A Biosensor With Long Range Surface Plasmon Resonance Effect

In recent years,surface plasmon resonance has become the most reliable and sensitive principle among available optical technologies.It is widely used in environmental detection,biosensors,medicine and food safety,temperature and pressure detection,and other fields.The detection of biomolecules does not require pre labeling,and can be quickly and real-time used in explosive environments.It has electromagnetic interference resistance and biocompatibility.However,traditional Surface Plasma Resolution sensors have relatively low sensitivity,large Full Width at Half Maximum,and shallow penetration depth,which cannot meet the size of biomacromolecule analytes,resulting in poor measurement accuracy.In order to improve the sensitivity of the sensor and the penetration depth of biomolecules,this paper proposes a new biological sensing concept based on the Long-Range Surface Plasma Resolution principle and the tunneling effect caused by FTIR.A multilayer sensing structure（prism/Cytop/Al₂O₃/Ag/Al₂O₃/sensing medium/air）excited by LRSPR is designed,FTIR refers to when incident light propagates from a high refractive index dielectric layer to a low refractive index dielectric layer,and when the incident angle is greater than the critical angle（total reflection angle）,if the thickness of the low refractive index dielectric layer is less than the penetration depth of the evanescent wave,light can break through the total reflection limit and enter the next high refractive index dielectric layer to form transmission.The sensing structure relies on this optical physical effect to stimulate the transfer effect of plasma wave energy on the metal surface,which is not concentrated on the metal surface,but transferred to the interior of the sensing medium.By using the finite element simulation software COMSOL,the performance of the sensing model in this paper under angle modulation and wavelength modulation was tested.Under angle modulation,the sensing performance with an average minimum FWHM of 0.008°and an average quality factor of 10296/RIU was achieved,as well as the effect of a maximum sensitivity of 170000nm/RIU under wavelength modulation,with an average sensitivity of 108570 nm/RIU in the range of 1.3401 to 1.3408,and a maximum quality factor of 11333/RIU.On this basis,this paper also verifies the resonance curve characteristics of the model,the optimal matching film thickness to maintain the highest sensing performance range,and the variation of the resonance curve with various parameters.