| Metamaterials refer to a kind of artificial materials consisted bysubwavelength unit cell with periodically arrangement, it has been used inclusivelyin various functionalized devices such as sensors, super lens, cloak and so on, resultfrom its distinctive electromagnetic properties that lots of natural materials can notachieve. Split ring resonators (SRR) have been applicated widely as a fundamentalcomponent element to achieve functionalized devices because of the localelectromagnetic field enhancement and high quality factor, etc. Metamaterials canproduce transparent resonance phenomenons and resonant modes that is notsupported in symmetric configurations by breaking the symmetry of the unit cell,such as the Fano resonance, electromagnetic induced transparency (EIT) and theplasmon hybrid. Asymmetric SRRs were demonstrated to be able to produce theresonance with narrow linewidth and high quality factor and have a variety ofapplications, including a notch filter, a narrowband terahertz emitter with highselectivity and terahertz sensitive biological&chemical sensors. This paper haspresented a study of the fabrication crafts of planar metamaterial devices, the designdetails of multiple asymmetric split ring resonators and the analysis of transparentresonance effects. The main work of this paper contains four parts as follow：(1) A method for fabricating metamaterial terahertz devices with laser induced andnon-electrolytic plating with copper using a semiconductor laser (405nm) wasproposed. Compared to the fabricating technique utilizing ultraviolet laser, ourproposed method possesses the advantages of low equipment, energy cost and highcost-effective. Its feasibility has been vetified by fabricating and characterizing themetamaterial terahertz devices and the minimum metal width fabricated is about5μm.(2) A terahertz resonator with EIT-like effect was designed and fabricated, thestructure of which consists of two asymmetrically arranged split-ring resonators.Using finite difference time domain (FDTD), the transmission and refractive-index -based sensing performance of resonators were investigated and simulated.Simulation results show that the resonator exhibits high sensitivity of75GHz/RIUand figure of merit (FOM) of4.4, much higher than the individual SRR sensors.After being measured by THz-TDS for transmission property, the resonator shows asharp transparent peak near0.52THz, the resonance strength and Q value of whichare determined by relative distance between two asymmetric SRR. The experimentalresults are in good agreement with simulations.(3) The simulation study of the EIT-like phenomenon in a terahertz resonatorconsists of SRR and metal wire has been completed. The dark mode in SRR isexcited by metal wires act as bright resonator. Due to the different spatial distributionof the metal wires, the direction of induced surface current in SRR is sensitive topolarization. By controlling the polarization of the incident electric field, we canachieve the EIT switch based on plasma.(4) A terahertz metamaterials resonator with EIT property was designed andfabricated, the unit cell of which is consisted by a pair of bright and dark split ringresonators atoms. The coupling strength between two “atoms” can be enhanced ifonly two atoms are connected to produce the conductive coupling. Presented insimulation and calculation, the highest resonant Q value is up to90. Moreover, thesensitivity of refractive index and FOM are61.7GHz/RIU and10.74, respectively. Atlast, the resonator sample of “connected SRRs” was fabricated, the transmissionproperty of which was characterized by THz-TDS. |
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