A Research On Nanometer Silver Locally Enhanced SPR Biosensor

Coupled plasmon-waveguide resonance?CPWR?uses the evanescent wave at the waveguide boundary to excite surface plasmon polariton?SPP?,which couples the energy of the optical field in the waveguide to surface plasmon wave to produce surface plasmon resonance?SPR?.In this paper,the BK7 prism was combined with Ag/a-SiO₂structure,and Ag nanoparticles were embedded on the surface of a-SiO₂ waveguide layer to form a new CPWR biosensor with Ag/a-SiO₂/a-SiO₂:Ag structure.The local surface plasmon resonance?LSPR?excited by Ag nanoparticles under the light wave field was coupled with CPWR resonance to enhance the characteristics of the biosensor.By adding a thin electrode?ITO?to the original structure,the metal Ag will undergo electrochemical metallization?ECM?effect under the action of electric field,so as to affect the change of the characteristic index of the biosensor.The main conclusions are as follows:Firstly,Under the wavelength mode detection method,the new CPWR biosensor with Ag/a-SiO₂/a-SiO₂:Ag structure has a LSPR effect due to the fact that the Ag nanoparticles in a-SiO₂:Ag will produce LSPR effect,so the characteristic indexes of this new CPWR sensor are better than that of the CPWR sensor without Ag nanoparticles,specifically,the resonance depth increases,the sensitivity increases,and the figure of merit increases.Secondly,Both Ag/a-SiO₂/a-SiO₂:Ag/ITO and Ag/a-SiO₂:Ag/a-SiO₂/ITO show ECM mechanism,although the resonance depth,FWHM and figure of merit of the biosensor become worse at this time.However,it is also proved that the SPR biosensor with Ag/a-SiO₂:Ag/a-SiO₂/ITO structure can realize the tuning of characteristic index under the condition of positive and negative bias.