The Study On SPR Technology Based On Long-range Surface Plasmon And Waveguide Structure

Surface Plasmon Resonance (SPR) technology with the advantages ofsamples without purification, label-free, fast detection speed and real timeanalysis, can be applied in the health, biological, food, environmentalmonitoring and other fields, so it became one of the hot topics of research.However, the SPR curve of the conventional structure (CSPR) with three layersis relatively wide under the angle modulation mode, it is difficult to determinethe resonance angle accurately. When the change of refractive index of themedium is small, it is also difficult to determine the change of the resonanceangle accurately. In this work, for the purpose of solving this problem,Long-Range Surface Plasmon Resonance (LRSPR) structure and the CoupledPlasmon-Waveguide Resonance (CPWR) structure were proposed, using themagnesium fluoride dielectric film as buffer layer and waveguide layerrespectively, the sensing performance of the two structure were compared withthat of CSPR under the mode of angle modulation, light intensity modulationand phase modulation modes, the main contents are as follows: 1. To detect the small changes of the refractive index of aqueous solution,the LRSPR resonance structure and the CPWR resonance structure wereproposed, magnesium fluoride films were used as the buffer layer andwaveguide layer, respectively. Compare with the CSPR structure. The SPRcurves are much narrower than that of CSPR structure.2. The optimal thickness of metal film and magnesium fluoride film in thethree kinds of structures were calculated. The optimal thickness is as follows:For CSPR, the thickness of gold film is50nm, the thickness of silver is55nm;For LRSPR, the thickness of gold film is30nm, the thickness of the magnesiumfluoride film is700nm (the thickness of silver film is40nm, and the thicknessof magnesium fluoride film is700nm), For CPWR structure, the thickness ofgold film is50nm, the thickness of magnesium fluoride film is700nm (thethickness of silver film is55nm, the thickness of magnesium fluoride film is700nm).3. The resonance curves and sensing performance were compared of thethree kinds of optimal structures under the mode of angle modulation, lightintensity modulation and phase modulation, respectively. Results show that theimaging sensitivity of LRSPR and CPWR structure were improved under lightintensity modulation. The imaging sensitivity can be as large as225.3forAg-LRSPR and603.9for Ag-CPWR, this is much larger than that of CSPR, TheLRSPR exhibits excellent sensing performance, but we can’t find the appropriateobservation angle to detect the change of phase in the CPWR structure, which we will focus on.