Research On Multi-Resonant Terahertz Metamaterial Biosensor

Metamaterials are a new type of artificial composite electromagnetic material composed of subwavelength unit cell array periodically arranged.It can exhibit exotic electromagnetic properties unavailable in natural materials,such as negative refractive index,negative dielectric constant,and reverse Doppler effects.In particular,resonant metamaterials have microsized gaps,and can give rise to significant enhancement of local fields,which are particularly sensitive to the change in the dielectric properties of the surrounding environment.Therefore,the resonant metamaterials can exhibit promising application in sensing filed.Simultaneously,the terahertz wave has the relatively low photon energy and can excite the collective oscillation mode of biomolecules,as enhancing the sensitivity in detecting biomolecules.In addition,most of biomolecules have the specific fingerprint in terahertz range,which can exhibit unique advantages in detecting and identifying biomolecules.Based on above reasons,two different multi-resonant terahertz metamaterial biosensors are designed in this thesis,which are the complementary dual-resonant terahertz metamaterial biosensor and the absorber-based tri-resonant terahertz metamaterial biosensor.Numerical calculations HFSS based on the finite element method are performed to evaluate and optimize the sensitivities of two biosensors.The main research work of this thesis is as follows:1.A dual-resonant terahertz metamaterial biosensor based on complementary structure is designed and its unit cell is composed of annular gap arrayed periodically.In the numerical simulations,the structural parameters of the biosensor are optimized,and the distributions of the surface current and electric field are monitored.The distributions of the surface current and electric field demonstrate that the two resonances originate from the LC resonance and electric dipole resonance,respectively.Based on these,the influences of the thickness and refractive index of the analyte on the sesnitivity are analyzed.The calculated results show that the biosensor is distinct sensitive to the refractive index and thickness of the analyte.Moreover,its sensitivity is much higher than that of the single resonant metamaterial sensor.2.Due to the absorption peak of metamaterial absorbers with narrow FWHM and high sensitivity to the change of the external environment,a three-resonant biosensor based on the terahertz metamaterial absorber is designed and its unit cell is composed of upper and lower symmetric dual-SRR.In the numerical simulations and calculations,the structural parameters and electromagnetic characteristics of the terahertz metamaterial absorber are optimized to understand the absorption mechanism of this absorber,and the corresponding sensing performances are analyzed and calculated.The surface current and power flow distributions demonstrate that the three resonant modes originate from the LC resonance,four dipole resonance and electric dipole resonance,respectively.Calculation results show that the three resonant modes can exhibit high absorption and sensitivity.Moreover,their sensitivities are much higher than that of the multi-resonant metamaterial sensor by combining or stacking.