Fundamental Research On Surface Plamon Resonance Sensor Based On Waveguide Structure

Surface Plasmon Resonance(SPR)sensor has been the concern of many researchers,with the excellent performance of high sensitivity,fast detection speed,real-time analysis in biological detection.So far,many companies have developed a variety of commercial SPR sensors.Although the traditional SPR sensor has the incomparable advantages of other sensors,because of the low resolution of conventional SPR sensors,it has been unable to meet the high demands of biological research and medicine.The resolution of Coupled Plasmon-Waveguide Resonance is higher than the traditional SPR by an order of magnitude,a smaller amount of refractive index change can be detected.Under the angle modulation,the refractive index curve of the SPR sensing structure of the traditional three-layer structure(measured object / metal / medium)is wide.As the reflectivity curve is wide,when the measured object refractive index changes smaller,the resonance angle of the amount of movement can't be accurately determined.In this paper,Long-Plasmon Range Surface Resonance and Couple Plasmon-Waveguide Resonance are studied in order to improve the detection limit of the sensor.In the LRSPR structure,a layer of magnesium fluoride waveguide between the dielectric layer and the metal layer is used as buffer layer,the influence of the thickness of the metal layer and the magnesium fluoride waveguide layer on the reflectance curve(resonance angle,half width and resonance depth)is studied.The preferred configuration for the metal and the magnesium fluoride layers is as follows: the silver film's thickness is 40 nm,the magnesium fluoride film's thickness is 800 nm;the gold film's thickness is 30 nm,the magnesium fluoride film's thickness is 700 nm.Especially for the gold film structure,under the optimal configuration,the half-band width of resonance curve is 0.87o.In the CPWR structure,a waveguide layer between the metal layer and the object to be measured was introduced.The effects of magnesium fluoride waveguide and silicon dioxide waveguides on the reflectance curves were studied.Through the study,we find that if the thickness of the waveguide layer is 10 nm,the CPWR reflectivity curve is not affected.The waveguide layer can protect the silver film from being oxidized in the silver film structure.In the gold film structure,when the thickness of the magnesium fluoride waveguide layer is 700 nm,a new narrow absorption peak appears in the reflectance curve,the half-band width of resonance curve is 0.38o,effectively improving the resolution of the sensor.