response that cannot be found in the nature. This material is usually composed of periodically arranged sub-wavelength units with micron-scale gaps, which can realize the local enhancement of electromagnetic fields. It is quite sensitive to the change of the dielectric environment around the structure. There are several studies that completely replace the metal materials with graphene, realizing functional applications in the terahertz region, but these devices based on special patterns make it more difficult to manufacture, and in the process of modulation, frequencies of each resonant point in the transmission spectrum may be disordered with the change of the Fermi level of graphene, introducing additional noise and resulting in unnecessary modulation. In contrast to the previously reported EIT-like and Fano effect in terahertz metamaterial device design, the resonant peak of the sensor can be adjusted and controlled subjectively without changing the position of the high-frequency resonant point and other constrained conditions; it is more suitable for the field of sensing. It will not introduce additional noise in the modulation process to be studied and applied in more complex fields
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