| Terahertz(THz)wave is a kind of electromagnetic wave with a bandwidth in the range of 0.1-10 THz.It is connected with microwave in the low frequency band and infrared in the high frequency band.THz has been discovered as early as the early 19th century,but people’s research on THz is limited due to the lack of corresponding detection devices.Since the 1980s,with the gradual exploration of THz band,its unique physical properties have been gradually explored and widely used in security monitoring,remote sensing communication,environmental monitoring and many other fields.Then researchers found that its radiation energy is small,without destroying biological macromolecules and other substances,and can cover its characteristic spectrum,so people proposed that it can be used in biomedical nondestructive testing.With the emergence of various difficult and complicated diseases,it is particularly important to make timely diagnosis at the early stage of diseases.Traditional methods such as X-ray,nuclear magnetic resonance and circulating tumor cell detection have the limitations of great damage to the human body,low detection efficiency and high cost.Therefore,THz optical fiber bio detection technology has been favored by researchers in the field of biomedical detection in recent years by virtue of its advantages.Compared with traditional electrochemical biosensors,porous fiber-based biosensors have the advantages of anti-interference,corrosion resistance,miniaturization and high sensitivity,so they have attracted extensive attention from researchers.In this paper,several new terahertz holey fibers are proposed based on low loss polymer materials and different sensing mechanisms.On the basis of theoretical derivation,a series of simulation and corresponding experimental research and exploration are carried out.The main research content of this paper is as follows:1.Based on the full vector finite element method,a porous optical fiber sensing model with total internal reflection as transmission mechanism is optimized.The sensor performance is optimized and analyzed by adjusting the optical fiber structure parameters.The simulation results show that at 0.9 THz frequency,the fiber can obtain a sensitivity of 99.8%,and the confinement loss is kept around 10-12,which can show good biological sample recognition ability.2.The structure and working principle of Stereo lithography Appearance 3D printer are introduced.Using polymer photosensitive resin(refractive index=1.651)as the substrate material,the quasi-optimized optical fiber structure was prepared by photocuring 3D printing technology,and the terahertz time-domain spectroscopy system was used to test the optical fiber in the hollow state and filled with biological samples respectively.The experimental results show that the optimized design of terahertz fiber has certain feasibility in biosensing detection.3.Based on the full vector finite element method,a D-type fiber biosensing model with surface plasmon resonance as transmission mechanism was optimized.The model uses multilayer graphene as plasma excitation material,and obtains a maximum frequency sensitivity of 1300 GHz/RIU in the refractive index sensing range of 1.1-1.5,corresponding to a resolution of 9.6×10-4 RIU.The results show that this model has a broad application prospect in improving the sensitivity of biosensing detection. |
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