A Research Of Terahertz Microfluidic Sensor Based On Gap-plasmon Enhanced Interaction

Due to its unique properties,terahertz spectroscopy provides an efficient,low-cost,convenient,spectral analysis method for various fields,such as food safety testing,biological identification,production monitoring and environmental monitoring and so on.However,the widespread use of terahertz sensor is hampered by the low sensitivity and mismatch between biomolecule scale and terahertz wavelengths.In recent years,metamaterials?MMS?based sensors with a meta-reflector gap structure have been demonstrated characterized strong localized and enhanced EM fields,which is highly sensitive to the dielectric properties of the surrounding environment,providing an ideal platform for biosensing.Up to date,most of terahertz metamaterial biosensors are limited to dry or partially hydrated specimen.Besides,the sensitivity still needs to be improved due to the imperfect spatial wave-matter overlap,which resulting in the utilization of electromagnetic energy is not maximized.Aiming on these problems,this dissertation focuses on a research of terahertz microfluidic sensor based on Gap-plasmon enhanced interaction.High sensitivity sensing on biological liquid samples has been achieved by combination of dipole/Fano induced trapped mode and Gap-plasmon transverse resonance.The main research work as follows:?1?Begin with massive related reference study,we have studied the properties of metamaterials and the resonant modes of different metasurface structures,such as:Split resonant ring?SRR?,absorber,Electromagnetic induced transparency?EIT?,Fano resonance and Quadrupole resonance,etc.Meanwhile,various types of terahertz sensors were investigated to understand the sensor structure design and basic principles.?2?According to the survey data,we have designed terahertz microfludic sensor based on Gap-plasmon enhanced interaction.After the comparison between the sensing types and the channel position,the final scheme was determined to be the reflective microfluidic sensing platform based on a maximized spatial-overlap channel in the metamaterial perfect absorber?MPA?,thus significantly enhancing the interaction between the electromagnetic energy and the analyte.The double-ring resonantor was adopted as the unit structure,which has the merits of polarization insensitivity and double resonances.The anti-parallel inner and outer loop currents distribution indicates the appearance of the Trapped mode,which dramatically suppressed radiation loss and enhanced the absorption.A microfluidic channel with the Gap-plasmon effect is formed in between the metal microstructure and the metal plane mirror,thereafter light-matter interaction and the EM field concentration in the absorptive channel are significantly enhanced.Compared with the on-top metaurface structure with the same resonant unit,the proposed sensor exhibit s much higher sensitivity and detection signal.?3?Optimized on the the original design,we further constructed a higher absorptive meta-mirror cavity with a hybrid dielectric-metal-atom resonator array through deep the etching process to expand the strong interaction region,which obviously improved the sensitivity.?4?To our best knowledge,we firstly developed the equivalent circuit theory for the dual-band absorptive microfluidic sensor.After retrieval of the accurate circuit parameters,the sensor has been throughly analyzed from the perspective of the circuit theory.?5?By using the 1^stDebye Model,the sensing performance for the bovine serum albumin?BSA?samples of different solutions have been characterized in simulation.Finally,the micro-processing and the spectrometric measurement have been completed on the terahertz time-domain spectroscopy?THz-TDS?.The good accordance between the simulation and test results indicate the promising application of the promote sensor.