Preparation, Measurement And Simulation Of Dual-band Terahertz Metamaterials

With the rapid development of terahertz(THz)technology and metamaterial science,THz metamaterials have been widely studied from single-to multi-band and even broadband.In addition,THz functional devices based on metamaterials have been widely proposed and demonstrated,such as filters,sensors,modulators,absorbers and so on.In this work,we use UV lithography,terahertz time domain spectrometer and electromagnetic simulation to study the dual-band filter,Fano resonance and strong coupling between resonance modes in THz metamaterials based on asymmetric split ring resonator.The main results are as follows:?.Investigation of dual band THz metamaterials based on double C-type split ring resonatorsThe single-and dual-band THz metamaterials are realized by reassembling the basic components of C-type split ring resonators with different sizes.Three samples were prepared by photolithography and electron beam vacuum evaporation,and the transmission spectrum was measured and electromagnetically simulated.The results show that the large/small C-type split ring resonators produce resonances at1.06/1.25 THz,respectively.While,there are two resonances at 1.09 THz and 1.34THz for the double C-type split ring resonator,respectively.Therefore,the resonant frequencies can be adjusted flexibly by combining C-type split ring resonators of different sizes,and even work with multi-band and broadband.?.Investigation of THz Fano resonance in asymmetric split ring resonators based on square ringFano resonance is produced by introducing two asymmetric“gaps”into the square ring split ring resonator.Two resonators with symmetric and asymmetric“gap”positions were fabricated by UV lithography and ion beam etching,the transmission spectrum was measured and electromagnetically simulated.The results show that only 1.07 THz LC resonance appears in the transmission spectrum for symmetrical positions of the“left”and“right”gaps.For the asymmetric left/right gaps,a new Fano resonance will appear in addition to the LC resonance.When the offset of the left gap is 7.5?m,LC and Fano resonances appear at 1.06 and 1.12 THz.Our findings are helpful for the application of Fano resonance based on metamaterials in optical devices,such as notch filter,narrow band filter,optical switch device,slow light device,etc.?.Strong coupling between dipole and lattice modes in asymmetric split ring resonatorThe coupling phenomenon between different resonance modes in asymmetric split ring resonator is studied by electromagnetic simulation.It is found that the breaking of spatial symmetry can lead to the coupling between dipole and lattice modes,and the splitting between the two modes is proportional to the unit size L and the splitting arm width G;inversely proportional to the line width W;almostly independent of the splitting gap t and the line width W₁of the connecting lines.When W=2?m,L=86?m,G=60?m,and P=183?m,the coupling strength between dipole and lattice modes reaches the“strong coupling”regime.The results offer an avenue to invoke lattice induced transparency,high-Q resonances,and strong field confinement,which could find applications in designing slow light devices,ultrasensitive sensors,and multiband narrow filters.